This is the best Sci-Show video I've seen in a while. It's very informative for me, as I live 6' above sea level. On top of that, I live about 400' from a tidal bayou canal. The last big storm pushed the sea water up into the bayou, where it was opposed by the rainwater draining out. For about 9 hours it was inches from having overflowing sea water gushing through my neighborhood. Then it finally started to recede. I worry that next time we won't be so lucky.
I live in a similar area. There are still many dead trees, not yet cleared away for some reason, killed by the salt water during the storm-caused flooding on the coast (from Hurricane Katrina). Our city, though it is almost 100 miles inland, is only fifty feet above sea level, if I recall correctly. And before Katrina, people in our town really believed that no storm would ever really damage US. Now, everyone's afraid just the same as you've said. Anyone actually on the coast (or, gods defend them, in New Orleans) has to be living in a state of constant worry.
@@Beryllahawk Grew up in Lafayette and enjoyed swimming down our street multiple times every year. The even more pissed off than normal moccasins weren't fun, though.
Less than currently expected. Below 10 billion humans below 500kg (likely below 100, given the starving children to be included) on average at hardly higher density as water/hardly lower volume could only lead to 5 000 billion L additional volume, that's 5 000 000million cubic meters so 5 000 000 000 000 km3? I think big numbers need sleep now or paper to be computed on 😅
@@fionafiona1146 question is how much would it rise, not how much volume it'd add. answer is likely an insignificant amount which wouldn't even be measurable anyway
Am from Finland. While exploring forest, found a neglected sea marker in middle of the forest about a half a kilometer from the current ocean shore. Thought, well, let's just swiftly move on, this stuff just is here nowadays.
@@montycantsin8861 According to Swedish alarmists it's 13 years, and a few dingy Congresspeople, which are all crap arguing over who is less shite, but forgetting to remove their sponser tag lines.
@@buddyguy4723 as the video says, sea levels are dropping in Baltic Sea because of the post-ice-age rebound. If you have zillion tons of ice dumped on you, you shouldn't be surprised if the very ground gets pushed down and it takes tens of thousands of years to get back up!
@@Steevo69 the heck are you talking about. The Swedes can go to the beach and say "yep, the sea is definitely receding. But that has nothing to do with anthropogenic climate change, because there's obviously no continental ice shelf here anymore. Clearly the work of post-ice-age glacial rebound. Ice goes away, ground goes up, makes sense."
Good use-case for the Dunning-Kruger effect. Nature is far more complex than even reasonably knowledgeable people realise. That is why climate change is so dangerous to politicize.
That actually depends more on barometric pressure, which you can measure without having to know where sea level is. Pressure just gets lower with altitude, but there's no exact figure that says for example, 95kPa means you're so far above sea level, since wather and presumably tidal forces and gravity will also make it change. But it's easier to measure than sea level, all you need is a barometer. Yes yes, I know I missed the joke, but nevermind that and go build yourself a barometer so you can cook your burrito.
@@brinx8634 And of course the scientists who perform the measurements know when there had been a 3mm rise and that a new measurement is needed. Makes perfect sense
Nillie i disagree. Thermal expansion of water would almost definitely be categorized as climate issue, not weather. He was probably talking about precipitation and evaporation when he said weather.
@@ragnkja I agree with you, but you're forgetting the rules governing climate change discussion. The climate alarmists insist that climate and weather be covered separately. Unless, of course, if local weather seems to support their position, then it's considered valid evidence. If local weather seems to refute man made climate change, that is not allowed to be used as evidence.
@@tomjacobson7623 I've observed exactly the opposite. We've had some hot summers lately and every time the scientist are asked if that has something to do with climate change they say you can't see that in isolation. On the other hand americans have pointed out to me they had a cold winter. I've never heard any climate denier sound remotely scientific. Mostly, they sound like it's a like what football team you support.
I just want to pause, appreciate and thank SciShow for consistently using the metric system and not bothering me (and all the other international viewers) with Miles, Feet, Ounces, Fahrenheit and what not.
It’s not. It’s the clock they use to time the return signal that needs to be good. Given the speed of light is so fast the satellite is essentially stationary over a send and receive.
Satellite orbits are in a constant state of flux; Therefore, their altitude is changing, making any calculations based on RADAR/LIDAR measurements more complex.
I came to write, what a great video this is; well explained, covers all the bases, clear, uncomplicated (Yes, I know it's complicated but .. ) and accessible. Scrolled down through the comments and it seems, I'm not alone. Well done SciShow, and eminently well spoken Stefan, you're definitely the best presenter for this. Kudos all round.
Measuring coastlines is also a complicated undertaking. The measurement can be infinite since the more you zoom in the more you see details like coves and inlets.
@@limiv5272Excuse me, my point is you are NOT in the ocean, you are ABOVE sea level - which is why that # tells you how much it would have to rise before you ARE in the ocean and in need of boots! What kind of weirdo walks face-first into a cream pie like you just did? Just take off your google-glasses. :-)
I can think of several reasons. Tides, storms, gravity variations, wind patterns, jet streams, ocean currents, the sun, tectonic activity, Glacial activity, and global warming.
"If all of Greenland's ice melted sea level would actually drop by a could of dozen meters in Iceland." A couple of dozen meters? Like 24m or 78 feet? Like many times the effect of the sun or moon? Because of the effect of the gravitational pull of the ice? Is this number correct? Sounds a bit off to me.
It could be accurate, remember that the effect of gravity is inversely related by the square of the distance between the masses. The moon is far but the glaciers are very close.
