This is such a great and clear explanation! It is very important to be informed about this topic, since it concerns us all. The only question I have left from the video is why is it said then that CH4 is a more potent greenhouse gas than CO2?
Thanks much for your question. In looking back at the video, I can see now that some of my statements regarding CO2 vs CH4 needed clarification. The question of CO2 versus CH4 & HFC’s (etc) radiative forcing is complex and I needed to better explain that (!) as follows: There are several points that need to be considered: 1) The usual comparison of CO2 and CH4 potency for radiative forcing is per unit mass, usually kg, which already skews the data, as follows: for every 1 kg of CO2 and 1 kg of CH4, there are 44/16 or 2.75 times more CH4 molecules than CO2 molecules per unit mass. So using mass immediately skews the comparison due to it not being an equal amount of CH4 and CO2 molecules. (44 and 16 are the periodic table masses CO2 and CH4.) 2) It is true that in comparing kg to kg, methane (and HFCs, etc) are way more potent than CO2. However in practice, that particular factoid about kg CO2 vs kg CH4 doesn’t matter because CO2 has several orders of magnitude more kilograms in the atmosphere. So the kg-for-kg factoid leads the broader public to not worry enough about CO2 emissions versus public worry about CH4 emissions. We should worry about the overall potency (volume-to-volume x number of molecules per unit volume), not the kg-for-kg statistic. 3) The statistic generally arrived at on an internet search comparing the radiative forcing of the two gases is from EPA data that states CH4 is 25x more powerful than CO2. This is a tricky calculation, and is given per 100 years for a given equal mass of CO2 and CH4. A few complications-CH4 half life is ten years, CO2 half life is hundreds of years (could not pin that down, several reputable sources gave a large range); the time span of the calculation (100 years) is a huge consideration because of the large difference in half lives; the half life of CH4 is due to its oxidation into CO2, which adds a small (by comparison) amount of CO2 to the total; and finally, the calculation avoids the all-important consideration of actual amount of molecules of CO2 versus CH4 present in the atmosphere. 4) I think the reason the kg-for-kg factoid entered the discourse is that it is necessary to explain one thing - namely why methane leakage from the gas/oil industry is so much worse than just combusting it into CO2. If methane and CO2 were equally "potent" on a molecule-for-molecule basis, then methane leaks from, e.g., natural gas pipelines, wouldn't matter for climate change. But leaks do matter, because a mole of (uncombusted) methane creates far more radiative forcing than a mole of CO2. 5) This 2016 data is from the site ourworldindata.org/greenhouse-gas-emissions#annual-greenhouse-gas-emissions-how-much-do-we-emit-each-year: In terms of CO2 equivalents (CO2eq) (GHGs are converted to CO2eq by multiplying each gas by its 100 year 'global warming potential' value: the amount of warming 1 ton of the gas would create relative to one ton of CO2 over a 100 yr time scale): CO2 74.4%, CH4 17.3%, and HFCs 2.1%. This is what I was getting at in the video without explanation, except there is a much larger difference than indicated here, since, again, the comparison here is between masses rather than actual numbers of molecules (per given volume of air), the latter giving the real result in terms of comparing radiative forcing. Thanks for bringing up this question. I’ll have to edit out some of those statements, as they are misleading in terms of how they are phrased in the video. (RUclips hugely restricts editing of a published video, I’ll give it a try.)
@@CrashChemistryAcademy Thanks for that. These are issues I certainly would not have considered because no one seems to talk about it! Your explanation of mass:mass versus molecule:molecule considerations, and that of half life significance, is especially appreciated (and interesting).
Thank you for this clear explanation. As a physicist, I have never understood why people with little or no understanding of the basic physics of the process should have such strong opinions about it, and why we, as a country, empower such ignorance and allow it to deter us from necessary action. This extreme arrogance based on ignorance may will impoverish our grandchildren.
I don't know. There almost seems to be a cult of self-righteousness taking over-- people love that heady sense of knowing they're right and you're wrong, and what you have to say is irrelevant. It's a weak position from which to hold a conversation or to learn about what is going on in the world.
Thanks so much for a very gratifying comment. You should know (if you haven’t already noticed) that I pinned a previous comment and my answer regarding the potency of CO2 versus CH4, something that was not well considered in the video narrative.
The best, detailed video on how and why CO2 causes global warming I've seen to date. There is sooo much misinformation and misinterpretation of how CO2 causes climate change out there and refutations based on those strawmans, its painful. Thank you for this.
This is absolutely phenomenal, I mean of course not the condition of the world but the video. This is such a clear explanation of the science behind global warming without making a person have to research on 50 something websites for the same information. And the clarity with which it has been explained is something I cannot put into words. Thanks a ton!!
Super underrated video! If only people could dedicate 45 mins of active listening to watch this video (especially the extremists on both ends of the global warming spectrum), we could eliminate most of these polarizing arguments, most of which do not even mention the science. This is one of the reasons why I love STEM: it provides ground truth within a sea of lies and misconceptions.
I had some ideas of how global warming occurred but this presentation hugely clarified everything I was trying to understand, as well as going far beyond what was, for me, the basics of how all this works. Thanks so much for posting this. It is essential for the entire world.
Videos like this are so incredibly important. Thanks for posting this-- I had no luck finding anything about the greenhouse mechanism other than difficult science or dumbed down videos (all basically just saying that greenhouse gases act to put IR energy back into the earth, i.e., the usual "greenhouse gases act like a blanket" and nothing else). This was most edifying and exactly at the right level for anyone who wants to get to an accessible depth with this. Again, so important to bring this information to a general audience.
Great video. As good as it is, I have to say it sets my teeth on edge hearing anyone say "a warmer atmosphere holds more water vapor" since this is a complete misrepresentation. It really sticks out in this video, which is so thorough otherwise and not trying to be too simplified. How do you know that "a warmer atmosphere holds more water vapor" is false? Because you'd get the same increase of water vapor with temperature even if there were no oxygen or nitrogen or any other atmospheric gases available to "hold" the water vapor.
I guess I'm not quite following. Are you saying if the atmosphere were made of different gases that it would still be able to increase maximum water vapor at higher temps? Or did I not get that right? At any rate, our atmosphere, at 25C and 100 % humidity (maximum possible water vapor), will have 30 molecules of water per 1000 molecules of atmospheric gases. At around the temperatures that the earth maxes out at, perhaps 40C, the maximum water molecules (100% humidity) goes up to about 40. Below 0C the maximum amount of water vapor (100% humidity) goes to below 1 molecule per 1000. I'm not sure how the word "hold" misrepresents that.
@@CrashChemistryAcademy Thanks for the quick reply. In the spirit of citing original sources, try googling "Alistair B. Fraser penn state bad meteorology" for a brief explanation (the first entry) and "water vapor myths Steven M. Babin" for a slightly more detailed one. I appreciate your taking the time to read this, I'm in the AGW field too and know how "interesting" some of the responses one gets can be. :)
Thanks so much! The Babin article was great-- it clarified the fuzziness I've had about the behavior of water vapor. I am not working in AGW, I am a high school chemistry teacher and made this video for my students. As a chemistry teacher this seems like something I should have known, or at least should have looked further into to alleviate my fuzziness, so thanks for the article! It is much appreciated. As for my statement in the video, I will let it stand since youtube has very few editing capabilities, as well as the significance that higher temperature can result in more water vapor being the salient point here.
Interesting but shows fundamentally wrong physics. There is no radiation transfer of heat in the athmosphere. It is only tranfered by convection in the high pressure at the surface. This means that the ammount of grean hous gasses have no impact of the surface temperature. The difference of temperature is related to the sunlight thats reaches the surface. As the difference in summer and winter far from the equator. The radiation is only valid in the stratosphere and higer altitudes. Also the mean temperature of the earth is derived form a flat surface whitch is not even close to the real shape of the earth.
This had been a good comment, one that seemed reasonable, until you stated that the earth is not flat. That is fundamentially incorrect, and really, when all is said and done, throws your entire argument into the toilet. You really had me going there.
Your problem is that a pirani guague proves that conduction dominates ir radiation on heat transfer by 249:1 at 1 atmosphere pressure. Here's another problem.actual greenhouses cool at night despite being transparent to incoming ir radiation therfore back radiation, if it exists, has no effect on the temperature of surface materials.
In addition to the higher emission altitude that averages about 5.5 km altitude (15km at 220 k for CO2, and 3.5km at 265 k for water vapor), the width of the absorption spectra also increases when the more insignificant 'outer edges' of these spectra becomes more significant with the a higher probability to absorb with more greenhouse gas molecules in the atmosphere. This narrows the atmospheric window, so that a broader emission spectrum to space at low temperatures will occur as well as a broader absorption spectrum near the surface increases the amount of absorbed radiant energy emitted by the surface. A very interesting and easy to understand video that is worth sharing.
@@grindupBaker You will be able to measure different widths and amplitudes of the atmospheric window depending on the height above the ground, but it is problematic to be able to know what you are measuring in this way. Since the greenhouse gases not only absorb IR radiation but also emit IR radiation (Because they have a temperature), a spectroscope will not only measure the radiation from the ground, but also from the atmosphere between the ground and the spectroscope. For that reason, you will be able to see a somewhat uniform radiation spectrum close to the ground, while measurements made higher up, let's say 8 km, will give a radiation spectrum that clearly shows the absorption spectra of the various greenhouse gases. These become more visible because the temperature in the atmosphere at 8 km altitude is much lower than at the surface. And where the greenhouse gases absorb at the ground, they will emit radiation from a low temperature at an altitude of 8 km. This results in pits or dips in the spectrum - because gases with a low temperature emit little effect. In contrast, the atmospheric window, the area of the spectrum where the atmosphere does not absorb anything (practically speaking), will be read with the same strength as the one you had measured near the surface. With increasing amounts of greenhouse gases, the atmospheric window will narrow. Conceptually, and if we think that we are moving the thermal spectrum into the visible part of the spectrum, the atmospheric window will essentially be transparent to wavelengths in the green spectrum. The imaginary green color will be mixed with orange and cyan, and will not appear as a sharp and pure green color, but if you increase the amount of greenhouse gases so that the atmospheric window narrows, the green color will become clearer and clearer, but not weaker. It does not become weaker because the surface which is now heated emits more power, and thus the power emitted through the atmospheric window must be distributed over a narrower spectrum. This increases the amplitude of the emission spectrum - which directly reflects the temperature rise on the surface. The water in the sea does not have such an atmospheric window. In addition, heat flow in the sea takes place primarily through conduction, but also circulation. But if you look at the thermal spectrum that the water surface emits, it will appear as an approximately black body where all wavelengths are somewhat evenly distributed in amplitude (within Planck's radiation curve). The emissivity of water is not 1, but around 0.95. So water deviates about 5% from being a black body in the thermal spectrum. Wavelengths around 50 um have little effect at the temperatures we normally have on earth, and constitute only 2.7% of the effect emitted by 10 um (peak wavelength at 15°C). Only 40TW of the heat energy from the Earth's interior reaches the surface. This corresponds to a flux of only 0.08W/m². At a surface temperature of 15°C (390 W/m²), the ground heat is responsible for only 0.014°C, and has no practical significance.
@@grindupBaker The emissivity varies a bit, ofcourse. Seawater and destilled water have different chemical properties, and also have different emissivity, but ball park figures is around 0,95-0,97. Also, the angle and the water temperature you measure have an impact on the emissivity. Speaking of the energy balance, also have in mind that if a substance has an emissivity of 0.95, it also has an absorptivity of 0.95. CO2 disolved in water do not contribute to any significant portion of what is emitted at 13-17 um. In this case, CO2 is a part of a fluid that already have a close approximity of a black body. In water, the molecules are tightly spaced. This allows the molecules to undergo quantum mechanical transitions way more often, and much more 'efficient' through collisions with each other than they do in a gas. This will broaden the absorption and emission spectra so much that the molecules absorb and emits almost like a black body. Take a look at the emission spectra for liquid water and water vapor. They are quite different. While liquid water have an emission spectrum that is close to a Planck radiation curve, water vapor have more distinct emission spectra peaking at 72um and 6.8um (within the thermal spectrum).
@@grindupBaker Emission spectra and absorption spectra are the same, given the same substance in its current phase (solid, liquid, or gas), pressure and temperature. If you haven't found emission spectra, you'll see them in the absorption spectra.
I had not seen mention to heat island effect even though absorb emits IR energy , trees , green , white color roofs reduce CO2 IR land energy heat absorbing
A common criticism is that the effect of warming from CO2 decreases with a log relationship to concentration. Can you explain how this affects feedback and climate sensitivity?
Great question! The physical chemistry of CO2 would not result in a decreasing radiative forcing (the imbalance between incoming and outgoing energy) by itself. However, one has to consider all the many variables present in the complex system of the earth-atmosphere, and the end result is an increase in the effect of CO2 on warming, not a decrease, as follows: Many of the variables involved here in the earth-atmosphere system can be summed up in the earth's carbon cycle. Before the 19th century, the concentration of CO2 remained fairly stable due to its involvement in the carbon cycle, and changes in the carbon cycle resulted in changes in CO2 concentration. As we increase CO2 concentration, the various carbon sinks that exist in the carbon cycle will remove much of that increasing CO2 (otherwise the current increase in CO2 concentration would be much more than what it now is). However, those carbon sinks have a limit, and so as we increase CO2 concentration those sinks begin to get less efficient, or more saturated, or however you want to think of it, and so the warming effect of adding CO2 increases as the carbon cycle gets less able to handle higher and higher CO2 concentrations, simply due to a higher rate of increase in atmospheric CO2. Once the carbon cycle is finally overwhelmed, which is called a tipping point, then we have a runaway greenhouse effect and the earth will boil away all its oceans. Although my guess is that the oceans will have already evaporated as we approach that tipping pint. This brings up the hydrologic (water) cycle, which again, will result in adding more water vapor (the most potent greenhouse gas) due to higher atmospheric temperatures caused by increasing CO2, and so this is one feedback that would also reach a tipping point. Regarding climate sensitivity, I think this is where the idea of a decreasing log relationship that you mentioned comes from. Climate sensitivity as you may know measures the change in mean temperature due to a changing variable that produces radiative forcing, such as increasing CO2. But that measure has two distinct endpoints. The first endpoint is the change in mean temperature the moment that variable (I'll just call it CO2) reaches a particular change, such as doubling in concentration. The second endpoint occurs due to the fact that the moment the CO2 reaches that doubling (and stops increasing in concentration) is NOT the point at which the earth stops warming. Due to the earth requiring many decades to get back to the equilibrium of its energy balance to relieve that radiative forcing, the earth will continue to warm decades after the CO2 has reached its doubling. This rate of warming decreases logarithmically as the earth eases toward the reestablishment of its energy equilibrium. So that logarithmic relationship has likely been seized upon by climate change deniers, skeptics, etc., to say that the effect of warming from CO2 decreases with a log relationship to concentration, which is incorrect. A simple analogy would be having a room at 10C with a water radiator in it. You turn on the boiler and set the thermostat to 20C. The boiler remains on until the thermostat reaches 20C, and then the boiler turns off (first endpoint is 20C). However the radiator will continue to release heat after the boiler turns off, resulting in a room temperature that is higher than 20C (second endpoint is >20C), until an equilibrium between the room temperature and the radiator temperature has been reached. (Note that 20C is not twice the temp as 10C, they are just two randomly chosen numbers.) Hope that all makes sense!
