"The IPCC predicted global temperature increases of 1.8 to 4 degrees Celsius (3.2 to 7.1 degrees Fahrenheit) by 2100 and sea levels to rise between 7 and 23 inches (18 and 58 centimeters) by the end of the century. ...
"'An additional 3.9-7.8 inches (10-20 centimeters) are possible if recent, surprising melting of polar ice sheets continues,' the report stated." (From CNN)
Talk about the danger of rising sea levels, at least in my experience, is usually accompanied by verbal images of Florida flooding, Manhattan and London under water, and similar catastrophes. If the IPCC figures are correct, the upper end of the range of what might actually happen is a rise of less than a meter over a century--considerably less than the distance between high tide and low. Popular talk about global warming, again in my experience, is usually put in terms quite a bit more apocalyptic than the IPCC's upper estimate of four degrees Celsius by 2100.
So far the only report I have seen is on CNN, but I will be pleasantly surprised if any newspaper headlines the story with "Global Warming a Wet Firecracker? International Panel finds temperature and sea level effects over the next century real but small."
"'An additional 3.9-7.8 inches (10-20 centimeters) are possible if recent, surprising melting of polar ice sheets continues,' the report stated." (From CNN)
Talk about the danger of rising sea levels, at least in my experience, is usually accompanied by verbal images of Florida flooding, Manhattan and London under water, and similar catastrophes. If the IPCC figures are correct, the upper end of the range of what might actually happen is a rise of less than a meter over a century--considerably less than the distance between high tide and low. Popular talk about global warming, again in my experience, is usually put in terms quite a bit more apocalyptic than the IPCC's upper estimate of four degrees Celsius by 2100.
So far the only report I have seen is on CNN, but I will be pleasantly surprised if any newspaper headlines the story with "Global Warming a Wet Firecracker? International Panel finds temperature and sea level effects over the next century real but small."
27 comments:
These are average figures for the world. You should not deduce from them that what will happen is just what we have today with everything shifted up 60 cm. The important figure is changes in sea level extremes, if you want to assess this with any common sense attitude. If sea level extreme were to rise only by 60 cm, I agree, no problem at all. But to say that sea level rise is no problem because 60 cm is not much does not make any sense if you don't know the changes in extremes.
This seems a classical case of the problems that arise when one expert group (climate scientists) hands of data to another (economists). Everyone in the climate group would know that it does not make any sense to conclude that a 60 cm rise in average sea levels can be assessed by saying "oh, it is only up to my knees then", which is a bit what you seem to imply :)
From looking briefly at the IPPC report released today, they don't talk about regional sea level rise, or changes in extremes or anyhting. I guess that will come out of working group II, but don't really know.
"These are average figures for the world. You should not deduce from them that what will happen is just what we have today with everything shifted up 60 cm. The important figure is changes in sea level extremes, if you want to assess this with any common sense attitude."
Why would you expect the extremes to change by more than that? The sea level rise is partly a result of expansion due to a slight temperature increase, partly a result of melting of ice currently on land and so not currently displacing water. Both effects result in increasing the total volume.
All of the world's major seas are linked, so I don't see why a very slow increase in volume would raise levels in one place more than another.
"This seems a classical case of the problems that arise when one expert group (climate scientists) hands of data to another (economists)."
In this particular case I'm responding as a physicist not as an economist. Climate is a physically complicated question; I can easily imagine that the predicted change in average world temperatures might be unevenly distributed either geographically or temporally, and so might change extremes in some places by much more than the average. But the level of a fluid in a group of connected chambers is a much simpler problem, solved long ago.
Am I missing something, and if so what?
David, you seem to be misunderstanding the term. The extremes are due to tides, storm surges, waves, and other effects.
Extremes are non-linear in their effects: consider the effect of a recent extreme in New Orleans.