I too found that effect size surprising. I wonder if a simplified model could help: Approximate the ocean around Greenland as infinitely wide, deep, and flat, and the ice sheet as a cylindrical disk hovering just above it, with a diameter of, say, 1,500 km, and height 2 km, and the density of water. Gravity from the ice sheet will perturb the surrounding sea surface into a meniscus-like shape. The question is what height that curve has as function of distance. We'd have to trace the gravitational potential at sea level from infinity inwards. Alas, going further needs more thinking than I can muster right now.
@@sternmg Yes, like the thinking. I was pondering more like a point mass for the earth and a point mass for the ice sheet. Some nicely rounded numbers: Mass of earth 6E24Kg, Mass of Greenland Icesheet 3E18Kg (Changing rapidly!) Radius of Earth 6000Km, distance from Greenland to Iceland 1200Km. This makes the earth only two million times the mass of the icesheet (which is pretty impressive for the icesheet itself).
If I'm thinking about it right that moves the center of mass one half of one 2000000 of the 6000000m radius towards greenland or 1.5meters. Making the sealevel 1.5meters higher than it would otherwise be (not 24m). What have I missed?
The solution is easy: if the Sun and moon is affecting the sea level, remove them and measure then set that as the Level. Put the Sun and moon back. What's the complication here?
This was an excellent video, lots of great information and it points out just how complicated the subject matter is, well done! Despite the silly comments some people post.
Thank you so much!! Doing all the research on sea level on my own as a laymen was very difficult and I made slow progress after weeks. This video was very helpful for my understanding of sea level and Climate Change. It has given me new crucial information and confirmed some conclusions I’ve reached on my research. It has equipped me better for Climate Change debates.
I learned that thing about the glaciers just yesterday from How To by Randall Munroe p.25. It really did surprise me (both the fact itself and that I heard the same fact two days in a row from two totally unrelated sources).
I've always wondered about big cities like NYC. How many tons of material are on top of Manhattan that weren't there a few hundred years ago, and what impact does that have? Is the tide higher because of the pull of the gravity from all the buildings? Is there enough man made/placed mass anywhere on Earth that would impact the Earth's rotation? I usually think, no, because of the total mass of the Earth compared to the mass of those buildings. But I do wonder about it.
If something the size of a glacier can have a gravitational effect I imagine that a full city of metal would. I'd imagine it wouldn't have as much effect as a glacier because that's solid ice vs. All of the air and other low density materials inside of cities.
i do wonder the same thing but i would like to add i think it even more detailed then that cause not only is that spot getting "heavier" but the material used there came from somewhere so maybe making that spot "lighter "
You may think of cities as lots of building materials being brought _in,_ but a lot of excavated dirt is also _removed,_ eg basements and subways etc. China's Three Gorges dam backed up enough water that Earth's angular momentum was changed, like a spinning skater pulling in their arms. Earth's day length changed(!) Slightly.
I can think of a couple reasons: how do you find the center? The same things that affect sea level also make the center of gravity shift. And Earth isn't a perfect sphere, so how do you define the center? Also, you'd need more digits, like 6371 km might mean ±1 km, but when siting your house near the shore, you may need accuracy to the meter. 🤓
There is no true center of the earth. Even the Greenwich meridian changes depending on which map system is used. This is because the earth isn't a perfect sphere.
@@Tibovl It does have a centre of mass, though, which I think is what GPS is referenced to (latitude/longitude is a conversion from its native 3D Cartesian).
SciShow--can you please do a video on the Australian bushfires--ex. how they got started; what has been the impact on wildlife? And speculate on the short and long term impact these massive bushfires will have on our environment.
Sea level is also affected by salinity and temperature, which change the density of water. There's a difference of 20 cm between the north side of Panama and the south side. Because of such variations, surveyors now reference elevations to the geoid, a theoretical equipotential surface that is close to sea level.
The satellites with the radars would measure the distance from the sea level; if it takes, say, 10 seconds for the signal to bounce back from the sea level and then you shoot the ray at land and it takes 9 seconds, you know the terrain is 1 second above sea level (which you would then convert into meters based on how fast the ray is traveling). As for your second question, I don’t know, but I assume that they defined X elevation as ‘sea level 0’ (based on averages or what ever) and basically ignore the raising/lowering of the actual sea after that point. Someone more knowledgeable than me may have a better answer for this, though.
Andrei Tache but what is 0? Or the standard point? How high is sea level? Is it 22 miles below the aptomsphere edge? Is it 33 miles? What’s the point of standard??
_”In the UK, the Ordnance Datum (the 0 metres height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921.” (__en.wikipedia.org/wiki/Sea_level__ )_ That’s about as good of an answer as I could find after a short google search. There really isn’t some fixed point around which to anchor our measurements (even the atmospheric edge isn’t a perfect sphere, thanks to the earth’s squished proportions and terrain deformations like mountains..) If you find some more complete answer, let me know
1:19 but wikipedia says we have lunar eclipse 2-5 times a year... so can't be that they align once every 19 years... did i misunderstand something? btw, I love these videos. I watch every single one, thanks for the endless (yet useful) 5-minute breaks everyday!
They're saying the lowest common denominator of lunar cycles and solar cycles is 19 years, as they're of different lengths. Still not a big deal, if you know a little physics.
I live near a famous stadium in London and my house is supposed to be 41 metres above sea level. Geographically I'm living on the steeper side of a very large river valley.
@@limiv5272 Just like island nations like Tuvalu and of course the Netherlands, if the absolute worst happened most capital cities of the world would disappear, as would vunerable places like the above mentioned, hopefully we can stop that happening.
Finally someone who mentions that sea level isn't flat because gravitational anomalies. If I'm not mistaken, the lowest sea level due to gravity is in the Indian Ocean. It's about a 100m lower than the average height. You wouldn't notice it but if you sailed across an ocean you would sail up and down hills of water.