@JJ well, thermal radiation transmission is not instantaneous, there are many lags due to its speed, its interception by CO2, the lag in CO2 re-emission, the equal chance of re-radiation of infrared either back to the earth or release to space, etc, and in particular the CO2-water vapor feedback takes a while to equilibrate. All of this spells a lag for re-establishment of thermal equilibrium in the earth-energy system. Radiative forcing is only a measure of the difference in outgoing versus incoming energy, it is not a source of heat. It in fact can result in cooling, for example if albedo increases, then radiative forcing 'reverses', and the result is a decrease in temperature.
@JJ That seems to be correct. I guess I would like to clarify what is meant by thermal. The incoming and outgoing energies are electromagnetic radiation. They are only thermal insofar as they are able to interact with atoms and change their kinetic energy. Infrared leaving the earth is nothing more than infrared radiation. However when it is generated at the earth's surface by surface atoms' KE, that KE is reduced by the amount of energy contained in the IR photon. The IR photon itself is not heat. Likewise with sun energy. It is only thermal insofar as it is able to increase KE of earth's surface atoms that absorb it. This may be getting picky but I think it is important to distinguish electromagnetic radiation (which is not heat) from its effect on the objects it interacts with.
I think you miss a point about the minor greenhouse gases CH4 and N2O--they seem to be more powerful than CO2 because they absorb in what would otherwise be infrared windows, so they are less saturated than CO2 (I know CO2 isn't saturated at the edges of its absorption bands, but it is more so than the others).
@@joelweiner4156 Do you ever feel guilty propagandizing scientifically illiterate children with pseudo science designed and paid for by people who intend to frighten them into submission to a controlled economy wherein they will be exploited for the remainder of their lives? Your explanations are deceptions; the insulation response of any material including "greenhouse gases" is logarithmic. The children you propagandize do not understand this concept but perhaps you too are just reading someone else's propaganda that you also have no ability to comprehend. At 400 ppm CO2's insulation response is asymptotic and nearing complete saturation as an insulating agent. CO2 has never been a control agent for climate in the past even at 4000+ ppm so how can you convince the scientifically literate that it began to be one, but only by those who seek to control the economy; the roots of poverty and enslavement for the illegitimate enrichment of their controllers.
17:00 water vapor depends on air temperature which also related to land surface temp which relate to heat island effect in cities , black concrete , no green grass etc
@@grindupBaker Thanks for helping out!! Regarding the quote, I was referring to absorption of IR by GHGs does not in itself result in warming, due to IR being released by GHGs as well. So the increase in KE by IR absorption is countered by the lowering of KE by the release of IR. There may be a momentary localized warming, but that is all.
Although this video a bit long, but I really don't feel that long, because I enjoy it so much, but it also makes me wonder about why the morning air is so fresh while there is more CO2 in the atmosphere at night than the day time
Thanks! It takes several years for a change in atmospheric CO2 levels to effect the earth's average temperature. Also, we cannot biologically detect CO2 levels in the air unless they get high enough (perhaps above 2-3%) to begin affecting our blood pH, which would make us ill. The current CO2 level is at an average of 0.0042%, so that is too low to be detected biologically. Of course the earth's temperature would get too high for life to exist long before we got to 2 or 3% CO2. Great question!
@@CrashChemistryAcademy Trying to understand everything when I replayed this video. Then, I got another question. How does higher temperature still increased when the earth's albedo is decreasing
@@cathyny83 The earth's absorption of the sun's energy is the source of all warming that occurs on earth, and albedo gives us the amount of sunlight reflected back into space by the earth, in other words the sunlight that does not warm the earth. So less albedo means more sunlight absorbed, resulting in a warmer earth. In the discussion at around 9:35 about the meaning of the equation governing the relationship of incoming versus outgoing energy, it is (1 - albedo) that is the multiplier on the left side that determines the amount of sunlight energy absorbed by the earth. If albedo decreases, then the term (1 - albedo) increases, which results in an increase in T (temperature) on the other side of the equation. Does that make sense?
@@CrashChemistryAcademy In other words, is less albedo cause the amount of solar energy the earth absorbed decrease, that leads to higher temperature？Since the total solar energy equals to the earth's surface temperature, it seems that less albedo would not increase the temperature
@@cathyny83 I think you are misunderstanding the cause of albedo, the reflection of solar energy. This is mostly clouds, snow, ice, and to a lesser extent all other surfaces on the earth. Some sunlight reflects off these surfaces and goes back into space. That reflected light (albedo) is therefore not absorbed by the earth, and so cannot be used to warm the earth. If the amount of reflected light decreases (less albedo) that means more light will be absorbed by the earth. That greater absorbed light energy results in higher average temperature on the earth.
"Green" comes from the metaphor of how global warming works similar to how a greenhouse works. While the metaphor breaks down upon close inspection, the greenhouse has been kept to symbolize the warming of the earth. A greenhouse is a glass house where plants are grown and is kept warmer than the outside ambient temperature via sunlight, which is useful in cold winter weather. The breakdown of the metaphor is that the earth’s energy equilibrium is the reason we have the greenhouse effect in the first place, whereas a greenhouse will not reach an energy equilibrium with its surroundings. The contents (except air) of a greenhouse warms via sunlight. That warming is transferred to air inside the greenhouse via conduction. Without the glass, that warm air would convect away and an equilibrium would be reached. However, that warmed air cannot move past the glass, and so it stays in the greenhouse, keeping it warmer than its surroundings. The greenhouse depends on not reaching an equilibrium, which is the opposite of how the greenhouse effect works!
Don't forget, also, heat transfer from the surface to the air via evapotranspiration, which is actually several times the amount lost by conduction and (pure) convection.
Thank you for the great video. I am trying to understand better the transmission and absorption of up-going IR radiation, and the role of the atmospheric window. My understanding is that at every height in the atmosphere the atmosphere radiates as a black body. So at every height part of this spectrum of radiation can escape through the atmospheric window; at every height there is energy lost into space. You mention around 25:00 that it is a misconception that IR absorption directly increases temperature. My misconception is that the absorbed IR raises temperature, following which the energy is re-emitted as a spectrum of black body radiation, part of which would again be able to escape. Surely I haven't understood the processes and would greatly appreciate further explanation, or perhaps you can point me to a video/article explaining it further.
The term "atmospheric window" applies to those IR frequencies emitted by the earth that are not absorbed by any greenhouse gas (GHG). Most IR frequencies emitted by the earth are absorbed by GHGs, but there are a few "windows" of IR frequencies NOT absorbed by any GHG, and so those IR frequencies escape directly to space. The black body radiation you speak of is the IR emitted by any GHG in the atmosphere. Any IR frequency emitted by a GHG can be lost to space if it is going up AND no GHG is in its way to absorb it. So the higher the GHG is in the atmosphere, the less likely there will be another GHG in its path to space. Your misconception is not really a misconception. The absorbed IR will increase GHG KE, which one can think of as a localized momentary increase in temperature. It is only momentary because when the IR is re-emitted by the GHG, then KE decreases, and so there is no net increase in KE. The increase in atmospheric temperature that we call global warming comes from the earth retaining more energy to increase IR output in an "effort" to reestablish the equilibrium that has been lost by increasing atmospheric GHGs. As the earth retains more of the sun's energy, much of that is transferred as heat to the atmosphere, and so the atmosphere increases in temperature. I think I have addressed all your questions, but if not let me know.
I can't thank you enough for this. Im an environmental science student and am trying to better my fundamental understanding of the entire process or concept of global warming -> thus climate change, in general and this is so ridiculously informative, you have no idea how valuable it is.
A nice synthesis of the major scientific findings regarding the connection between increased greenhouse gases and the warming of the earth. Very interesting, well done, and thanks for making this.
Sir please upload more video on chemistry. Your ability to explain is top class, You can explain the concepts of each topic in a very good way and I can understand your every words. The way you lesson us ,I love this way . Your #stoichiometry video and #polar and #nonpolar videos was my life changing video . Sir make more video please please please please 🙏 🙏
Two comments - 1) All objects above 0K emit heat energy. What matters is NET heat transfer. Heat energy can flow from cold object to a warm object, more flows in the other direction. 2) Melting sea ice does not contribute to sea level rise. Melting ice sheets do contribute to sea level rise. Melting sea ice does change albedo, another feedback. Otherwise a great video.
What about all the interemed stored infrared energie in buildings masses and dark surfaces like streets wich leads to higher temperatures in urban areas?
Great question! Generally, urban heat islands cause a localized increase in temperature, for a variety of reasons, including what you mentioned, but also through increased concentrated human activity of all kinds. This can have different effects on the environment, but mostly is confined to affecting local weather patterns while having little effect on climate patterns. However the significance of its effect on warming the planet certainly is increasing the longer these heat islands exist, and they are getting larger and more prevalent. Some urban heat island are believed to have a larger impact on climate depending on location. For example large urban areas along the US Atlantic coast are thought to be contributing to changes in the Gulf Stream. The infrared you specifically asked about is only infrared as released energy, not as stored energy, although it likely would have originally been absorbed as IR, and then stored as an increase in kinetic energy. Once IR is released, it becomes part of the general effect of released IR from the entire earth's surface. So it is likely that the heat island affecting local weather has a far greater effect than heat island released IR has on the climate.
I appreciate it that you listed the correct order of ghg potency. This is so misquoted by the press & even lots of textbooks. I go around writing publishers to correct this be/c many of them are trying to promote 1 narrative. Just today an article claimed CH4 was dominant over CO2.
@@kimlibera663 Following your (or Salbys?) 'logic', CH4 would have no greenhouse effect at all since it has no permanent dipole moment. In short: It's nonsense.
Really great !! The most comprehensive video I have seen on the GHG effect, with all the physical phenomenons detailed, even calculations (how we know that -18°C would be Earth temperature witout any GHG). Thanks ! The only missing point probably being why high altitude atmosphere temperature decreases (as this phenomenon precisely invalidates the assumption that sun variability would be responsible of the current warming).
Two things-- 1) almost zero sun energy is absorbed by the troposphere. It is the earth's surface where absorption of sun energy takes place, and it is the IR energy released at the earth's surface which interacts with atmospheric GHGs. 2) The temperature of the troposphere (lower ~12,000 Km) decreases with higher altitude due to adiabatic expansion of atmospheric gases. If you have ever felt a can of compressed gas getting colder as you release the gas, this is the exact same mechanism. Adiabatic expansion refers to the expanding gases (atmospheric gases expand and decrease density as altitude increases) doing work on their surroundings, which is a different mechanism of energy transfer than conduction. The result is a loss of KE, which is a lowering of temperature. Beyond the troposphere, which is the stratosphere and beyond, the atmosphere does increase in temperature due to a few factors, including some interaction with sun energy. However the vast majority of GHGs stay below the stratosphere and so stratospheric GHGs have little effect on warming.
Great video. How long will it take for the world to rebalance to 255K? Just a IN=ACCUM unsteady state diff eq for MCpdT/dt of the air? And water and land?
Great video. Very good explanation. However, I wonder how the Schwarzschild’s curve is considered in this model and what its influence in the calculation of the increased temperature. I know that’s an extra level of complication in the modeling, but it seems to be a critical one.
If you mean the Schwarzschild Equation I have not seen any application of it to global warming, but it seems like it would be relevant. Not familiar territory to me.
I have a small point, but I think a critical one to raise. You use the example of it taking 2,267 joules/gram to evaporate water then show how that energy is transferred into the atmosphere. But you didn’t mention the energy balancing which would mean 2,267 joules is lost from the surface for each gram of liquid H2O to be evaporated. This could lead to some concluding that the energy at the surface is not effected by this transfer of energy of evaporating water. Thank you for the video.
Great point. Assuming a steady GHG concentration in the atmosphere, there is negligible kinetic energy change at the surface due to evaporation because of surface water absorbing sun energy or conductive transfer if the air is warmer. So rather than cooling, evaporation would instead likely reduce the amount of heating at the surface, attempting to approach an equilibrium. But since increasing atmospheric GHGs disrupts the earth's entire energy equilibrium, the net result of water surface energy absorption is greater than the amount lost through evaporation, which is the mechanism through which the earth's equilibrium is re-established-- that is, increasing the earth's surface temperature (heating), which includes heating surface water. So now we have greater evaporation, but again, that would serve to reduce the magnitude of the temperature increase (heating) from absorbed solar energy, rather than cooling. Hope that makes sense!
@@CrashChemistryAcademy I am not sure that helps. Perhaps I worded the question incorrectly. At the moment a gram water is evaporated, the surface loses 2,267 joules, which is now 2,267 joules in the atmosphere, correct? Granted, if it is daytime, the surface will continue to absorb energy. The way you worded your reply it appears you are claiming the surface never loses energy. If this were correct, we wouldn’t be talking, we would have died long ago due to a runaway condition. And this is the point I was trying to address. The surface energy reduces 2,267 joules per gram of H20 evaporation, that 2,267 joules then is transferred into the atmosphere, correct?
Yes, that is correct. However the transfer of the 2,267 joules to the atmosphere occurs as potential energy. Surface water gathers kinetic energy via radiant heat (sun) or conduction from a warmer atmosphere (sorry I left that out in first answer), both of which increase the KE of water molecules. If a surface molecule has enough KE to be able to overcome its attraction to the surrounding water molecules, it will break free and go into the gas phase. This constitutes a positional change in the water molecule, and at that point the increase in KE used to break attractive forces becomes potential energy. So the 2,267 joule increase in the gram of water is potential energy and does not contribute to atmospheric temperature. The significance of the increase in water vapor is a change in precipitation patterns, in particular larger amounts of rain water during precipitation; also changes in storm patterns, changes in cloud formation, wind patterns, and more energy in precipitation events like storms and hurricanes.