*_...and as the Earth loses thermal energy, and shrinks, (nearly-maintaining its temperature, from extracted gravitational energy), its surface area diminishes and its seawater volume height increases..._*
Sea level based on satilites does seem to have absolutely nothing to do with real world sea levels though.. Which is important to remember whenever Greta or someone talks about the abocalyps
That would be hard. You would need to make a new pile of water drops, so you don't mix them up with the ones you haven't counted yet. You have to get a whole, other earth to put them on.
just thought of something, warm air can hold more water, so a warmer climate would actualy drop the sealevel? you know once all the ice is gone. so weird.
@@d4mdcykey I thought it was the other way around for water, it expands when frozen, shrinks when warmed. It's one of the only substances that act like this, very unusual.
@@dreggory82 ~ Nah, you're confusing ice with liquid, two different things. Heated water (liquid) expands, it's called Thermal Expansion: sealevel.nasa.gov/understanding-sea-level/global-sea-level/thermal-expansion
@@dreggory82 As temperature up goes down, water expands and contracts like most things, except when it drops below 4 C. As temperature lowers past 4, water starts expanding again and eventually ice ends up less dense than water.
What's missing from this discussion is how much (or little) each of those different factors affect the measurement. I.e. as an example, Lunar tides might affect 90 percent (guessing) of the measurement, and gravitational anomalies only affect 0.01 percent, than you only need to worry about these different factors if you need a precision of millimeters.
also, i been asking this, perhaps i'll do better on a new video, but does it make a difference what color vegetables you eat? i've heard you should eat vegetables of different colors regularly. is there a scientific basis for this or is it some kind of new age thing? i know you get different types of nutrients from different vegetables, but would i get the same from carrots and squash because they're both orange? what about bell peppers, should i pay extra to get yellow and red ones to go with the green?
Veg of different colours would at least imply a variety of vegetables, which would presumably provide a broader range of nutrients than eating one type only. Food stores often sell peppers in packs of red, yellow, and green. I've never noticed different prices for different coloured bell peppers, but some of the more specialized peppers may only come in one colour. Orange veg might have more beta-carrotinoids in them, ~ I dunno if that's universal to _all_ orange veg. I think the main point is to eat a variety.
The Oregon State (USA) Beach Bill (House Bill 1601, 1967) established public ownership of land along the Oregon Coast from the ocean up to sixteen vertical feet above the low tide mark. But establishing the low tide mark was tricky and in the southern areas of the state were the beach land is very flat meant that hundreds of feet of beach land could be public or private depending on just where "low tide mark" was. Officials finally worked out a complicated definition of "low tide mark". I am not sure what that definition is. I assume that it was finally tied to an officially recognized vertical datum. I do not know if there will be a new definition of "low tide mark" as sea levels rise.
The reason why you want to know the sea level depends on whos asking. Like if you want to launch a space craft what you really care about is thickness of the atmosphere and how far up you need to go. Sometimes its good enough just as an arbitrary point for zoning.
I remember being introduced to the "Metric" system during my elementary years during the 70's. Now the last half decade there is a big push in the US to finally make the change.
Tyvern Overlord eh, actually radio waves are part of the electromagnetic spectrum. Visible light is just a very small portion of that spectrum. So he’s not wrong. Just like infrared or ultraviolet light is still light, even though it’s outside of what humans are able to see.
Well it's easy for him at 976 metres above sea level to talk calmly about rising sea levels but I live in England at the lofty height of 79 metres above sea level and so I'm a bit more worried. Then again I used to live in London at 0 metres above sea level so I suppose I have to be grateful for what I can get.
As a pilot, this makes me question my every day use of ASL. It's simple enough to say CYGM is 753 feet asl give or take maybe 5 feet or CFK6 (my local gliding center) is 3330 feet asl, but I never really stopped to think about what asl means. I just set the altimeter during the checks and forgot about it.
I understand that the earth is warming and that is always discussed in a negative context (not saying I'm pro-warming)but the earth has warmed before (albeit naturally). Objectively speaking, what is the ideal temperature trend supposed to be? Is it better if the earth warms, or is it better if the earth cools? Obviously, climate changes periodically, but I wonder which is best for human life.
As a Land Surveyor in Alberta, Canada, this is quite interesting. I wonder how it's determined for us... and does this mean that ASCM's have to be constantly updated???
No: having a consistent frame of reference is more important than being up-to-the-minute accurate. (Fun fact: continental drift is also moving us SW-ish.)
Seems to me that tidal gauges are more accurate, because they can be shielded from waves. The satellites should be used to measure how much the land moves and adjust the tidal gauge data. Satellites have to measure millimeters from 250+ miles up, dealing with waves and gravity (as the video explains).
Chad Purser Except Satellite data is extremely accurate and reliable. And-more importantly- it attempts to give us the answer to the question we care about. “Global sea level averages and trends”. As you might have noticed tide gauges are only *local* and therefore any individual station can only tell you sea level proximity. To get a larger picture you NEED to stitch together a multitude of the most reliable tide gauge stations around the world, and then you have to adjust the data to account for a host of factors that could corrupt the data. Like ground movement(glacial isostatic rebound, local subsidence and continental crust), planets crustal gravitational anomalies, moon& solar influences..., lack of global benchmark or datum to facilitate stitching. Some of the stuff they talked about in this video. And *even then* you *still* have the problem of tide stations not being equivalently spread around the world, but are biased towards populated developed costal regions. There a lot of hole that need to be accounted for in the data. It’s hard work using tide gauges to get an accurate picture but if you want answers I do have excellent links to peer reviewed scientific research that goes in the trouble of doing just that: www.glaciology.net/pdf/jevrejeva-gloplacha13-virtual-station-recon-w-gia.pdf -“extend the reconstruction There is a good agreement between the rate of sea level rise ( 3 . 2 + 0 . 4 mm . yr - 1 ) calculated from satellite altimetry and the rate of 3 . 1 + 0 . 6 mm . yr - from tide gauge based reconstruction for the overlapping time period ( 1993 - 2009 ).”