For the first time of my educational life I have seen such kind of video. Where you have showed how global warming is developed collaborating with thermal physics.Thanks a lot of Sir. ❤❤❤❤❤❤❤
1) Is the energy received from Sun used in Earths different "spheres"? 2) Stefan-Bolztman equation relates T^4 to the heat energy balance Sun Earth. How does T relate to the surface temperature of the Earth? If T is certain value what does it mean really in terms of the dynamically varying temperatures in the different "Spheres" of Earth? 3) How can you prove that the CO2 difference from 1870 to now is only from human sources? It is well known that in previous geological times CO2 was much higher than today and there was NO industry burning FF back then.
For your first two question, can you clarify what you mean by the earth's "spheres"? I'm not sure what you mean. For Q3, there is a fair amount of concrete evidence that the increase in CO2 of the last 150 is from human activity. The most compelling I think is from isotopic analysis. Please see this video for an explanation-- ruclips.net/video/b4QDokHJFIg/видео.html "Evidence for Human Generated Increases in Atmospheric Carbon Dioxide." Further, the carbon cycle is influenced by a great many geologic factors, and the geology of the earth changes quite a bit over geologic time periods, and so the amount of atmospheric CO2 changes as well, so CO2 naturally fluctuates over long geologic time periods. 150 years is a blip geologically-- it should have little significance in a geologic perspective, however CO2 concentration has changed dramatically in that geologic blip. That alone is a strong indication that this change in CO2 is not caused by natural phenomena.
Using Stefan-Boltzman in equilibrium, CO2, being 0.04% of the atmosphere, contributes little to the total Earth emissivity of about 0.95. CO2 alone doesn't give a warming result. Estimates of atmospheric H2O are all < 5% but even if atmospheric H20 were to double to 10%, Stefan-Boltzman gives the new equilibrium temperate increase at < 1C. Is that correct?
The fact that emissivity of CO2 is so close to 1 at relevant IR ranges supports its importance in radiative forcing as described in the video, and so supports its importance to warming. Atmospheric water vapor concentration is limited by the amount of liquid water (primarily in clouds and surface water) that enables condensing vapor to reach an equilibrium with evaporating liquid water, which is what we call 100% humidity. This equilibrium can get as high as 4% atmospheric water vapor in hot climates. If water reached 10% of atmospheric gases, that would likely be past water's tipping point and so the earth would be in a runaway warming, so likely no equilibrium would be reached, at least not before we are all dead. Quantifying emissivity will give the same warming values presented in the video.
There is no mention of the radiative scattering and formation mechanisms of cloud. It is the most essential mechanism of the energy exchange between the atmosphere and the deep space.
Radiative scattering from clouds is termed albedo. Albedo is mentioned a few times in the video. Cloud formation itself is certainly important to warming, but the complexity of cloud formation warrants a separate video.
@@CrashChemistryAcademy The concept of albedo applies to all objects not just clouds. You did mention this concept. I am specifically referring to the radiative scattering and formation mechanism of clouds this video does not mention. The albedo of a cloud is integrated from the scattering cross section derived from those mechanisms. These mechanisms are the most essential for computing the overall albedo of the earth. However these mechanisms are extremely complex, chaotic and largely unknown.
The cooling occurs due to a process called adiabatic expansion of gases. The upward expansion of atmospheric gases due to KE and gravity does work on the surroundings and so loses KE, which results in cooling. It is this cooling that reduces the energy of infrared loss to space, disrupting the earth's energy equilibrium, and so the earth retains more solar energy, which warms the earth, in order to get that cooled atmosphere to a temperature that restores the equilibrium. That cooler atmosphere is the basis for the earth's warming.
In this argument, it's also crucial that the atmospheric lapse rate is not itself affected by changes in the greenhouse gas concentration. Otherwise it wouldn't be possible to work our way down from the emission layer to the ground using a temperature curve of the same slope for all CO2 concentrations. This is indeed a good approximation because the lapse rate is determined by the majority gases (oxygen, nitrogen), not the trace gases.
Yes, this happens quite a bit-- KE transfer through conservation of momentum, called conduction. The issue is does that increased KE stay in the atmosphere as KE, which would increase atmospheric temperature. The answer is only momentarily, the reason being that eventually that KE transfer would come to to another CO2 molecule, which would then lose that energy via release of infrared, which means that energy as KE is now lost. This is covered in 24:45 to 25:57 in the video.
@@CrashChemistryAcademy.So you state "and here i would like to address a common misconception which is that carbon dioxide absorbing infrared energy directly increases atmospheric temperature that is not the case 25:10 any change in kinetic energy is momentary ..." but Why? Why would that KE be transferred to a CO2 molecule when there are thousands of N2 and O2 between it and the next CO2 molecule?
Yes, a good idea to look at the numbers-- For every 1,000,000 air molecules, there are (approximately) 420 CO2 molecules and 990,000 N2 and O2 molecules (combined). The 420 CO2 molecules is up from 400 in 2020 and 280 at around 1850 and before. To simplify, let's just say there are 4 CO2 molecules for every 10,000 air molecules. If in fact the increased KE of 4 CO2 molecules transferred and spread through those 10,000 air molecules, the overall increase in temp is likely too small to be measured. However there are two mitigating factors: 1) the majority of CO2 molecules absorbing IR will then emit that IR before colliding with another molecule, so no overall transfer of KE. 2) Eventually, for those CO2 molecules that do transfer KE through conduction, because the CO2 is so thoroughly mixed within those 10,000 molecules, and at standard conditions a gas particle experiences about 10^10 collisions per second, CO2 will pick up that energy again over a very short time period and release it as IR. CO2 continuously emits IR simply due to its temperature, and if its KE is raised a bit, that just means the IR it emits will have a higher energy. Regarding gas expansion: again, any expansion would be negligible due to there being such a proportionately small energy increase in a large amount of air molecules, but even more important, and more interestingly, that expansion would be adiabatic, and result in a loss of KE. Adiabatic expansion occurs when the expanding gas does work on the gas it is expanding into, and the result is a loss of KE, which means the expanding gas's temperature would decrease. Adiabatic expansion is why the troposphere gets colder as altitude increases. Lastly, regarding expanding gases rising-- it is the conduction from a warm surface of the earth to cooler air molecules at the surface that results in an expanding warm mass of air, which will then rise. This is convection. Convection is a far more powerful mechanism for transferring heat than conduction, and it is convection currents that account for much of the weather and the climate that we experience.
Very cool video, I covered this only in year 10, in IGCSEs chemistry in very little detail. This was interesting for going so much in depth, so thank you! Unfortunately the world is only money oriented... I don't think people understand that it's not the only problem, we are destroying the world in so many ways, and no solution is going to allow us to live with the same quality of life we have now, we are polluting too much, and the disparity is too great... So much for we're all equal...
Same quality of life? I'd be interested to know how you rate the quality of life before the industrial age. I hate pollution too, but come on. Also, how was that air quality in London in the 18th century when everyone was burning wood and coal to stay warm? Or how about present day Saharan Africa where they cook over fires fueled with dung? Imagine how drastically their life would improve with a couple coal or oil-fired powerplants.
@@Tommy-my1jw So massive worldwide heat waves, out of control fires, and flooding is a lot better alternative. I certainly agree with you! Thanks for making this important point.
@@bubbahotep6316 those are the realities of living on a planet differentially heated by the sun--along with countless other drivers (including C02). It's unfortunate we've been coached into believing that we can do something about it. I'm all for reducing our so-called carbon footprint, including reducing pollution overall. I just have no expectation whatsoever that our climate will be appreciably affected.
How about the radiation that is NOT absorbed by CO2 and other greenhouse gasses? Won't they escape from the land/sea surface and thus lose more heat. Is that proportion negligent ie. doesn't change the big picture? Or is there a mechanism that blocks that IR radiation, too?
There are windows, gaps in the absorption spectrum of the whole of greenhouse gasses, in which emitted IR goes directly to space. These gaps are significant in that the warming of the earth would be greater if those gaps did not exist, meaning all IR frequencies were absorbed by GHGs. The gaps in IR frequencies, the IR that is not absorbed, are small compared to the range of emitted IR frequencies that are absorbed by GHGs.
If the Earth rebalances to 255K at a higher altitude, why would it be dimmer at a higher altitude than at a slightly lower altitudue? Is albedo a function of altitude?
The amount of energy per emitted photon decreases as the temperature of the emitting material decreases. So at the colder temps of higher altitude, less total IR energy is released per unit time than at the warmer earth's surface.
Albedo is the reflectivity of the earth itself. The entire earth reflects sunlight (otherwise it would be invisible), and so that is the earth's albedo. With an atmosphere, the albedo increases due mostly to clouds, however now we can more significantly include particulates as contributing to albedo due to the consistent wildfires occurring around the globe. So without the atmosphere, the albedo would be less than 0.3. With the atmosphere, it is hovering around 0.3.
Hi and thanks for this great video! One thing I still can't get my head around: The rise of atmospheric temperature is from air heated at the earth surface and then moving up (convection)? This process is increased because earth "needs" a higher temperature now that the increased greenhouse gases forces the IR-escape to a higher (and therefore colder) point. Okay, but what is the mechanism by which this "need" is articulated? I guess the same amount of air is heated at earth surface with or without higher amount of CO2. What would have happened with this air in pre-industrial times? It would have risen and then been transferred by conduction of kinetic energy in to CO2 at the original lower height and got "vented out" there?
Yes, I regret that lack of clarity. The energy ultimately comes from the sun. If you think of the earth system (by which I mean the earth + its atmosphere) in space as a system constantly receiving and emitting energy, that incoming versus outgoing energy has to reach a balance (equilibrium) simply due to the fact that if it did not, lets say in the case of emitting less energy than received, then the earth system would continue to heat up infinitely, which cannot happen. Conversely, if the earth system emitted more energy than received, then the earth system would continue getting colder until it reached absolute zero, which violates the 3rd law of thermodynamics. The happy medium here is of course the earth system, if not already at an energy equilibrium, will always go toward that equilibrium by emitting less energy or more, depending on which direction will get it to that equilibrium. The atmosphere is not heated by the sun. Nitrogen and oxygen do not absorb EM energy in the range emitted by the sun. There is a small amount of sun-emitted IR that is absorbed by atmospheric GHGs, but that gets re-emitted and does not affect temperature. It is the earth's surface that absorbs the sun's energy, which can then get transferred to the atmosphere via conduction. With higher amounts of CO2, more air is heated via conduction as the mechanism of maintaining the equilibrium, and this is how the earth system is obeying the laws of thermodynamics.
@@CrashChemistryAcademy thanks alot for the reply! I get the concept of the incoming and outgoing energy being in balance, but I'm still wondering about what mechanism, what kind of energy transfer, that makes the energy that leaves the surface though convection later leave the atmosphere and go out in space. It must be transfered from energy in the form of the moving gas, into long wave radiation, no? How?
GHGs are able to generate IR without first absorbing IR. It only depends on the temperature (KE) of the particle. Higher KE = higher energy photon, & vice versa. This is the basis for black body radiation. Any energy leaving the atmosphere does so via IR emission. So your last statement is correct.
Because the vast majority of IR released to space is released in the troposphere, the stratosphere has little impact on global warming as far as GHGs are concerned. The one major GHG in the stratosphere, ozone, primarily absorbs UV, and due to that the stratosphere is warmer than the troposphere, but that has little impact on tropospheric/global warming.
I would love a reference to the paper comparing potency of greenhouse gasses which concludes that methane and HFCs are less potent than CO2. Thanks for your video.
Thanks much for your question. In looking back at the video, I can see now that some of my statements were poorly considered. The question of CO2 versus CH4 & HFC’s (etc) radiative forcing is complex and I simplified far too much. I assume there are papers out there that support CO2 being more important than other GHGs, besides water, regarding overall radiative forcing, but my statement came from discussions with a couple of climate scientists, not published papers. I should have attempted to better explain the perspective I had (!) which is as follows: There are several points that need to be considered: 1) The usual comparison of CO2 and CH4 potency for radiative forcing are per unit mass, usually kg, which already skews the data, as follows: for every 1 kg of CO2 and 1 kg of CH4, there are 44/26 or 2.75 times more CH4 molecules than CO2 molecules. So the comparison is immediately skewed. (44 and 26 are the periodic table masses CO2 and CH4.) 2) It is true that in comparing kg to kg, methane (and HFCs, etc) are way more potent than CO2. However in practice, that particular factoid about kg CO2 vs kg CH4 doesn’t matter because CO2 has several orders of magnitude more kilograms in the atmosphere. So the kg-for-kg factoid leads the broader public to not worry enough about CO2 emissions versus public worry about CH4 emissions. We should worry about the overall potency (volume-to-volume x number of molecules per unit volume), not the kg-for-kg statistic. 3) The statistic generally arrived at on an internet search comparing the radiative forcing of the two gases is from EPA data that states CH4 is 25x more powerful than CO2. This is a tricky calculation, and is given per 100 years for a given equal mass of CO2 and CH4. A few complications-CH4 half life is ten years, CO2 half life is hundreds of years (could not pin that down, several reputable sources gave a large range); the time span of the calculation (100 years) is a huge consideration because of the large difference in half lives; the half life of CH4 is due to its oxidation into CO2, which adds a small (by comparison) amount of CO2 to the total; and finally, the calculation avoids the all-important consideration of actual amount of molecules of CO2 versus CH4 present in the atmosphere. 4) I think the reason the kg-for-kg factoid entered the discourse is that it is necessary to explain one thing - namely why methane leakage from the gas/oil industry is so much worse than just combusting it into CO2. If methane and CO2 were equally "potent" on a molecule-for-molecule basis, then methane leaks from, e.g., natural gas pipelines, wouldn't matter for climate change. But leaks do matter, because a mole of (uncombusted) methane creates far more radiative forcing than a mole of CO2. 5) This 2016 data is from the site ourworldindata.org/greenhouse-gas-emissions#annual-greenhouse-gas-emissions-how-much-do-we-emit-each-year: In terms of CO2 equivalents (CO2eq) (GHGs are converted to CO2eq by multiplying each gas by its 100 year 'global warming potential' value: the amount of warming 1 ton of the gas would create relative to one ton of CO2 over a 100 yr time scale): CO2 74.4%, CH4 17.3%, and HFCs 2.1%. This is what I was getting at in the video without explanation, except there is a much larger difference than indicated here, since, again, the comparison here is between masses rather than actual numbers of molecules (per given volume of air), the latter giving the real result in terms of comparing radiative forcing. Thanks for bringing up this question. I’ll have to edit out some of those statements, as they are misleading in terms of how they are phrased in the video. (RUclips hugely restricts editing of a published video, I’ll give it a try.)