"Radar works by timing how long light takes to bounce off a target." No, this is a lie. It works by modulated signal phase comparison. The timing thing is a lie because technical things are way too complicated for simple folk.
@@piteoswaldo I can live with that because it's all the same type of energy, just different frequencies bands of electromagnetic radiation. These bands are a human conceptual convention, not an absolute truth. en.wikipedia.org/wiki/Electromagnetic_spectrum
So.... what I got out of this is that we've got a new way to see if there's intelligent life in the universe, by checking if they've changed their climate enough to affect their planet's orbit in a relatively short amount of time xD
You convinced me. I'm returning my sea level back to the store. It wasn't very useful anyway.
Did you typo, i think you meant Shore 🤣
Spirit levels on the other hand... Gah, ectoplasm.
Feels
Do it quickly. There is a 30 days money back guarantee
I'm still in the store, it's been an hour since I asked an attendant for the 'Long Weight' my work buddies sent me in for.....
This is the best Sci-Show video I've seen in a while.
It's very informative for me, as I live 6' above sea level. On top of that, I live about 400' from a tidal bayou canal.
The last big storm pushed the sea water up into the bayou, where it was opposed by the rainwater draining out. For about 9 hours it was inches from having overflowing sea water gushing through my neighborhood. Then it finally started to recede. I worry that next time we won't be so lucky.
It sounds as though you're six feet above sea level, only because you're six feet tall.
I live in the Netherlands, half my country is below sealevel
@@christafranken9170 Sounds like Atlantis
I live in a similar area. There are still many dead trees, not yet cleared away for some reason, killed by the salt water during the storm-caused flooding on the coast (from Hurricane Katrina). Our city, though it is almost 100 miles inland, is only fifty feet above sea level, if I recall correctly. And before Katrina, people in our town really believed that no storm would ever really damage US. Now, everyone's afraid just the same as you've said. Anyone actually on the coast (or, gods defend them, in New Orleans) has to be living in a state of constant worry.
@@Beryllahawk Grew up in Lafayette and enjoyed swimming down our street multiple times every year. The even more pissed off than normal moccasins weren't fun, though.
Measuring the Sea Level is hard, because the Sea isn't Level
🤯
I sea what you did there.
yes you can because the world is flat
@@kaiptanof you live in a different reality then probably
I'll have you know the sea is not hard, it's really wet and swishy.
I feel like there's a vsauce video here "how much would the sea level rise if we all walked into the sea?"
@@AxxLAfriku go watch Vsauce, those videos need a couple million views more.
Less than currently expected.
Below 10 billion humans below 500kg (likely below 100, given the starving children to be included) on average at hardly higher density as water/hardly lower volume could only lead to 5 000 billion L additional volume, that's 5 000 000million cubic meters so 5 000 000 000 000 km3?
I think big numbers need sleep now or paper to be computed on 😅
@@fionafiona1146 question is how much would it rise, not how much volume it'd add. answer is likely an insignificant amount which wouldn't even be measurable anyway
@@xnirvanaXnevermindx
Didn't my first stancer imply I only entertain the idea as a joke?
vsauce is a terrible youtube channel that tries to make simple questions sound mysterious and mind boggling.
It's hard to measure because the excess water keeps falling off the edge of the Earth.
Sebastian Elytron good one
An NBA player me thinks!
Well! Now we know where to put the turbines, eh?
😑
It’s getting harder to measure because the ice wall is melting
Easy. Sea level is equal to 0m (0ft) above sea level.
Oh, that Sea level!
Sir, you are a genius
NASA wants to know your location
And also 0m below sea level
I appreciate that you stated both metric and imperial, would have been confused otherwise
Before video: "okay, complicated. But not thaaat complicated."
After video: "...oh."
Am from Finland. While exploring forest, found a neglected sea marker in middle of the forest about a half a kilometer from the current ocean shore. Thought, well, let's just swiftly move on, this stuff just is here nowadays.
Oh, no. Dude. You have to show it to someone else, or you have a week to live!
@@montycantsin8861 According to Swedish alarmists it's 13 years, and a few dingy Congresspeople, which are all crap arguing over who is less shite, but forgetting to remove their sponser tag lines.
Sooo sea levels down then?
@@buddyguy4723 as the video says, sea levels are dropping in Baltic Sea because of the post-ice-age rebound. If you have zillion tons of ice dumped on you, you shouldn't be surprised if the very ground gets pushed down and it takes tens of thousands of years to get back up!
@@Steevo69 the heck are you talking about. The Swedes can go to the beach and say "yep, the sea is definitely receding. But that has nothing to do with anthropogenic climate change, because there's obviously no continental ice shelf here anymore. Clearly the work of post-ice-age glacial rebound. Ice goes away, ground goes up, makes sense."
Good use-case for the Dunning-Kruger effect. Nature is far more complex than even reasonably knowledgeable people realise. That is why climate change is so dangerous to politicize.
HOW DARE YOU
"sea level means what we need it to mean"
_conspiracy theorists will remember that_
Mis*remember it, like everything 😆
Quote miners gonna mine.
Fudge, this is one of the best sci shows I've seen in a while! I mean they're all good, but this one really got the hamster wheel of my mind rolling!
Person A: I need directions, where exactly are you located?
Person B: I'm 976 meters above sea level, good luck finding me.
I just wanna know if I have to cook my burrito longer or not, geez...
Lmao! Exactly!