@@CrashChemistryAcademy Thank you for your thorough response. I was particularly interested in this question because of the trickiness in calculating potency of methane and carbon dioxide. www.nature.com/articles/s41612-018-0026-8 and eprints.whiterose.ac.uk/108770/1/SLCP_INDC_withfigs.pdf are two good papers on this topic - they compare using GWP100, GWP*, and GTP for estimating what we are calling potency. I understand now that you meant to say that CO2 is a bigger problem in our atmosphere now. Based on point 4) it sounds like you agree that one kilogram of avoided methane is more significant than one kilogram of avoided carbon dioxide. Ultimately, this is what I was wondering. I appreciate your input.
(Belated reply due to youtube diverting any comment with a link from the usual panel of comments). Anyway... Thanks so much for the references, very interesting/enlightening. A complex issue to be sure.
Spectacular video and wonderful comment/conversation here. I caught that statement (CH4 vs CO2 global warming potential, and relative impact) too, but I was so happy to see this comment exchange. I watched a mythbusters video on GHG’s impact on temperature, and an IPCC video on global warming data, and the comments section was pretty brutal. I hope everyone there makes it to this video. Thanks for taking the time to condense the basics of an earth systems science course into 45min. Well done explaining the math and physics.
Really great explanation! I have a question about the albedo. How much does cloud cover affect the albedo? Since clouds appear white I'm assuming they reflect light similarly to the north and south poles( or is that a misconception?). And Since global warming leads to more water vapor in the athmosphere, does this atleast have the effect of more clouds reflecting more sun light and slowing the feedback loop you describe at the 37:20?
My understanding is (this is not an area I am very familiar with) that higher average temperatures do in fact affect cloud formation, but I believe it affects more where clouds form rather than how much clouds form. It certainly seems like there should be a correlation between increased water vapor and increased cloud formation, but I do not know if that is the case. Keep in mind that many areas of the earth are become dryer due to higher global temperatures, which reduces average moisture in the air. And yes, more cloud formation would increase albedo. An interesting side note is that there are people in the "geoengineering" biz that have been coming up with ways of increasing cloud reflectivity (thus increasing albedo) in various ways through chemical manipulation. For a long time these ideas have been marginalized, but those ideas are becoming more prominent as our earth hurtles toward a 2 C global increase.
Albedo is only a function of reflectivity, and that can and does happen anywhere on earth and in the atmosphere. A sizable amount of the albedo is produced by clouds, which are constantly moving. The fact that earth can be seen from space is due to reflected light, which is part of the albedo, and yes it depends on what kind of surface is reflecting the light--darker surfaces = less albedo than lighter surfaces. Albedo is constantly fluctuating, but has stayed at a relatively constant average value over the last several thousand years, around 30%, until recent warming began to melt ice sheets, which reflect a lot of light, and so less ice = less albedo (liquid water is quite a bit darker than ice).
Hydrogen has had a difficult time getting to mass marketed cars for a few reasons. One significant problem is the manufacture of hydrogen gas requires a great deal of energy. Until that can be made more efficient, there is little incentive to use it to reduce greenhouse gas emissions, unless completely green energy is used in the process of hydrogen manufacture, but there are much smaller sources of green energy right now on the planet compared to fossil fuel use. Note that the same source-of-energy problem exists with the energy used to make electric cars, including making batteries AND recharging those batteries. Another problem for hydrogen is storage since it is a gas, as well as storing it safely since it can be explosive, far more explosive than gasoline. Then there is the culture of industry. Industrial decisions have a great impact on the use of various technologies, and the car industry has decided to put their R&D$$ into electric cars rather than hydrogen cars.
your video explains where where i had difficulty understanding. the altitude upwards radiation to space begins is where it's blackbody radiation temp. 5.4km above is middle of troposphea where conduction and convection still occures. wouldn't it complicate the model?
Yes! I've tried to present a model that is fairly accessible. There are far more details, including what you mention, that climate scientists account for. There are a great deal of variables to consider, and I believe I covered those that impact warming the most.
Are the relative intensities of sun and Earth emission spectrums to scale to each other? I get a sun max of 411 at 0.495 microns (yellow) and a max of 25 at 10 microns for Earth.
They are not to scale relative to each other (the y axis says relative intensities). I did not want to make the scales equal since the earth's curve would have been fairly flat compared to the sun's curve, which would have obscured the intention of the graph.
Thanks for all the work put into this video. In the end, adding the prediction of devastating consequences from global warming is not helpful. There are other points of view and scientific research that suggest different outcomes and predictions of the earths future climate.
Water vapor in the earth's atmosphere varies between close to zero % to 4% depending on conditions. CO2 percent around the globe is now about 0.042%, up from 0.028 % around 1850. The added water vapor is far smaller than the water vapor already in the air, and has little discernable impact. Since the percent of CO2 in the air is so small, added CO2 from burning fossil fuels is very significant.
Yes, and that is exactly how black body radiation works. It is just the moving nuclei in atoms at the surface of a body generating EM waves. GHGs will always be emitting electromagnetic radiation due to the vibrations of their nuclei. The amount of vibration dictates the energy of the emitted radiation. Since we measure that vibration as temperature, higher temperature particles emit higher energy radiation than lower temperature particles. Everything in the universe that has charge is constantly emitting EM waves that are proportional to their temperature.
When comparing equal numbers of particles per unit volume, carbon dioxide produces a larger radiative forcing than any other greenhouse gas except water vapor. Water vapor is discussed in detail in the video, in particular beginning at 35:20, including its own feedback effect as well as the feedback of CO2 on water vapor levels.
Thanks for you thoughts. How do you know that balance is a good thing for humans? Why dose photosynthesis not enter your equation? Why don't you mention the little ice age ending at the start of your diagrams.l/charts? How do calculate the amount of co2 naturally produced by the planet?eg volcanically etc? Why do you think only planet earth is warming an the rest of the solar system is in balance ? I have many more questions but heres a start. Again thank you for your theory.
The balance allows for a stable climate. Without that balance, extreme climate events begin to happen, such as more extreme hurricanes & tornadoes, more extreme droughts, more extreme flooding, generally more severe weather around the entire earth. By photosynthesis I assume you mean CO2 fixation. Yes plants remove CO2 from the atmosphere, but plants also produce CO2 via cellular respiration. It certainly would be better to have more plants, but it will not fix the excess CO2 pouring into the atmosphere. Ice ages and geologic events take place over many thousands to millions of years. Anthropogenic global warming has occurred in 150 years. It would not be possible for the earth's geological events to produce nearly this amount of change in such a short time span. CO2 production can be determined through the earth's carbon cycle. For the question of balance on other planets, they may or may not be in balance. If not they can be getting colder or warmer. Venus has had runaway warming but I believe that has reached an equilibrium, but I don't really know.
@@CrashChemistryAcademy Thank you very much for your reply and time. I just need to understand. Why do you think atmosphere can be balanced? Nature is extreme and balanced. Records only go back to 18/19 century before that global measurement were not possible. 1850 was the end of the little ice age. Plant respiration removes half of its co2 intake at night, not to mention the dramatic growth extra co2 intake causes. When you say human causes in last 150 years are you referring to the missing fusion reactor of Fukushima? The microwave technology governments use for weather manipulation , Or 3/4/5G communications or what? I really don't understand what you mean to achieve other than inventing a tax on air. (Water taxes are crazy enough). All planets in solar system are heating so it's not just co2 causing earth to heat. I enjoyed your upload I think there's a lot more to the story though, many variables. I think this is all just another distraction by the powers that be, honestly. My best wishes to you, thank youand respect.
You forgot the clouds. 2016 I noticed more clouds -> colder weather. NOAA measured the temperature over sea and land and also notices a cooling trend from 2016. Our solar panel data show me what is the thermostat - The Sun (controlling the clouds).
Although if you were thinking purely in terms of the range of EM radiation put out by the sun, by far the majority is IR, but compared to both visible and UV, IR has far far less of both photons per unit time and total energy per unit time.
@@CrashChemistryAcademy thanks. If I take a 5800K blackbody curve and scale it by Earth-sun distance compared to total output from a sun sphere, I get about 70 W/m2 when I integrate from 1-100 microns. What else needs adjusted for it to be around 1%?
CO2 is not really thought of as something that stores heat, due to it being a gas and have a very low heat capacity. Rather it absorbs heat in the form of infrared radiation, but it then also releases heat as IR.
Great video! Now, if you can scale this down to what a 7th grader could understand. Do that and your average American will stand a chance of comprehending.
An interesting comment. My motivation for making this was to go beyond the far too many 7th grade-level global warming/climate change videos out there and try to convey some of the real science involved. I made it for my high school physics students, who have also taken chemistry. If you have any questions about the material I would be happy to clarify.
How do you explain that co2 levels were 1000 ppm millions years ago and that situation didnt produce an increase in temperature, but the opposite, a decrease ? This explanation does not explain the Evolution of the earth climate in the past. The climate system is highly stable and this explanation requieres a CO2 concentration almost constant to avoid a very unstable system.
Climate is not stable over geologic time periods, and fluctuations in CO2 are a large part of those climate changes. However, we have had large climate change in the past 150 years, a degree of change that is far beyond the earth's ability to cause change in geologic time. 150 years is an insignificant amount of time in the geological record, and so having such a large change in such an extremely short time span indicates forces at work that are not of the earth's doing.
We have had a very stable climate in the recent past. Changes of 1 degree in a century are not inusual. Looking at geological records we can see greater increases and decreases in temperatura without human intervention. This climate theory centered un co2 is uncompleted and innacurate
We know that the temperature throughout the earth's history has fluctuated quite dramatically, far more than what we are experiencing now. However those fluctuations occur over thousands to millions of years. Our current rise in temperature has only been in last 100 years, which is unprecedented in the earth's history. Further, the temperature of the last 8000 years, the dawn of modern humans, has remained stable, and so our civilization has evolved at a time where the global average has been around 14.5 C. This also correlates to a fairly steady 280 ppm CO2 in the air. So we are used to evolving and living in a climate that has those data points. The earth will survive an increase in temperature, the question is what will happen to its inhabitants? How will they adapt? Will it be easy, hard, catastrophic? Our current course suggests we are headed into a dystopia of the type popular in current fiction and movies, not a great scenario.
@@CrashChemistryAcademy Sorry for being unclear. Since I am not a paying member, i can't download the video. Would you be willing to send it to me via email ?
There is no youtube service that allows you to download content, due to violation of copyright law. Can you tell me why you need the video file? Please reply to joelwax3@gmail.com
All radiation is forms of energy. The radiation that the video is concerned with is called electromagnetic radiation, which (in the video) includes infrared, visible, and ultraviolet radiation.
This is such a great and clear explanation! It is very important to be informed about this topic, since it concerns us all. The only question I have left from the video is why is it said then that CH4 is a more potent greenhouse gas than CO2?
Thanks much for your question. In looking back at the video, I can see now that some of my statements regarding CO2 vs CH4 needed clarification. The question of CO2 versus CH4 & HFC’s (etc) radiative forcing is complex and I needed to better explain that (!) as follows:
There are several points that need to be considered:
1) The usual comparison of CO2 and CH4 potency for radiative forcing is per unit mass, usually kg, which already skews the data, as follows: for every 1 kg of CO2 and 1 kg of CH4, there are 44/16 or 2.75 times more CH4 molecules than CO2 molecules per unit mass. So using mass immediately skews the comparison due to it not being an equal amount of CH4 and CO2 molecules. (44 and 16 are the periodic table masses CO2 and CH4.)
2) It is true that in comparing kg to kg, methane (and HFCs, etc) are way more potent than CO2. However in practice, that particular factoid about kg CO2 vs kg CH4 doesn’t matter because CO2 has several orders of magnitude more kilograms in the atmosphere. So the kg-for-kg factoid leads the broader public to not worry enough about CO2 emissions versus public worry about CH4 emissions. We should worry about the overall potency (volume-to-volume x number of molecules per unit volume), not the kg-for-kg statistic.
3) The statistic generally arrived at on an internet search comparing the radiative forcing of the two gases is from EPA data that states CH4 is 25x more powerful than CO2. This is a tricky calculation, and is given per 100 years for a given equal mass of CO2 and CH4. A few complications-CH4 half life is ten years, CO2 half life is hundreds of years (could not pin that down, several reputable sources gave a large range); the time span of the calculation (100 years) is a huge consideration because of the large difference in half lives; the half life of CH4 is due to its oxidation into CO2, which adds a small (by comparison) amount of CO2 to the total; and finally, the calculation avoids the all-important consideration of actual amount of molecules of CO2 versus CH4 present in the atmosphere.
4) I think the reason the kg-for-kg factoid entered the discourse is that it is necessary to explain one thing - namely why methane leakage from the gas/oil industry is so much worse than just combusting it into CO2. If methane and CO2 were equally "potent" on a molecule-for-molecule basis, then methane leaks from, e.g., natural gas pipelines, wouldn't matter for climate change. But leaks do matter, because a mole of (uncombusted) methane creates far more radiative forcing than a mole of CO2.
5) This 2016 data is from the site ourworldindata.org/greenhouse-gas-emissions#annual-greenhouse-gas-emissions-how-much-do-we-emit-each-year: In terms of CO2 equivalents (CO2eq) (GHGs are converted to CO2eq by multiplying each gas by its 100 year 'global warming potential' value: the amount of warming 1 ton of the gas would create relative to one ton of CO2 over a 100 yr time scale):
CO2 74.4%, CH4 17.3%, and HFCs 2.1%. This is what I was getting at in the video without explanation, except there is a much larger difference than indicated here, since, again, the comparison here is between masses rather than actual numbers of molecules (per given volume of air), the latter giving the real result in terms of comparing radiative forcing.
Thanks for bringing up this question. I’ll have to edit out some of those statements, as they are misleading in terms of how they are phrased in the video. (RUclips hugely restricts editing of a published video, I’ll give it a try.)
@@CrashChemistryAcademy I'm sorry I have just now seen your response. Thank you so much for such a dedicated and clear explanation!