That actually depends more on barometric pressure, which you can measure without having to know where sea level is. Pressure just gets lower with altitude, but there's no exact figure that says for example, 95kPa means you're so far above sea level, since wather and presumably tidal forces and gravity will also make it change. But it's easier to measure than sea level, all you need is a barometer. Yes yes, I know I missed the joke, but nevermind that and go build yourself a barometer so you can cook your burrito.
@@VoidHalo and now I am going to get a barometer for my kitchen!
Does anyone know what the triple point of a burrito is?
I could feel the fluid dynamics derived pain throughout the video.
Fluid dynamics is a tough cookie.
Marin3r yes, the sea level problem is much more complicated than I realized, yet people talk about it all the time as if it were a simple computation.
Tough yet malleable...
Stephen Powdexter Stick a measuring stick into the sea. Boom
Marin3r, And when that cookie crumbles.....
4:20 -- "For instance, sea level is rising 3mm on average." 3mm per year? Per month? Per decade? I think a time component is missing in there.
Sea level is measured each time it rises 3mm. That's why it's always on average
@@brinx8634 And of course the scientists who perform the measurements know when there had been a 3mm rise and that a new measurement is needed. Makes perfect sense
per year, globally, as measured by satellite data: climate.nasa.gov/vital-signs/sea-level/
3mm (best estimate) per year, at a linear rate for the past several hundred years, since the exponential rate that tapered off after the last ice age.
3/10 of a centimeter is huge oh wait no it is not
Kinda surprised there was no mention of thermal expansion of water. Warmer water = more of it.
orange-micro-fiber
He did mention how weather affects sea levels, and temperature is an important part of that.
Nillie i disagree. Thermal expansion of water would almost definitely be categorized as climate issue, not weather. He was probably talking about precipitation and evaporation when he said weather.
WhatsUpEarth
Then it falls under the climate change section later in the video.
@@ragnkja I agree with you, but you're forgetting the rules governing climate change discussion. The climate alarmists insist that climate and weather be covered separately. Unless, of course, if local weather seems to support their position, then it's considered valid evidence. If local weather seems to refute man made climate change, that is not allowed to be used as evidence.
@@tomjacobson7623 I've observed exactly the opposite. We've had some hot summers lately and every time the scientist are asked if that has something to do with climate change they say you can't see that in isolation. On the other hand americans have pointed out to me they had a cold winter. I've never heard any climate denier sound remotely scientific. Mostly, they sound like it's a like what football team you support.
I knew deciding on "sea level" was non-trivial, but I was just thinking about tides. I hadn't considered what gravitational anomalies would do
Good job on covering that so well in less than 6 minutes :)
I just want to pause, appreciate and thank SciShow for consistently using the metric system and not bothering me (and all the other international viewers) with Miles, Feet, Ounces, Fahrenheit and what not.
I'd like to hear more about ice, gravity and the Earth's spin.
Sounds quite interesting, if complicated.
Hard to believe a satellite's orbit is that accurate.
It’s not. It’s the clock they use to time the return signal that needs to be good. Given the speed of light is so fast the satellite is essentially stationary over a send and receive.
Satellite orbits are in a constant state of flux; Therefore, their altitude is changing, making any calculations based on RADAR/LIDAR measurements more complex.
Spring and neap tide sections of science classes made me a lunatic.
Well, you're smarter than most.......you know what a neap tide is. IT'S SCIENCE! I luv ya Limey.
I came to write, what a great video this is; well explained, covers all the bases, clear, uncomplicated (Yes, I know it's complicated but .. ) and accessible. Scrolled down through the comments and it seems, I'm not alone. Well done SciShow, and eminently well spoken Stefan, you're definitely the best presenter for this. Kudos all round.
CONCLUSION: It is impossible to measure sea level and thus impossible to claim that sea levels are rising.
Measuring coastlines is also a complicated undertaking. The measurement can be infinite since the more you zoom in the more you see details like coves and inlets.
Love to see a video about how much of the world's ice (glacier, polar ice caps) have melted since 1970 and how it has effected the planet to date.
When we were sailing in Portugal, the tide was 14 feet. Then we sailed into the Mediterranean and there is no tide at all!
Sea levels are crazy!
Definition of Height Above Sea Level:
"How much the oceans have to rise before you need your boots."
What kind of weirdo walks into the sea in boots? Just take off your shoes
@@limiv5272Excuse me, my point is you are NOT in the ocean, you are ABOVE sea level - which is why that # tells you how much it would have to rise before you ARE in the ocean and in need of boots! What kind of weirdo walks face-first into a cream pie like you just did? Just take off your google-glasses. :-)
You know what this video is missing? An explanation on how we actually set 0 for sea level.
He answered that. It is the mean of many measurements made over time... like at least a decade!
I can think of several reasons. Tides, storms, gravity variations, wind patterns, jet streams, ocean currents, the sun, tectonic activity, Glacial activity, and global warming.
Yeah
"If all of Greenland's ice melted sea level would actually drop by a could of dozen meters in Iceland." A couple of dozen meters? Like 24m or 78 feet? Like many times the effect of the sun or moon? Because of the effect of the gravitational pull of the ice? Is this number correct? Sounds a bit off to me.
It could be accurate, remember that the effect of gravity is inversely related by the square of the distance between the masses. The moon is far but the glaciers are very close.
I too found that effect size surprising. I wonder if a simplified model could help: Approximate the ocean around Greenland as infinitely wide, deep, and flat, and the ice sheet as a cylindrical disk hovering just above it, with a diameter of, say, 1,500 km, and height 2 km, and the density of water. Gravity from the ice sheet will perturb the surrounding sea surface into a meniscus-like shape. The question is what height that curve has as function of distance. We'd have to trace the gravitational potential at sea level from infinity inwards. Alas, going further needs more thinking than I can muster right now.