@@CrashChemistryAcademy Thanks for that. These are issues I certainly would not have considered because no one seems to talk about it! Your explanation of mass:mass versus molecule:molecule considerations, and that of half life significance, is especially appreciated (and interesting).
Thank you for this clear explanation. As a physicist, I have never understood why people with little or no understanding of the basic physics of the process should have such strong opinions about it, and why we, as a country, empower such ignorance and allow it to deter us from necessary action. This extreme arrogance based on ignorance may will impoverish our grandchildren.
I don't know. There almost seems to be a cult of self-righteousness taking over-- people love that heady sense of knowing they're right and you're wrong, and what you have to say is irrelevant. It's a weak position from which to hold a conversation or to learn about what is going on in the world.
I periodically come back to this lecture as I make my way through an environmental science degree and it never disappoints.
Thanks so much for a very gratifying comment. You should know (if you haven’t already noticed) that I pinned a previous comment and my answer regarding the potency of CO2 versus CH4, something that was not well considered in the video narrative.
The best, detailed video on how and why CO2 causes global warming I've seen to date. There is sooo much misinformation and misinterpretation of how CO2 causes climate change out there and refutations based on those strawmans, its painful. Thank you for this.
You'welcome, thanks for the comment!
If I could give this two thumbs up, I would. Wow!
This is absolutely phenomenal, I mean of course not the condition of the world but the video. This is such a clear explanation of the science behind global warming without making a person have to research on 50 something websites for the same information. And the clarity with which it has been explained is something I cannot put into words. Thanks a ton!!
Thanks! I appreciate the comment!
Super underrated video! If only people could dedicate 45 mins of active listening to watch this video (especially the extremists on both ends of the global warming spectrum), we could eliminate most of these polarizing arguments, most of which do not even mention the science. This is one of the reasons why I love STEM: it provides ground truth within a sea of lies and misconceptions.
Amen. Hope this gets some traction. Thanks for the comment.
@@miked5106 come again? So the initial 97% doesn't drive catastrophic warming, but the residual 3% does?
I had some ideas of how global warming occurred but this presentation hugely clarified everything I was trying to understand, as well as going far beyond what was, for me, the basics of how all this works. Thanks so much for posting this. It is essential for the entire world.
Videos like this are so incredibly important. Thanks for posting this-- I had no luck finding anything about the greenhouse mechanism other than difficult science or dumbed down videos (all basically just saying that greenhouse gases act to put IR energy back into the earth, i.e., the usual "greenhouse gases act like a blanket" and nothing else). This was most edifying and exactly at the right level for anyone who wants to get to an accessible depth with this. Again, so important to bring this information to a general audience.
Great video. As good as it is, I have to say it sets my teeth on edge hearing anyone say "a warmer atmosphere holds more water vapor" since this is a complete misrepresentation. It really sticks out in this video, which is so thorough otherwise and not trying to be too simplified. How do you know that "a warmer atmosphere holds more water vapor" is false? Because you'd get the same increase of water vapor with temperature even if there were no oxygen or nitrogen or any other atmospheric gases available to "hold" the water vapor.
I guess I'm not quite following. Are you saying if the atmosphere were made of different gases that it would still be able to increase maximum water vapor at higher temps? Or did I not get that right? At any rate, our atmosphere, at 25C and 100 % humidity (maximum possible water vapor), will have 30 molecules of water per 1000 molecules of atmospheric gases. At around the temperatures that the earth maxes out at, perhaps 40C, the maximum water molecules (100% humidity) goes up to about 40. Below 0C the maximum amount of water vapor (100% humidity) goes to below 1 molecule per 1000. I'm not sure how the word "hold" misrepresents that.
@@CrashChemistryAcademy Thanks for the quick reply. In the spirit of citing original sources, try googling "Alistair B. Fraser penn state bad meteorology" for a brief explanation (the first entry) and "water vapor myths Steven M. Babin" for a slightly more detailed one. I appreciate your taking the time to read this, I'm in the AGW field too and know how "interesting" some of the responses one gets can be. :)
Thanks so much! The Babin article was great-- it clarified the fuzziness I've had about the behavior of water vapor. I am not working in AGW, I am a high school chemistry teacher and made this video for my students. As a chemistry teacher this seems like something I should have known, or at least should have looked further into to alleviate my fuzziness, so thanks for the article! It is much appreciated. As for my statement in the video, I will let it stand since youtube has very few editing capabilities, as well as the significance that higher temperature can result in more water vapor being the salient point here.
Thanks for a concise explanation of global warming. It has been confusing for most.
Hombre! Hermano! Thanks for watching!
I am 13 years old and i am always learn from u!!!!
Thanks 😊
Most informative video on the internet considering circumstances.
Interesting but shows fundamentally wrong physics. There is no radiation transfer of heat in the athmosphere. It is only tranfered by convection in the high pressure at the surface. This means that the ammount of grean hous gasses have no impact of the surface temperature. The difference of temperature is related to the sunlight thats reaches the surface. As the difference in summer and winter far from the equator. The radiation is only valid in the stratosphere and higer altitudes. Also the mean temperature of the earth is derived form a flat surface whitch is not even close to the real shape of the earth.
This had been a good comment, one that seemed reasonable, until you stated that the earth is not flat. That is fundamentially incorrect, and really, when all is said and done, throws your entire argument into the toilet. You really had me going there.
@@shoppehow Thanks for a good chuckle. I could not imagine a better reply to this pseudo-science post. Kuddos to mr. shoppe.
Your problem is that a pirani guague proves that conduction dominates ir radiation on heat transfer by 249:1 at 1 atmosphere pressure. Here's another problem.actual greenhouses cool at night despite being transparent to incoming ir radiation therfore back radiation, if it exists, has no effect on the temperature of surface materials.
Wait till you learn about venus lmao
This video is very informative.
In addition to the higher emission altitude that averages about 5.5 km altitude (15km at 220 k for CO2, and 3.5km at 265 k for water vapor), the width of the absorption spectra also increases when the more insignificant 'outer edges' of these spectra becomes more significant with the a higher probability to absorb with more greenhouse gas molecules in the atmosphere.
This narrows the atmospheric window, so that a broader emission spectrum to space at low temperatures will occur as well as a broader absorption spectrum near the surface increases the amount of absorbed radiant energy emitted by the surface.
A very interesting and easy to understand video that is worth sharing.
Thanks much for an edifying comment!
@@grindupBaker You will be able to measure different widths and amplitudes of the atmospheric window depending on the height above the ground, but it is problematic to be able to know what you are measuring in this way. Since the greenhouse gases not only absorb IR radiation but also emit IR radiation (Because they have a temperature), a spectroscope will not only measure the radiation from the ground, but also from the atmosphere between the ground and the spectroscope.
For that reason, you will be able to see a somewhat uniform radiation spectrum close to the ground, while measurements made higher up, let's say 8 km, will give a radiation spectrum that clearly shows the absorption spectra of the various greenhouse gases. These become more visible because the temperature in the atmosphere at 8 km altitude is much lower than at the surface. And where the greenhouse gases absorb at the ground, they will emit radiation from a low temperature at an altitude of 8 km. This results in pits or dips in the spectrum - because gases with a low temperature emit little effect.
In contrast, the atmospheric window, the area of the spectrum where the atmosphere does not absorb anything (practically speaking), will be read with the same strength as the one you had measured near the surface.
With increasing amounts of greenhouse gases, the atmospheric window will narrow. Conceptually, and if we think that we are moving the thermal spectrum into the visible part of the spectrum, the atmospheric window will essentially be transparent to wavelengths in the green spectrum. The imaginary green color will be mixed with orange and cyan, and will not appear as a sharp and pure green color, but if you increase the amount of greenhouse gases so that the atmospheric window narrows, the green color will become clearer and clearer, but not weaker.
It does not become weaker because the surface which is now heated emits more power, and thus the power emitted through the atmospheric window must be distributed over a narrower spectrum. This increases the amplitude of the emission spectrum - which directly reflects the temperature rise on the surface.
The water in the sea does not have such an atmospheric window. In addition, heat flow in the sea takes place primarily through conduction, but also circulation.
But if you look at the thermal spectrum that the water surface emits, it will appear as an approximately black body where all wavelengths are somewhat evenly distributed in amplitude (within Planck's radiation curve). The emissivity of water is not 1, but around 0.95. So water deviates about 5% from being a black body in the thermal spectrum.
Wavelengths around 50 um have little effect at the temperatures we normally have on earth, and constitute only 2.7% of the effect emitted by 10 um (peak wavelength at 15°C).
Only 40TW of the heat energy from the Earth's interior reaches the surface. This corresponds to a flux of only 0.08W/m². At a surface temperature of 15°C (390 W/m²), the ground heat is responsible for only 0.014°C, and has no practical significance.
@@grindupBaker The emissivity varies a bit, ofcourse. Seawater and destilled water have different chemical properties, and also have different emissivity, but ball park figures is around 0,95-0,97. Also, the angle and the water temperature you measure have an impact on the emissivity.
Speaking of the energy balance, also have in mind that if a substance has an emissivity of 0.95, it also has an absorptivity of 0.95.
CO2 disolved in water do not contribute to any significant portion of what is emitted at 13-17 um. In this case, CO2 is a part of a fluid that already have a close approximity of a black body. In water, the molecules are tightly spaced. This allows the molecules to undergo quantum mechanical transitions way more often, and much more 'efficient' through collisions with each other than they do in a gas. This will broaden the absorption and emission spectra so much that the molecules absorb and emits almost like a black body.
Take a look at the emission spectra for liquid water and water vapor. They are quite different. While liquid water have an emission spectrum that is close to a Planck radiation curve, water vapor have more distinct emission spectra peaking at 72um and 6.8um (within the thermal spectrum).
@@grindupBaker Emission spectra and absorption spectra are the same, given the same substance in its current phase (solid, liquid, or gas), pressure and temperature.
If you haven't found emission spectra, you'll see them in the absorption spectra.
Learned a lot from your video, and liked your style of narration and how you kept ideas connected in a brilliant way.
Thanks!
Great vid, slow and steady with a logical flow of information. Best vid on this topic I've seen in terms of scope and depth.
I had not seen mention to heat island effect even though absorb emits IR energy , trees , green , white color roofs reduce CO2 IR land energy heat absorbing
This was briefly referred to a few times in the video, in particular as generalized albedo.
Fantastic video, sir. Very comprehensive and clear. Many thanks!
Thanks for watching!
A common criticism is that the effect of warming from CO2 decreases with a log relationship to concentration. Can you explain how this affects feedback and climate sensitivity?
Great question!
The physical chemistry of CO2 would not result in a decreasing radiative forcing (the imbalance between incoming and outgoing energy) by itself. However, one has to consider all the many variables present in the complex system of the earth-atmosphere, and the end result is an increase in the effect of CO2 on warming, not a decrease, as follows: Many of the variables involved here in the earth-atmosphere system can be summed up in the earth's carbon cycle. Before the 19th century, the concentration of CO2 remained fairly stable due to its involvement in the carbon cycle, and changes in the carbon cycle resulted in changes in CO2 concentration. As we increase CO2 concentration, the various carbon sinks that exist in the carbon cycle will remove much of that increasing CO2 (otherwise the current increase in CO2 concentration would be much more than what it now is). However, those carbon sinks have a limit, and so as we increase CO2 concentration those sinks begin to get less efficient, or more saturated, or however you want to think of it, and so the warming effect of adding CO2 increases as the carbon cycle gets less able to handle higher and higher CO2 concentrations, simply due to a higher rate of increase in atmospheric CO2. Once the carbon cycle is finally overwhelmed, which is called a tipping point, then we have a runaway greenhouse effect and the earth will boil away all its oceans. Although my guess is that the oceans will have already evaporated as we approach that tipping pint. This brings up the hydrologic (water) cycle, which again, will result in adding more water vapor (the most potent greenhouse gas) due to higher atmospheric temperatures caused by increasing CO2, and so this is one feedback that would also reach a tipping point.
Regarding climate sensitivity, I think this is where the idea of a decreasing log relationship that you mentioned comes from. Climate sensitivity as you may know measures the change in mean temperature due to a changing variable that produces radiative forcing, such as increasing CO2. But that measure has two distinct endpoints. The first endpoint is the change in mean temperature the moment that variable (I'll just call it CO2) reaches a particular change, such as doubling in concentration. The second endpoint occurs due to the fact that the moment the CO2 reaches that doubling (and stops increasing in concentration) is NOT the point at which the earth stops warming. Due to the earth requiring many decades to get back to the equilibrium of its energy balance to relieve that radiative forcing, the earth will continue to warm decades after the CO2 has reached its doubling. This rate of warming decreases logarithmically as the earth eases toward the reestablishment of its energy equilibrium. So that logarithmic relationship has likely been seized upon by climate change deniers, skeptics, etc., to say that the effect of warming from CO2 decreases with a log relationship to concentration, which is incorrect.
A simple analogy would be having a room at 10C with a water radiator in it. You turn on the boiler and set the thermostat to 20C. The boiler remains on until the thermostat reaches 20C, and then the boiler turns off (first endpoint is 20C). However the radiator will continue to release heat after the boiler turns off, resulting in a room temperature that is higher than 20C (second endpoint is >20C), until an equilibrium between the room temperature and the radiator temperature has been reached. (Note that 20C is not twice the temp as 10C, they are just two randomly chosen numbers.)
Hope that all makes sense!
@@CrashChemistryAcademy Thank you for your detailed reply.
@JJ well, thermal radiation transmission is not instantaneous, there are many lags due to its speed, its interception by CO2, the lag in CO2 re-emission, the equal chance of re-radiation of infrared either back to the earth or release to space, etc, and in particular the CO2-water vapor feedback takes a while to equilibrate. All of this spells a lag for re-establishment of thermal equilibrium in the earth-energy system.
Radiative forcing is only a measure of the difference in outgoing versus incoming energy, it is not a source of heat. It in fact can result in cooling, for example if albedo increases, then radiative forcing 'reverses', and the result is a decrease in temperature.
@JJ That seems to be correct. I guess I would like to clarify what is meant by thermal. The incoming and outgoing energies are electromagnetic radiation. They are only thermal insofar as they are able to interact with atoms and change their kinetic energy. Infrared leaving the earth is nothing more than infrared radiation. However when it is generated at the earth's surface by surface atoms' KE, that KE is reduced by the amount of energy contained in the IR photon. The IR photon itself is not heat. Likewise with sun energy. It is only thermal insofar as it is able to increase KE of earth's surface atoms that absorb it. This may be getting picky but I think it is important to distinguish electromagnetic radiation (which is not heat) from its effect on the objects it interacts with.