@@sternmg Yes, like the thinking. I was pondering more like a point mass for the earth and a point mass for the ice sheet. Some nicely rounded numbers: Mass of earth 6E24Kg, Mass of Greenland Icesheet 3E18Kg (Changing rapidly!) Radius of Earth 6000Km, distance from Greenland to Iceland 1200Km. This makes the earth only two million times the mass of the icesheet (which is pretty impressive for the icesheet itself).
If I'm thinking about it right that moves the center of mass one half of one 2000000 of the 6000000m radius towards greenland or 1.5meters. Making the sealevel 1.5meters higher than it would otherwise be (not 24m). What have I missed?
That sounds off to me too. Possible, but it does sound off. I really don't want to run the math though. I break things when I try to do math.
At 1:03 I thought he meant tides as tall as half the moon. That would be a huge wave
The solution is easy: if the Sun and moon is affecting the sea level, remove them and measure then set that as the Level. Put the Sun and moon back. What's the complication here?
I am glad you said to put the sun and moon back. I like them 🤣
This was an excellent video, lots of great information and it points out just how complicated the subject matter is, well done! Despite the silly comments some people post.
Thank you so much!! Doing all the research on sea level on my own as a laymen was very difficult and I made slow progress after weeks. This video was very helpful for my understanding of sea level and Climate Change. It has given me new crucial information and confirmed some conclusions I’ve reached on my research. It has equipped me better for Climate Change debates.
I learned that thing about the glaciers just yesterday from How To by Randall Munroe p.25. It really did surprise me (both the fact itself and that I heard the same fact two days in a row from two totally unrelated sources).
We're going to need a bigger straw!
RADAR with light is LIDAR, though RADAR is just SONAR with radio...
Slack's Shack radio waves are still electromagnetic waves
Radio and light are two aspects of the same thing. Sound is something else entirely.
Very good point, thanks for the correction! :)
Thanks for the show. Can u also explain what is the difference among AMSL, MSL, ASL?
The Earth : "Hey who you callin' Lumpy?"
Futurama put a giant ice cube in the ocean, let's just put a moon in the middle of the Pacific to attract all the water there
Scientists: let's measure the sea level!
The Universe: No
I've always wondered about big cities like NYC. How many tons of material are on top of Manhattan that weren't there a few hundred years ago, and what impact does that have? Is the tide higher because of the pull of the gravity from all the buildings? Is there enough man made/placed mass anywhere on Earth that would impact the Earth's rotation?
I usually think, no, because of the total mass of the Earth compared to the mass of those buildings. But I do wonder about it.
If something the size of a glacier can have a gravitational effect I imagine that a full city of metal would. I'd imagine it wouldn't have as much effect as a glacier because that's solid ice vs. All of the air and other low density materials inside of cities.
i do wonder the same thing but i would like to add i think it even more detailed then that cause not only is that spot getting "heavier" but the material used there came from somewhere so maybe making that spot "lighter "
You may think of cities as lots of building materials being brought _in,_
but a lot of excavated dirt is also _removed,_ eg basements and subways etc.
China's Three Gorges dam backed up enough water that Earth's angular momentum was changed, like a spinning skater pulling in their arms.
Earth's day length changed(!)
Slightly.
Bet there's a lot of Dutch people laughing at this video.
so if the ice caps melt nearby sea level will drop while further away it will go up. i wonder if the netherlands is north enough to benefit from this.
@@MusicalRaichu It is not, unfortunately.
Yep, Scandinavia goes up. We go down. This is not the most significant factor though.
Best video in awhile so much science took me for several turns and the next was always better than the last!
Can we not just state how much something is from the center of the earth? Like "I'm 6371 km from the center"?
I can think of a couple reasons: how do you find the center? The same things that affect sea level also make the center of gravity shift. And Earth isn't a perfect sphere, so how do you define the center? Also, you'd need more digits, like 6371 km might mean ±1 km, but when siting your house near the shore, you may need accuracy to the meter. 🤓
There is no true center of the earth. Even the Greenwich meridian changes depending on which map system is used. This is because the earth isn't a perfect sphere.
@@Tibovl It does have a centre of mass, though, which I think is what GPS is referenced to (latitude/longitude is a conversion from its native 3D Cartesian).
I could’ve watched another 10 minutes of this, at least! Need more! Thank you 🙏
Stefan, just a little nitpick here. You are describing LIDAR, not RADAR.
Absolutely love your presentation of information. Keep it up!
I've always felt like a drop in the bucket. Thanks.
SciShow--can you please do a video on the Australian bushfires--ex. how they got started; what has been the impact on wildlife? And speculate on the short and long term impact these massive bushfires will have on our environment.
This was _very_ informative! Great video!
100 meters water level difference caused by local gravitational anomalies? That sounds insane.
This was a really great episode, thank you
Inglés
I just wanted to watch a easy video before going to sleep and then my mind exploded, love you guys.
2:40 "RADAR works by timing how long light takes to bounce off a target"
Don't you mean radio waves, or LIDAR?
[Pedant] Radio waves are light. [/pedant]
@@dongiovanni4331 No, radio waves and light are specific types of EM radiation, but they're not the same
RADAR uses Radio, LIDAR uses Laser
Replace "light" with "electromagnetic radiation"
All good?
This episode is great to remind us that many (relatively simple) laws of physics will give a very complex outcome on the whole.
I was wondering about what sea level means just yesterday. Thanks for reading my mind, SciShow!
Sea level is also affected by salinity and temperature, which change the density of water. There's a difference of 20 cm between the north side of Panama and the south side.
Because of such variations, surveyors now reference elevations to the geoid, a theoretical equipotential surface that is close to sea level.
But you didn’t mention anything about how you know your so many meters above sea level and what that is... what is 0??
The satellites with the radars would measure the distance from the sea level; if it takes, say, 10 seconds for the signal to bounce back from the sea level and then you shoot the ray at land and it takes 9 seconds, you know the terrain is 1 second above sea level (which you would then convert into meters based on how fast the ray is traveling).
As for your second question, I don’t know, but I assume that they defined X elevation as ‘sea level 0’ (based on averages or what ever) and basically ignore the raising/lowering of the actual sea after that point.
Someone more knowledgeable than me may have a better answer for this, though.
Andrei Tache but what is 0? Or the standard point? How high is sea level? Is it 22 miles below the aptomsphere edge? Is it 33 miles? What’s the point of standard??
_”In the UK, the Ordnance Datum (the 0 metres height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921.” (__en.wikipedia.org/wiki/Sea_level__ )_
That’s about as good of an answer as I could find after a short google search. There really isn’t some fixed point around which to anchor our measurements (even the atmospheric edge isn’t a perfect sphere, thanks to the earth’s squished proportions and terrain deformations like mountains..)
If you find some more complete answer, let me know
Generally, those measurements assume a datum, or reference standard, that they are measuring against.
Randy Allen you can not assume a standard. The very term is an oxymoron!! A gram is the gram. The meter is a meter and so forth.
The most meaningful episode so far!
1:19
but wikipedia says we have lunar eclipse 2-5 times a year... so can't be that they align once every 19 years...
did i misunderstand something?
btw, I love these videos. I watch every single one, thanks for the endless (yet useful) 5-minute breaks everyday!
He was talking about aligning perfectly, a lunar eclipse only needs us to block the sun partially
They're saying the lowest common denominator of lunar cycles and solar cycles is 19 years, as they're of different lengths. Still not a big deal, if you know a little physics.
@@DarkAvador ah right, got it. thanks!
I live near a famous stadium in London and my house is supposed to be 41 metres above sea level. Geographically I'm living on the steeper side of a very large river valley.
I live in Israel, we have a region of land that's BELOW sea level. Yes, people live there
@@limiv5272 Just like island nations like Tuvalu and of course the Netherlands, if the absolute worst happened most capital cities of the world would disappear, as would vunerable places like the above mentioned, hopefully we can stop that happening.
@@julianaylor4351 Actually the area I mentioned is separated from the sea by some mountains, so I think it's in much less danger than island nations
Finally someone who mentions that sea level isn't flat because gravitational anomalies. If I'm not mistaken, the lowest sea level due to gravity is in the Indian Ocean. It's about a 100m lower than the average height.
You wouldn't notice it but if you sailed across an ocean you would sail up and down hills of water.
*_...and as the Earth loses thermal energy, and shrinks, (nearly-maintaining its temperature, from extracted gravitational energy), its surface area diminishes and its seawater volume height increases..._*
It was helpful
Very insightful 🌊, Great video 👍👍
Sea level based on satilites does seem to have absolutely nothing to do with real world sea levels though.. Which is important to remember whenever Greta or someone talks about the abocalyps
I read this as “sea elves” rather than sea levels and was excited for a minute
I'm always willing to learn more about the Teleri.
The Earth is shaped like a Boglin.
Measure a drop of water, then count the drops of water in the ocean.
That would be hard. You would need to make a new pile of water drops, so you don't mix them up with the ones you haven't counted yet.
You have to get a whole, other earth to put them on.
@@montycantsin8861 Uhhh, I think he/she was joking...
@@souhiyori8640 uhhm, I think I was too. It's called "riffing".
@@souhiyori8640 unless you believe that I think you can make a "pile of water drops".
@@montycantsin8861 You can if you freeze the drops first.
just thought of something, warm air can hold more water, so a warmer climate would actualy drop the sealevel? you know once all the ice is gone.
so weird.
You need to also keep in mind that warmer water expands in and of itself.
@@d4mdcykey I thought it was the other way around for water, it expands when frozen, shrinks when warmed. It's one of the only substances that act like this, very unusual.
@@dreggory82 ~ Nah, you're confusing ice with liquid, two different things. Heated water (liquid) expands, it's called Thermal Expansion: sealevel.nasa.gov/understanding-sea-level/global-sea-level/thermal-expansion
@@dreggory82 As temperature up goes down, water expands and contracts like most things, except when it drops below 4 C. As temperature lowers past 4, water starts expanding again and eventually ice ends up less dense than water.
What's missing from this discussion is how much (or little) each of those different factors affect the measurement. I.e. as an example, Lunar tides might affect 90 percent (guessing) of the measurement, and gravitational anomalies only affect 0.01 percent, than you only need to worry about these different factors if you need a precision of millimeters.
also, i been asking this, perhaps i'll do better on a new video, but does it make a difference what color vegetables you eat? i've heard you should eat vegetables of different colors regularly. is there a scientific basis for this or is it some kind of new age thing? i know you get different types of nutrients from different vegetables, but would i get the same from carrots and squash because they're both orange? what about bell peppers, should i pay extra to get yellow and red ones to go with the green?
Veg of different colours would at least imply a variety of vegetables, which would presumably provide a broader range of nutrients than eating one type only.
Food stores often sell peppers in packs of red, yellow, and green. I've never noticed different prices for different coloured bell peppers, but some of the more specialized peppers may only come in one colour.
Orange veg might have more beta-carrotinoids in them, ~ I dunno if that's universal to _all_ orange veg.
I think the main point is to eat a variety.