I think you miss a point about the minor greenhouse gases CH4 and N2O--they seem to be more powerful than CO2 because they absorb in what would otherwise be infrared windows, so they are less saturated than CO2 (I know CO2 isn't saturated at the edges of its absorption bands, but it is more so than the others).
Very clear video and Thank you very much from Thailand
สวัสดีประเทศไทย!
Informative, timely, and important video. Thank you for all the work you do to educate us about how the world works!
You're very welcome! Thanks for the comment!
@@joelweiner4156 Do you ever feel guilty propagandizing scientifically illiterate children with pseudo science designed and paid for by people who intend to frighten them into submission to a controlled economy wherein they will be exploited for the remainder of their lives?
Your explanations are deceptions; the insulation response of any material including "greenhouse gases" is logarithmic. The children you propagandize do not understand this concept but perhaps you too are just reading someone else's propaganda that you also have no ability to comprehend. At 400 ppm CO2's insulation response is asymptotic and nearing complete saturation as an insulating agent. CO2 has never been a control agent for climate in the past even at 4000+ ppm so how can you convince the scientifically literate that it began to be one, but only by those who seek to control the economy; the roots of poverty and enslavement for the illegitimate enrichment of their controllers.
Great video, thanks for clarifying the physics behind "global warming". I'll be sharing it with friends. thank you
17:00 water vapor depends on air temperature which also related to land surface temp which relate to heat island effect in cities , black concrete , no green grass etc
This is awesome. Comprehensive and approachable, best I've seen.
Thanks!
@@grindupBaker Thanks for helping out!! Regarding the quote, I was referring to absorption of IR by GHGs does not in itself result in warming, due to IR being released by GHGs as well. So the increase in KE by IR absorption is countered by the lowering of KE by the release of IR. There may be a momentary localized warming, but that is all.
Wow Such a detailed video on green house.... Thanks a lot
Thanks for watching!
Although this video a bit long, but I really don't feel that long, because I enjoy it so much, but it also makes me wonder about why the morning air is so fresh while there is more CO2 in the atmosphere at night than the day time
Thanks! It takes several years for a change in atmospheric CO2 levels to effect the earth's average temperature. Also, we cannot biologically detect CO2 levels in the air unless they get high enough (perhaps above 2-3%) to begin affecting our blood pH, which would make us ill. The current CO2 level is at an average of 0.0042%, so that is too low to be detected biologically. Of course the earth's temperature would get too high for life to exist long before we got to 2 or 3% CO2. Great question!
@@CrashChemistryAcademy Trying to understand everything when I replayed this video. Then, I got another question. How does higher temperature still increased when the earth's albedo is decreasing
@@cathyny83 The earth's absorption of the sun's energy is the source of all warming that occurs on earth, and albedo gives us the amount of sunlight reflected back into space by the earth, in other words the sunlight that does not warm the earth. So less albedo means more sunlight absorbed, resulting in a warmer earth. In the discussion at around 9:35 about the meaning of the equation governing the relationship of incoming versus outgoing energy, it is (1 - albedo) that is the multiplier on the left side that determines the amount of sunlight energy absorbed by the earth. If albedo decreases, then the term (1 - albedo) increases, which results in an increase in T (temperature) on the other side of the equation. Does that make sense?
@@CrashChemistryAcademy In other words, is less albedo cause the amount of solar energy the earth absorbed decrease, that leads to higher temperature？Since the total solar energy equals to the earth's surface temperature, it seems that less albedo would not increase the temperature
@@cathyny83 I think you are misunderstanding the cause of albedo, the reflection of solar energy. This is mostly clouds, snow, ice, and to a lesser extent all other surfaces on the earth. Some sunlight reflects off these surfaces and goes back into space. That reflected light (albedo) is therefore not absorbed by the earth, and so cannot be used to warm the earth. If the amount of reflected light decreases (less albedo) that means more light will be absorbed by the earth. That greater absorbed light energy results in higher average temperature on the earth.
Hands down the best global warming video I watched. Thank you for putting the effort into making the great visuals and very clear explanation.
Thanks for your comment!
What a great video. Congrats! 👏👏
why greenhouse effect is green?
"Green" comes from the metaphor of how global warming works similar to how a greenhouse works. While the metaphor breaks down upon close inspection, the greenhouse has been kept to symbolize the warming of the earth. A greenhouse is a glass house where plants are grown and is kept warmer than the outside ambient temperature via sunlight, which is useful in cold winter weather. The breakdown of the metaphor is that the earth’s energy equilibrium is the reason we have the greenhouse effect in the first place, whereas a greenhouse will not reach an energy equilibrium with its surroundings. The contents (except air) of a greenhouse warms via sunlight. That warming is transferred to air inside the greenhouse via conduction. Without the glass, that warm air would convect away and an equilibrium would be reached. However, that warmed air cannot move past the glass, and so it stays in the greenhouse, keeping it warmer than its surroundings. The greenhouse depends on not reaching an equilibrium, which is the opposite of how the greenhouse effect works!
Don't forget, also, heat transfer from the surface to the air via evapotranspiration, which is actually several times the amount lost by conduction and (pure) convection.
I was thinks the sme thing. The temerature on the surface rises, that gets more water evaporated, and that lowers the surface temperature.
A beautiful presentation for a not so beautiful outcome. Thanks so much for this important effort.
Thank you for the great video. I am trying to understand better the transmission and absorption of up-going IR radiation, and the role of the atmospheric window. My understanding is that at every height in the atmosphere the atmosphere radiates as a black body. So at every height part of this spectrum of radiation can escape through the atmospheric window; at every height there is energy lost into space. You mention around 25:00 that it is a misconception that IR absorption directly increases temperature. My misconception is that the absorbed IR raises temperature, following which the energy is re-emitted as a spectrum of black body radiation, part of which would again be able to escape. Surely I haven't understood the processes and would greatly appreciate further explanation, or perhaps you can point me to a video/article explaining it further.
The term "atmospheric window" applies to those IR frequencies emitted by the earth that are not absorbed by any greenhouse gas (GHG). Most IR frequencies emitted by the earth are absorbed by GHGs, but there are a few "windows" of IR frequencies NOT absorbed by any GHG, and so those IR frequencies escape directly to space. The black body radiation you speak of is the IR emitted by any GHG in the atmosphere. Any IR frequency emitted by a GHG can be lost to space if it is going up AND no GHG is in its way to absorb it. So the higher the GHG is in the atmosphere, the less likely there will be another GHG in its path to space. Your misconception is not really a misconception. The absorbed IR will increase GHG KE, which one can think of as a localized momentary increase in temperature. It is only momentary because when the IR is re-emitted by the GHG, then KE decreases, and so there is no net increase in KE. The increase in atmospheric temperature that we call global warming comes from the earth retaining more energy to increase IR output in an "effort" to reestablish the equilibrium that has been lost by increasing atmospheric GHGs. As the earth retains more of the sun's energy, much of that is transferred as heat to the atmosphere, and so the atmosphere increases in temperature. I think I have addressed all your questions, but if not let me know.
I can't thank you enough for this. Im an environmental science student and am trying to better my fundamental understanding of the entire process or concept of global warming -> thus climate change, in general and this is so ridiculously informative, you have no idea how valuable it is.
A nice synthesis of the major scientific findings regarding the connection between increased greenhouse gases and the warming of the earth. Very interesting, well done, and thanks for making this.
Great presentation in both format and content. Thanks
Thanks for your comment!
Nicely done! Great presentation! Thanks for your effort!
Very detailed yet easy to follow the logic
Sir please upload more video on chemistry.
Your ability to explain is top class, You can explain the concepts of each topic in a very good way and I can understand your every words.
The way you lesson us ,I love this way .
Your #stoichiometry video and #polar and #nonpolar videos was my life changing video .
Sir make more video please please please please 🙏
🙏
thanks very much, I appreciate your comments! I am making more videos, but it is slow going-- I also teach, which takes up most of my time.
Two comments -
1) All objects above 0K emit heat energy. What matters is NET heat transfer. Heat energy can flow from cold object to a warm object, more flows in the other direction.
2) Melting sea ice does not contribute to sea level rise. Melting ice sheets do contribute to sea level rise. Melting sea ice does change albedo, another feedback.
Otherwise a great video.
Thanks very much for ur subscription!!!! 💯🌹🌹💙 great explainations as always😄
Thanks and you're welcome!
What about all the interemed stored infrared energie in buildings masses and dark surfaces like streets wich leads to higher temperatures in urban areas?
Great question! Generally, urban heat islands cause a localized increase in temperature, for a variety of reasons, including what you mentioned, but also through increased concentrated human activity of all kinds. This can have different effects on the environment, but mostly is confined to affecting local weather patterns while having little effect on climate patterns. However the significance of its effect on warming the planet certainly is increasing the longer these heat islands exist, and they are getting larger and more prevalent. Some urban heat island are believed to have a larger impact on climate depending on location. For example large urban areas along the US Atlantic coast are thought to be contributing to changes in the Gulf Stream.
The infrared you specifically asked about is only infrared as released energy, not as stored energy, although it likely would have originally been absorbed as IR, and then stored as an increase in kinetic energy. Once IR is released, it becomes part of the general effect of released IR from the entire earth's surface. So it is likely that the heat island affecting local weather has a far greater effect than heat island released IR has on the climate.
I appreciate it that you listed the correct order of ghg potency. This is so misquoted by the press & even lots of textbooks. I go around writing publishers to correct this be/c many of them are trying to promote 1 narrative. Just today an article claimed CH4 was dominant over CO2.
" This is so misquoted by the press & even lots of textbooks"
Got an example? Every textbook that I know lists water first.
"Just today an article claimed CH4 was dominant over CO2."
Well - it is. If you take the same amount. Maybe you missed this clarification?
@@enderwiggin1113 Water vapor is first-the permanent dipole moment is what does it. See Murry Salby's text
@@kimlibera663 Which text is this supposed to be? Please give the title.
@@kimlibera663 Following your (or Salbys?) 'logic', CH4 would have no greenhouse effect at all since it has no permanent dipole moment. In short: It's nonsense.
Really great !! The most comprehensive video I have seen on the GHG effect, with all the physical phenomenons detailed, even calculations (how we know that -18°C would be Earth temperature witout any GHG). Thanks !
The only missing point probably being why high altitude atmosphere temperature decreases (as this phenomenon precisely invalidates the assumption that sun variability would be responsible of the current warming).
Two things-- 1) almost zero sun energy is absorbed by the troposphere. It is the earth's surface where absorption of sun energy takes place, and it is the IR energy released at the earth's surface which interacts with atmospheric GHGs. 2) The temperature of the troposphere (lower ~12,000 Km) decreases with higher altitude due to adiabatic expansion of atmospheric gases. If you have ever felt a can of compressed gas getting colder as you release the gas, this is the exact same mechanism. Adiabatic expansion refers to the expanding gases (atmospheric gases expand and decrease density as altitude increases) doing work on their surroundings, which is a different mechanism of energy transfer than conduction. The result is a loss of KE, which is a lowering of temperature. Beyond the troposphere, which is the stratosphere and beyond, the atmosphere does increase in temperature due to a few factors, including some interaction with sun energy. However the vast majority of GHGs stay below the stratosphere and so stratospheric GHGs have little effect on warming.
absolutely perfect! thank you so much!!
Great video. How long will it take for the world to rebalance to 255K? Just a IN=ACCUM unsteady state diff eq for MCpdT/dt of the air? And water and land?
Great video. Very good explanation. However, I wonder how the Schwarzschild’s curve is considered in this model and what its influence in the calculation of the increased temperature. I know that’s an extra level of complication in the modeling, but it seems to be a critical one.
If you mean the Schwarzschild Equation I have not seen any application of it to global warming, but it seems like it would be relevant. Not familiar territory to me.
Loved this video presentation.... great insight! Thank You!!! I will sure share this with non believers as well as the believers.
Thanks very much!
I have a small point, but I think a critical one to raise.
You use the example of it taking 2,267 joules/gram to evaporate water then show how that energy is transferred into the atmosphere. But you didn’t mention the energy balancing which would mean 2,267 joules is lost from the surface for each gram of liquid H2O to be evaporated. This could lead to some concluding that the energy at the surface is not effected by this transfer of energy of evaporating water.
Thank you for the video.
Great point. Assuming a steady GHG concentration in the atmosphere, there is negligible kinetic energy change at the surface due to evaporation because of surface water absorbing sun energy or conductive transfer if the air is warmer. So rather than cooling, evaporation would instead likely reduce the amount of heating at the surface, attempting to approach an equilibrium. But since increasing atmospheric GHGs disrupts the earth's entire energy equilibrium, the net result of water surface energy absorption is greater than the amount lost through evaporation, which is the mechanism through which the earth's equilibrium is re-established-- that is, increasing the earth's surface temperature (heating), which includes heating surface water. So now we have greater evaporation, but again, that would serve to reduce the magnitude of the temperature increase (heating) from absorbed solar energy, rather than cooling.
Hope that makes sense!
@@CrashChemistryAcademy I am not sure that helps. Perhaps I worded the question incorrectly.
At the moment a gram water is evaporated, the surface loses 2,267 joules, which is now 2,267 joules in the atmosphere, correct?
Granted, if it is daytime, the surface will continue to absorb energy.
The way you worded your reply it appears you are claiming the surface never loses energy. If this were correct, we wouldn’t be talking, we would have died long ago due to a runaway condition. And this is the point I was trying to address. The surface energy reduces 2,267 joules per gram of H20 evaporation, that 2,267 joules then is transferred into the atmosphere, correct?
Yes, that is correct. However the transfer of the 2,267 joules to the atmosphere occurs as potential energy. Surface water gathers kinetic energy via radiant heat (sun) or conduction from a warmer atmosphere (sorry I left that out in first answer), both of which increase the KE of water molecules. If a surface molecule has enough KE to be able to overcome its attraction to the surrounding water molecules, it will break free and go into the gas phase. This constitutes a positional change in the water molecule, and at that point the increase in KE used to break attractive forces becomes potential energy. So the 2,267 joule increase in the gram of water is potential energy and does not contribute to atmospheric temperature. The significance of the increase in water vapor is a change in precipitation patterns, in particular larger amounts of rain water during precipitation; also changes in storm patterns, changes in cloud formation, wind patterns, and more energy in precipitation events like storms and hurricanes.
For the first time of my educational life I have seen such kind of video. Where you have showed how global warming is developed collaborating with thermal physics.Thanks a lot of Sir. ❤❤❤❤❤❤❤
Thanks for your comment
1) Is the energy received from Sun used in Earths different "spheres"?
2) Stefan-Bolztman equation relates T^4 to the heat energy balance Sun Earth. How does T relate to the surface temperature of the Earth? If T is certain value what does it mean really in terms of the dynamically varying temperatures in the different "Spheres" of Earth?
3) How can you prove that the CO2 difference from 1870 to now is only from human sources? It is well known that in previous geological times CO2 was much higher than today and there was NO industry burning FF back then.
For your first two question, can you clarify what you mean by the earth's "spheres"? I'm not sure what you mean.
For Q3, there is a fair amount of concrete evidence that the increase in CO2 of the last 150 is from human activity. The most compelling I think is from isotopic analysis. Please see this video for an explanation-- ruclips.net/video/b4QDokHJFIg/видео.html "Evidence for Human Generated Increases in Atmospheric Carbon Dioxide." Further, the carbon cycle is influenced by a great many geologic factors, and the geology of the earth changes quite a bit over geologic time periods, and so the amount of atmospheric CO2 changes as well, so CO2 naturally fluctuates over long geologic time periods. 150 years is a blip geologically-- it should have little significance in a geologic perspective, however CO2 concentration has changed dramatically in that geologic blip. That alone is a strong indication that this change in CO2 is not caused by natural phenomena.
Using Stefan-Boltzman in equilibrium, CO2, being 0.04% of the atmosphere, contributes little to the total Earth emissivity of about 0.95. CO2 alone doesn't give a warming result. Estimates of atmospheric H2O are all < 5% but even if atmospheric H20 were to double to 10%, Stefan-Boltzman gives the new equilibrium temperate increase at < 1C. Is that correct?
The fact that emissivity of CO2 is so close to 1 at relevant IR ranges supports its importance in radiative forcing as described in the video, and so supports its importance to warming. Atmospheric water vapor concentration is limited by the amount of liquid water (primarily in clouds and surface water) that enables condensing vapor to reach an equilibrium with evaporating liquid water, which is what we call 100% humidity. This equilibrium can get as high as 4% atmospheric water vapor in hot climates. If water reached 10% of atmospheric gases, that would likely be past water's tipping point and so the earth would be in a runaway warming, so likely no equilibrium would be reached, at least not before we are all dead.
Quantifying emissivity will give the same warming values presented in the video.
👏🏼👏🏼 thnks for this lecture sir🌸
it was helpful ✊
Thanks! You are very welcome!
There is no mention of the radiative scattering and formation mechanisms of cloud. It is the most essential mechanism of the energy exchange between the atmosphere and the deep space.
Radiative scattering from clouds is termed albedo. Albedo is mentioned a few times in the video. Cloud formation itself is certainly important to warming, but the complexity of cloud formation warrants a separate video.
@@CrashChemistryAcademy The concept of albedo applies to all objects not just clouds. You did mention this concept. I am specifically referring to the radiative scattering and formation mechanism of clouds this video does not mention. The albedo of a cloud is integrated from the scattering cross section derived from those mechanisms. These mechanisms are the most essential for computing the overall albedo of the earth. However these mechanisms are extremely complex, chaotic and largely unknown.
Thanks much for your input.
There is a cooling of the atmosphere at higher elevations.
The cooling occurs due to a process called adiabatic expansion of gases. The upward expansion of atmospheric gases due to KE and gravity does work on the surroundings and so loses KE, which results in cooling. It is this cooling that reduces the energy of infrared loss to space, disrupting the earth's energy equilibrium, and so the earth retains more solar energy, which warms the earth, in order to get that cooled atmosphere to a temperature that restores the equilibrium. That cooler atmosphere is the basis for the earth's warming.
Very good, Thank you.
This video is amazingly put together! Thank you
Such an HELPFUL video and Damn I just wanted to watch a video on this. Super lucid for nooobs like me
Great! Thanks for the comment.
In this argument, it's also crucial that the atmospheric lapse rate is not itself affected by changes in the greenhouse gas concentration. Otherwise it wouldn't be possible to work our way down from the emission layer to the ground using a temperature curve of the same slope for all CO2 concentrations. This is indeed a good approximation because the lapse rate is determined by the majority gases (oxygen, nitrogen), not the trace gases.
Good point! I've thought about that but did not have a good grasp of it, so thanks much for the edifying comment.
Why can't the IR energy absorbed by a CO2 molecule be passed on to N2 or O2 molecules as momentum?
Yes, this happens quite a bit-- KE transfer through conservation of momentum, called conduction. The issue is does that increased KE stay in the atmosphere as KE, which would increase atmospheric temperature. The answer is only momentarily, the reason being that eventually that KE transfer would come to to another CO2 molecule, which would then lose that energy via release of infrared, which means that energy as KE is now lost. This is covered in 24:45 to 25:57 in the video.
@@CrashChemistryAcademy.So you state "and here i would like to address a common misconception which is that carbon dioxide absorbing infrared energy directly increases atmospheric temperature that is not the case
25:10
any change in kinetic energy is momentary ..." but Why? Why would that KE be transferred to a CO2 molecule when there are thousands of N2 and O2 between it and the next CO2 molecule?
@@CrashChemistryAcademy The warming of the surrounding air causes it to expand and rise.
Yes, a good idea to look at the numbers-- For every 1,000,000 air molecules, there are (approximately) 420 CO2 molecules and 990,000 N2 and O2 molecules (combined). The 420 CO2 molecules is up from 400 in 2020 and 280 at around 1850 and before. To simplify, let's just say there are 4 CO2 molecules for every 10,000 air molecules. If in fact the increased KE of 4 CO2 molecules transferred and spread through those 10,000 air molecules, the overall increase in temp is likely too small to be measured. However there are two mitigating factors: 1) the majority of CO2 molecules absorbing IR will then emit that IR before colliding with another molecule, so no overall transfer of KE. 2) Eventually, for those CO2 molecules that do transfer KE through conduction, because the CO2 is so thoroughly mixed within those 10,000 molecules, and at standard conditions a gas particle experiences about 10^10 collisions per second, CO2 will pick up that energy again over a very short time period and release it as IR. CO2 continuously emits IR simply due to its temperature, and if its KE is raised a bit, that just means the IR it emits will have a higher energy.
Regarding gas expansion: again, any expansion would be negligible due to there being such a proportionately small energy increase in a large amount of air molecules, but even more important, and more interestingly, that expansion would be adiabatic, and result in a loss of KE. Adiabatic expansion occurs when the expanding gas does work on the gas it is expanding into, and the result is a loss of KE, which means the expanding gas's temperature would decrease. Adiabatic expansion is why the troposphere gets colder as altitude increases.
Lastly, regarding expanding gases rising-- it is the conduction from a warm surface of the earth to cooler air molecules at the surface that results in an expanding warm mass of air, which will then rise. This is convection. Convection is a far more powerful mechanism for transferring heat than conduction, and it is convection currents that account for much of the weather and the climate that we experience.
did not understand the point of equal the stefan value to the amount of radiation emitted by earth
Very cool video, I covered this only in year 10, in IGCSEs chemistry in very little detail. This was interesting for going so much in depth, so thank you!
Unfortunately the world is only money oriented... I don't think people understand that it's not the only problem, we are destroying the world in so many ways, and no solution is going to allow us to live with the same quality of life we have now, we are polluting too much, and the disparity is too great... So much for we're all equal...
global warming is a pretty dark topic, wish it wasn't...
Same quality of life? I'd be interested to know how you rate the quality of life before the industrial age. I hate pollution too, but come on. Also, how was that air quality in London in the 18th century when everyone was burning wood and coal to stay warm? Or how about present day Saharan Africa where they cook over fires fueled with dung? Imagine how drastically their life would improve with a couple coal or oil-fired powerplants.
@@Tommy-my1jw So massive worldwide heat waves, out of control fires, and flooding is a lot better alternative. I certainly agree with you! Thanks for making this important point.
@@bubbahotep6316 those are the realities of living on a planet differentially heated by the sun--along with countless other drivers (including C02). It's unfortunate we've been coached into believing that we can do something about it. I'm all for reducing our so-called carbon footprint, including reducing pollution overall. I just have no expectation whatsoever that our climate will be appreciably affected.
How about the radiation that is NOT absorbed by CO2 and other greenhouse gasses? Won't they escape from the land/sea surface and thus lose more heat. Is that proportion negligent ie. doesn't change the big picture? Or is there a mechanism that blocks that IR radiation, too?
There are windows, gaps in the absorption spectrum of the whole of greenhouse gasses, in which emitted IR goes directly to space. These gaps are significant in that the warming of the earth would be greater if those gaps did not exist, meaning all IR frequencies were absorbed by GHGs. The gaps in IR frequencies, the IR that is not absorbed, are small compared to the range of emitted IR frequencies that are absorbed by GHGs.
If the Earth rebalances to 255K at a higher altitude, why would it be dimmer at a higher altitude than at a slightly lower altitudue? Is albedo a function of altitude?
The amount of energy per emitted photon decreases as the temperature of the emitting material decreases. So at the colder temps of higher altitude, less total IR energy is released per unit time than at the warmer earth's surface.
Thanks
Why are you including Albedo when there is no atmosphere, isn't this included in Stefan law for blackbody?
Albedo is the reflectivity of the earth itself. The entire earth reflects sunlight (otherwise it would be invisible), and so that is the earth's albedo. With an atmosphere, the albedo increases due mostly to clouds, however now we can more significantly include particulates as contributing to albedo due to the consistent wildfires occurring around the globe. So without the atmosphere, the albedo would be less than 0.3. With the atmosphere, it is hovering around 0.3.
now i understand wht we have to consider about the atomespher ehen finding earth temperathure
Thank you very much for this video
Hi and thanks for this great video!
One thing I still can't get my head around: The rise of atmospheric temperature is from air heated at the earth surface and then moving up (convection)? This process is increased because earth "needs" a higher temperature now that the increased greenhouse gases forces the IR-escape to a higher (and therefore colder) point. Okay, but what is the mechanism by which this "need" is articulated? I guess the same amount of air is heated at earth surface with or without higher amount of CO2. What would have happened with this air in pre-industrial times? It would have risen and then been transferred by conduction of kinetic energy in to CO2 at the original lower height and got "vented out" there?
Yes, I regret that lack of clarity. The energy ultimately comes from the sun. If you think of the earth system (by which I mean the earth + its atmosphere) in space as a system constantly receiving and emitting energy, that incoming versus outgoing energy has to reach a balance (equilibrium) simply due to the fact that if it did not, lets say in the case of emitting less energy than received, then the earth system would continue to heat up infinitely, which cannot happen. Conversely, if the earth system emitted more energy than received, then the earth system would continue getting colder until it reached absolute zero, which violates the 3rd law of thermodynamics. The happy medium here is of course the earth system, if not already at an energy equilibrium, will always go toward that equilibrium by emitting less energy or more, depending on which direction will get it to that equilibrium.
The atmosphere is not heated by the sun. Nitrogen and oxygen do not absorb EM energy in the range emitted by the sun. There is a small amount of sun-emitted IR that is absorbed by atmospheric GHGs, but that gets re-emitted and does not affect temperature. It is the earth's surface that absorbs the sun's energy, which can then get transferred to the atmosphere via conduction. With higher amounts of CO2, more air is heated via conduction as the mechanism of maintaining the equilibrium, and this is how the earth system is obeying the laws of thermodynamics.
@@CrashChemistryAcademy thanks alot for the reply! I get the concept of the incoming and outgoing energy being in balance, but I'm still wondering about what mechanism, what kind of energy transfer, that makes the energy that leaves the surface though convection later leave the atmosphere and go out in space. It must be transfered from energy in the form of the moving gas, into long wave radiation, no? How?
GHGs are able to generate IR without first absorbing IR. It only depends on the temperature (KE) of the particle. Higher KE = higher energy photon, & vice versa. This is the basis for black body radiation. Any energy leaving the atmosphere does so via IR emission. So your last statement is correct.
You've managed to maintain a nice logical flow in telling the story (which wouldn't be easy with all the moving parts).
Nice work :)
Thanks very much, I appreciate the comment!
Overall: This is a very good, comprehensive summary of the problem. Well done.
why co2 is considerd as major green house gas
what about stratospheric cooling and the absorption of infra-red radiation?
Because the vast majority of IR released to space is released in the troposphere, the stratosphere has little impact on global warming as far as GHGs are concerned. The one major GHG in the stratosphere, ozone, primarily absorbs UV, and due to that the stratosphere is warmer than the troposphere, but that has little impact on tropospheric/global warming.
Is the emission height and mean mass of atmosphere height coincidentally the same?
can you do a vidio about stefan boltzman low there is no any vidio to find it on you tube
How to calculate radiative forcing from water vapor?
I would love a reference to the paper comparing potency of greenhouse gasses which concludes that methane and HFCs are less potent than CO2. Thanks for your video.
Thanks much for your question. In looking back at the video, I can see now that some of my statements were poorly considered. The question of CO2 versus CH4 & HFC’s (etc) radiative forcing is complex and I simplified far too much. I assume there are papers out there that support CO2 being more important than other GHGs, besides water, regarding overall radiative forcing, but my statement came from discussions with a couple of climate scientists, not published papers. I should have attempted to better explain the perspective I had (!) which is as follows:
There are several points that need to be considered:
1) The usual comparison of CO2 and CH4 potency for radiative forcing are per unit mass, usually kg, which already skews the data, as follows: for every 1 kg of CO2 and 1 kg of CH4, there are 44/26 or 2.75 times more CH4 molecules than CO2 molecules. So the comparison is immediately skewed. (44 and 26 are the periodic table masses CO2 and CH4.)
2) It is true that in comparing kg to kg, methane (and HFCs, etc) are way more potent than CO2. However in practice, that particular factoid about kg CO2 vs kg CH4 doesn’t matter because CO2 has several orders of magnitude more kilograms in the atmosphere. So the kg-for-kg factoid leads the broader public to not worry enough about CO2 emissions versus public worry about CH4 emissions. We should worry about the overall potency (volume-to-volume x number of molecules per unit volume), not the kg-for-kg statistic.