The Oregon State (USA) Beach Bill (House Bill 1601, 1967) established public ownership of land along the Oregon Coast from the ocean up to sixteen vertical feet above the low tide mark. But establishing the low tide mark was tricky and in the southern areas of the state were the beach land is very flat meant that hundreds of feet of beach land could be public or private depending on just where "low tide mark" was. Officials finally worked out a complicated definition of "low tide mark". I am not sure what that definition is. I assume that it was finally tied to an officially recognized vertical datum. I do not know if there will be a new definition of "low tide mark" as sea levels rise.
Thanks for making this video.
The reason why you want to know the sea level depends on whos asking. Like if you want to launch a space craft what you really care about is thickness of the atmosphere and how far up you need to go. Sometimes its good enough just as an arbitrary point for zoning.
I'm absolutely delighted to learn about this. :-D
I remember being introduced to the "Metric" system during my elementary years during the 70's. Now the last half decade there is a big push in the US to finally make the change.
Canada: Thanks, that's really great to hear.
USA: When I want your opinion I'll tell you it first!
Canada: Terrific - sorry and thanks again.
Also submarine ground formations (such as plains, mountains, valleys, etc) affect sea level as well.
Or as said in the video, the earth is lumpy.
So good I watched it twice!
using light would be LIDAR wouldn't it? RADAR is Radio wave.
lol good one, Radar is light.
LiDAR and LaDAR are light
RADAR is radio
james Moore
No, no it most certainly not
Tyvern Overlord eh, actually radio waves are part of the electromagnetic spectrum. Visible light is just a very small portion of that spectrum. So he’s not wrong. Just like infrared or ultraviolet light is still light, even though it’s outside of what humans are able to see.
Nice white & gold shirt you got there,
would be a shame if someone mistaking it with a blue & black.
Ridiculously fascinating
The consistency of inconstancy. Sounds consistent to me.
Well done
Well it's easy for him at 976 metres above sea level to talk calmly about rising sea levels but I live in England at the lofty height of 79 metres above sea level and so I'm a bit more worried. Then again I used to live in London at 0 metres above sea level so I suppose I have to be grateful for what I can get.
@Kali Southpaw Yes, but fortunately I live in an apartment above a shop, so I get an extra 3 metres or so. Phew!
As a pilot, this makes me question my every day use of ASL. It's simple enough to say CYGM is 753 feet asl give or take maybe 5 feet or CFK6 (my local gliding center) is 3330 feet asl, but I never really stopped to think about what asl means. I just set the altimeter during the checks and forgot about it.
Earth spinning happily. humans; Hold my damn beer, builds mega dams, and melts the glaciers.
Tide goes in, tide goes out, never a miscommunication.
You're welcome, this show brought that screeching back into my mind.
Tides go in, tides go out, you can't explain that.
The Panama canal connects two large seas which are both at sea level, yet it still requires locks because the water levels are different.
So that angry teenager Greta could be wrong? Sea levels are rising because the earth is still rebounding from a previous ice age?
Global sea levels, no.
Local sea levels, yes.
I understand that the earth is warming and that is always discussed in a negative context (not saying I'm pro-warming)but the earth has warmed before (albeit naturally). Objectively speaking, what is the ideal temperature trend supposed to be? Is it better if the earth warms, or is it better if the earth cools? Obviously, climate changes periodically, but I wonder which is best for human life.
As a Land Surveyor in Alberta, Canada, this is quite interesting. I wonder how it's determined for us... and does this mean that ASCM's have to be constantly updated???
No: having a consistent frame of reference is more important than being up-to-the-minute accurate. (Fun fact: continental drift is also moving us SW-ish.)
Love this
Seems to me that tidal gauges are more accurate, because they can be shielded from waves. The satellites should be used to measure how much the land moves and adjust the tidal gauge data. Satellites have to measure millimeters from 250+ miles up, dealing with waves and gravity (as the video explains).
Chad Purser Except Satellite data is extremely accurate and reliable. And-more importantly- it attempts to give us the answer to the question we care about. “Global sea level averages and trends”. As you might have noticed tide gauges are only *local* and therefore any individual station can only tell you sea level proximity.
To get a larger picture you NEED to stitch together a multitude of the most reliable tide gauge stations around the world, and then you have to adjust the data to account for a host of factors that could corrupt the data. Like ground movement(glacial isostatic rebound, local subsidence and continental crust), planets crustal gravitational anomalies, moon& solar influences..., lack of global benchmark or datum to facilitate stitching. Some of the stuff they talked about in this video.
And *even then* you *still* have the problem of tide stations not being equivalently spread around the world, but are biased towards populated developed costal regions. There a lot of hole that need to be accounted for in the data.
It’s hard work using tide gauges to get an accurate picture but if you want answers I do have excellent links to peer reviewed scientific research that goes in the trouble of doing just that: www.glaciology.net/pdf/jevrejeva-gloplacha13-virtual-station-recon-w-gia.pdf
-“extend the reconstruction There is a good agreement between the rate of sea level rise ( 3 . 2 + 0 . 4 mm . yr - 1 ) calculated from satellite altimetry and the rate of 3 . 1 + 0 . 6 mm . yr - from tide gauge based reconstruction for the overlapping time period ( 1993 - 2009 ).”
I guess Steven Wright would say about this: It doesn't matter what the height of the sea is, it's aways sea level.
"Radar works by timing how long light takes to bounce off a target." No, this is a lie. It works by modulated signal phase comparison. The timing thing is a lie because technical things are way too complicated for simple folk.
Also, radar uses radio waves, not light.
@@piteoswaldo I can live with that because it's all the same type of energy, just different frequencies bands of electromagnetic radiation. These bands are a human conceptual convention, not an absolute truth.
en.wikipedia.org/wiki/Electromagnetic_spectrum
So.... what I got out of this is that we've got a new way to see if there's intelligent life in the universe, by checking if they've changed their climate enough to affect their planet's orbit in a relatively short amount of time xD