3) The statistic generally arrived at on an internet search comparing the radiative forcing of the two gases is from EPA data that states CH4 is 25x more powerful than CO2. This is a tricky calculation, and is given per 100 years for a given equal mass of CO2 and CH4. A few complications-CH4 half life is ten years, CO2 half life is hundreds of years (could not pin that down, several reputable sources gave a large range); the time span of the calculation (100 years) is a huge consideration because of the large difference in half lives; the half life of CH4 is due to its oxidation into CO2, which adds a small (by comparison) amount of CO2 to the total; and finally, the calculation avoids the all-important consideration of actual amount of molecules of CO2 versus CH4 present in the atmosphere.
4) I think the reason the kg-for-kg factoid entered the discourse is that it is necessary to explain one thing - namely why methane leakage from the gas/oil industry is so much worse than just combusting it into CO2. If methane and CO2 were equally "potent" on a molecule-for-molecule basis, then methane leaks from, e.g., natural gas pipelines, wouldn't matter for climate change. But leaks do matter, because a mole of (uncombusted) methane creates far more radiative forcing than a mole of CO2.
5) This 2016 data is from the site ourworldindata.org/greenhouse-gas-emissions#annual-greenhouse-gas-emissions-how-much-do-we-emit-each-year: In terms of CO2 equivalents (CO2eq) (GHGs are converted to CO2eq by multiplying each gas by its 100 year 'global warming potential' value: the amount of warming 1 ton of the gas would create relative to one ton of CO2 over a 100 yr time scale):
CO2 74.4%, CH4 17.3%, and HFCs 2.1%. This is what I was getting at in the video without explanation, except there is a much larger difference than indicated here, since, again, the comparison here is between masses rather than actual numbers of molecules (per given volume of air), the latter giving the real result in terms of comparing radiative forcing.
Thanks for bringing up this question. I’ll have to edit out some of those statements, as they are misleading in terms of how they are phrased in the video. (RUclips hugely restricts editing of a published video, I’ll give it a try.)
@@CrashChemistryAcademy Thank you for your thorough response.
I was particularly interested in this question because of the trickiness in calculating potency of methane and carbon dioxide. www.nature.com/articles/s41612-018-0026-8 and eprints.whiterose.ac.uk/108770/1/SLCP_INDC_withfigs.pdf are two good papers on this topic - they compare using GWP100, GWP*, and GTP for estimating what we are calling potency.
I understand now that you meant to say that CO2 is a bigger problem in our atmosphere now. Based on point 4) it sounds like you agree that one kilogram of avoided methane is more significant than one kilogram of avoided carbon dioxide. Ultimately, this is what I was wondering. I appreciate your input.
(Belated reply due to youtube diverting any comment with a link from the usual panel of comments).
Anyway... Thanks so much for the references, very interesting/enlightening. A complex issue to be sure.
Spectacular video and wonderful comment/conversation here. I caught that statement (CH4 vs CO2 global warming potential, and relative impact) too, but I was so happy to see this comment exchange. I watched a mythbusters video on GHG’s impact on temperature, and an IPCC video on global warming data, and the comments section was pretty brutal. I hope everyone there makes it to this video. Thanks for taking the time to condense the basics of an earth systems science course into 45min. Well done explaining the math and physics.
is all incoming energy to earth will reflect back will it not absorb any energy fravtion
Really great explanation! I have a question about the albedo. How much does cloud cover affect the albedo? Since clouds appear white I'm assuming they reflect light similarly to the north and south poles( or is that a misconception?). And Since global warming leads to more water vapor in the athmosphere, does this atleast have the effect of more clouds reflecting more sun light and slowing the feedback loop you describe at the 37:20?
My understanding is (this is not an area I am very familiar with) that higher average temperatures do in fact affect cloud formation, but I believe it affects more where clouds form rather than how much clouds form. It certainly seems like there should be a correlation between increased water vapor and increased cloud formation, but I do not know if that is the case. Keep in mind that many areas of the earth are become dryer due to higher global temperatures, which reduces average moisture in the air. And yes, more cloud formation would increase albedo. An interesting side note is that there are people in the "geoengineering" biz that have been coming up with ways of increasing cloud reflectivity (thus increasing albedo) in various ways through chemical manipulation. For a long time these ideas have been marginalized, but those ideas are becoming more prominent as our earth hurtles toward a 2 C global increase.
Is albedo actually a function of latitude and surface color or is it a constant value everywhere?
Albedo is only a function of reflectivity, and that can and does happen anywhere on earth and in the atmosphere. A sizable amount of the albedo is produced by clouds, which are constantly moving. The fact that earth can be seen from space is due to reflected light, which is part of the albedo, and yes it depends on what kind of surface is reflecting the light--darker surfaces = less albedo than lighter surfaces. Albedo is constantly fluctuating, but has stayed at a relatively constant average value over the last several thousand years, around 30%, until recent warming began to melt ice sheets, which reflect a lot of light, and so less ice = less albedo (liquid water is quite a bit darker than ice).
if we use hydrgen as fule we can feduce the amount of co2 that relese from focil fule
Hydrogen has had a difficult time getting to mass marketed cars for a few reasons. One significant problem is the manufacture of hydrogen gas requires a great deal of energy. Until that can be made more efficient, there is little incentive to use it to reduce greenhouse gas emissions, unless completely green energy is used in the process of hydrogen manufacture, but there are much smaller sources of green energy right now on the planet compared to fossil fuel use. Note that the same source-of-energy problem exists with the energy used to make electric cars, including making batteries AND recharging those batteries. Another problem for hydrogen is storage since it is a gas, as well as storing it safely since it can be explosive, far more explosive than gasoline. Then there is the culture of industry. Industrial decisions have a great impact on the use of various technologies, and the car industry has decided to put their R&D$$ into electric cars rather than hydrogen cars.
your video explains where where i had difficulty understanding. the altitude upwards radiation to space begins is where it's blackbody radiation temp.
5.4km above is middle of troposphea where conduction and convection still occures. wouldn't it complicate the model?
Yes! I've tried to present a model that is fairly accessible. There are far more details, including what you mention, that climate scientists account for. There are a great deal of variables to consider, and I believe I covered those that impact warming the most.
Are the relative intensities of sun and Earth emission spectrums to scale to each other? I get a sun max of 411 at 0.495 microns (yellow) and a max of 25 at 10 microns for Earth.
They are not to scale relative to each other (the y axis says relative intensities). I did not want to make the scales equal since the earth's curve would have been fairly flat compared to the sun's curve, which would have obscured the intention of the graph.
Thanks for all the work put into this video.
In the end, adding the prediction of devastating consequences from global warming is not helpful.
There are other points of view and scientific research that suggest different outcomes and predictions of the earths future climate.
Could you please let us know how you perform these animations? what software you used?
I use microsoft powerpoint. It has a lot of drawing and animation tools. Look at the animation tab at top and you'll find a lot there.
17:06 But why is the presence of water not directly altered by humans? Don't we produce water vapors by burning fossil fuel?
Water vapor in the earth's atmosphere varies between close to zero % to 4% depending on conditions. CO2 percent around the globe is now about 0.042%, up from 0.028 % around 1850. The added water vapor is far smaller than the water vapor already in the air, and has little discernable impact. Since the percent of CO2 in the air is so small, added CO2 from burning fossil fuels is very significant.
thank u sir... it helps me alot❣
You're very welcome 😊
Can CO2 (for asymmetric or bending vibration) , H2O themselves can generate EM wave? Since accelerating charge can generate EM wave.
Yes, and that is exactly how black body radiation works. It is just the moving nuclei in atoms at the surface of a body generating EM waves. GHGs will always be emitting electromagnetic radiation due to the vibrations of their nuclei. The amount of vibration dictates the energy of the emitted radiation. Since we measure that vibration as temperature, higher temperature particles emit higher energy radiation than lower temperature particles. Everything in the universe that has charge is constantly emitting EM waves that are proportional to their temperature.
Thx for the vid but 16:58 to be more scientific water vapor and methaen even in low emissions more potent than CO2
When comparing equal numbers of particles per unit volume, carbon dioxide produces a larger radiative forcing than any other greenhouse gas except water vapor. Water vapor is discussed in detail in the video, in particular beginning at 35:20, including its own feedback effect as well as the feedback of CO2 on water vapor levels.
Thanks for you thoughts.
How do you know that balance is a good thing for humans?
Why dose photosynthesis not enter your equation?
Why don't you mention the little ice age ending at the start of your diagrams.l/charts?
How do calculate the amount of co2 naturally produced by the planet?eg volcanically etc?
Why do you think only planet earth is warming an the rest of the solar system is in balance ?
I have many more questions but heres a start.
Again thank you for your theory.
The balance allows for a stable climate. Without that balance, extreme climate events begin to happen, such as more extreme hurricanes & tornadoes, more extreme droughts, more extreme flooding, generally more severe weather around the entire earth.
By photosynthesis I assume you mean CO2 fixation. Yes plants remove CO2 from the atmosphere, but plants also produce CO2 via cellular respiration. It certainly would be better to have more plants, but it will not fix the excess CO2 pouring into the atmosphere.
Ice ages and geologic events take place over many thousands to millions of years. Anthropogenic global warming has occurred in 150 years. It would not be possible for the earth's geological events to produce nearly this amount of change in such a short time span.
CO2 production can be determined through the earth's carbon cycle.
For the question of balance on other planets, they may or may not be in balance. If not they can be getting colder or warmer. Venus has had runaway warming but I believe that has reached an equilibrium, but I don't really know.
@@CrashChemistryAcademy Thank you very much for your reply and time.
I just need to understand.
Why do you think atmosphere can be balanced?
Nature is extreme and balanced.
Records only go back to 18/19 century before that global measurement were not possible. 1850 was the end of the little ice age.
Plant respiration removes half of its co2 intake at night, not to mention the dramatic growth extra co2 intake causes.
When you say human causes in last 150 years are you referring to the missing fusion reactor of Fukushima?
The microwave technology governments use for weather manipulation ,
Or 3/4/5G communications or what?
I really don't understand what you mean to achieve other than inventing a tax on air. (Water taxes are crazy enough).
All planets in solar system are heating so it's not just co2 causing earth to heat.
I enjoyed your upload I think there's a lot more to the story though, many variables.
I think this is all just another distraction by the powers that be, honestly.
My best wishes to you, thank youand respect.
Thanks for taking an interest in the video. I think it is important to separate the science from the politics, and you seem to be conflating the two.
You forgot the clouds. 2016 I noticed more clouds -> colder weather. NOAA measured the temperature over sea and land and also notices a cooling trend from 2016. Our solar panel data show me what is the thermostat - The Sun (controlling the clouds).
"2016 I noticed more clouds -> colder weather."
You forgot that clouds not only are the cause of climate, but also the result. They are a feedback!
How can solar activity which *decreased* over the last 40 years (mean of the cylces) cause *more* clouds? This makes no sense.
@@enderwiggin1113 40 years? Do you know hos long is a cycle? Check Valentina Zharkova. We are expecting another 14 days extremely cloudy. A bad sign!
@@enderwiggin1113 Listen to Henrik Svensmark! You must lern about cosmic rays and the solar magnetic activity!
Doesn’t the sun emit 1/4 of its energy to us in IR?
Far less, less than 1%
Although if you were thinking purely in terms of the range of EM radiation put out by the sun, by far the majority is IR, but compared to both visible and UV, IR has far far less of both photons per unit time and total energy per unit time.
@@CrashChemistryAcademy thanks. If I take a 5800K blackbody curve and scale it by Earth-sun distance compared to total output from a sun sphere, I get about 70 W/m2 when I integrate from 1-100 microns. What else needs adjusted for it to be around 1%?
how deos co2 can store heat
CO2 is not really thought of as something that stores heat, due to it being a gas and have a very low heat capacity. Rather it absorbs heat in the form of infrared radiation, but it then also releases heat as IR.
very comprehensive, presenting material that is unexpected but essential to the story. Thanks so much.
Hey Jarret, is that you? I missed that you were making all these comments, so thanks heaps for helping out!!
Great video!
Now, if you can scale this down to what a 7th grader could understand. Do that and your average American will stand a chance of comprehending.
An interesting comment. My motivation for making this was to go beyond the far too many 7th grade-level global warming/climate change videos out there and try to convey some of the real science involved. I made it for my high school physics students, who have also taken chemistry. If you have any questions about the material I would be happy to clarify.
@@CrashChemistryAcademy
I still say it’s a great video!
Thanks!
How do you explain that co2 levels were 1000 ppm millions years ago and that situation didnt produce an increase in temperature, but the opposite, a decrease ? This explanation does not explain the Evolution of the earth climate in the past. The climate system is highly stable and this explanation requieres a CO2 concentration almost constant to avoid a very unstable system.
Climate is not stable over geologic time periods, and fluctuations in CO2 are a large part of those climate changes. However, we have had large climate change in the past 150 years, a degree of change that is far beyond the earth's ability to cause change in geologic time. 150 years is an insignificant amount of time in the geological record, and so having such a large change in such an extremely short time span indicates forces at work that are not of the earth's doing.
We have had a very stable climate in the recent past. Changes of 1 degree in a century are not inusual. Looking at geological records we can see greater increases and decreases in temperatura without human intervention. This climate theory centered un co2 is uncompleted and innacurate
Now that we know what is bad, what then _is_ the optimal temperature and CO2 level?
We know that the temperature throughout the earth's history has fluctuated quite dramatically, far more than what we are experiencing now. However those fluctuations occur over thousands to millions of years. Our current rise in temperature has only been in last 100 years, which is unprecedented in the earth's history. Further, the temperature of the last 8000 years, the dawn of modern humans, has remained stable, and so our civilization has evolved at a time where the global average has been around 14.5 C. This also correlates to a fairly steady 280 ppm CO2 in the air. So we are used to evolving and living in a climate that has those data points. The earth will survive an increase in temperature, the question is what will happen to its inhabitants? How will they adapt? Will it be easy, hard, catastrophic? Our current course suggests we are headed into a dystopia of the type popular in current fiction and movies, not a great scenario.
Hi ! Great video on the GHE. Would you like to share this video ?
I'm not sure what you mean by share-- it is available to anyone via youtube.
@@CrashChemistryAcademy Sorry for being unclear. Since I am not a paying member, i can't download the video. Would you be willing to send it to me via email ?
There is no youtube service that allows you to download content, due to violation of copyright law. Can you tell me why you need the video file? Please reply to joelwax3@gmail.com
is radiation is energy
All radiation is forms of energy. The radiation that the video is concerned with is called electromagnetic radiation, which (in the video) includes infrared, visible, and ultraviolet radiation.