It is also expected that extremes will change in magnitude and frequency due to global warming,
That would seem, then, a different thing from sea-level rise. If hurricanes are more intense and storm surges are therefore bigger, that's in addition to (and entirely separable from) a rise in sea level. That may make it less of a "wet firecracker", but it doesn't seem to be related to the passage cited here.
Global warming will not change the size of the tides; high tide will be elevated by the same amount as sea-level.
"This seems a classical case of the problems that arise when one expert group (climate scientists) hands of data to another (economists)."
Are there any problems that arise when climate scientists pretend they're economists?
"Global warming will not change the size of the tides; high tide will be elevated by the same amount as sea-level."
I think that's close enough to true for practical purposes, but not precisely correct. What drives the tides is the gravity and orbital motion of the earth/moon system, which isn't going to be changed by global warming. But the earth is not entirely ocean, so the detailed pattern of local tides is also affected by the ways in which moving seawater is constrained by the land barriers.
I wouldn't expect sea level rises of the small magnitude being predicted to change that much. Insofar as they did, I would expect them to reduce variability, not increase it, since the deeper the ocean is the less the land blocks its movements.
Perhaps Mike can explain why he draws the opposite conclusion.
"You may not have noticed but this week's UN report on global climate change based its estimate of a 1- to 2-foot rise in sea levels over the next 100 years on computer modeling which took into account only the volumetric increase in sea water as it warms. The estimate for sea level rise did not include melting glaciers and icecaps. While this was duly noted in most of the coverage I saw, it was often buried. The WSJ has a piece today on how much more dire the effects of climate change may be if you consider melting ice and increased cloud cover, neither of which factors the current computer models handle very well."
From Talking Points Memo; the WSJ piece is here.
Jim quotes a source as saying:
"You may not have noticed but this week's UN report on global climate change based its estimate of a 1- to 2-foot rise in sea levels over the next 100 years on computer modeling which took into account only the volumetric increase in sea water as it warms. The estimate for sea level rise did not include melting glaciers and icecaps."
As you can see by looking at the quote at the beginning of my initial post, the IPCC included an estimate of the effect of possible melting of polar ice sheets--an additional 10-20 cm. That was included in my "less than a meter."
Note, by the way, that it's only the southern polar ice sheet that matters in this context. The North polar ice doesn't have any land supporting, so is already displacing its weight in sea water.
It would seem like the biggest risk is to Bangladesh, a heavily populated place that already suffers big death rates during sea surges. If, say, $10 billion worth of dikes could protect Bangladesh from rising sea levels, well, that's not a big price to pay.
Just follow the moeny trail on the agenda for who paid for the climate study. For one huge fraud read about DuPont, Gore and Freon.
Here are soem interesting sites to read. Bob M
Greenland ice melt would also be a problem, as the glaciers there are currently supported by land.
"I wouldn't expect sea level rises of the small magnitude being predicted to change that much. Insofar as they did, I would expect them to reduce variability, not increase it, since the deeper the ocean is the less the land blocks its movements."
Rising sea levels could greatly increase the rate of erosion of deltas and estuaries by allowing water to move over them. Think riptides where there are none now.
And if there is less impedance of ocean movements, waves reaching the shore can be larger.
Not to mention that it's expected that rising temperatures will create more and bigger tropical storms: that too will increase extrema.
But even if (on the average) the extrema are the same, they will be distributed differently, necessitating new protections for currently unprotected areas.
BTW, you're showing your lack of expertise again. The North polar ice is not an ice sheet. However, the Greenland ice sheet does matter: if it entirely melted, sea levels would rise an estimated 7.2 meters.
Are you sure you want to be on the side of the contrarian frauds currently being sought by the oil companies? Thank you for smoking.
Dr. Friedman, I love ya, but I'm pretty sure you just got told.
A commenter at Catallarchy, Grant Gould, had this to say regarding your comment about the northern ice:
"The northern ice sheet is a decent proxy for Greenland, though, which is the really big deal – unlike the antarctic it’s seen serious melts in recent geological history, and it has more than enough ice cover to make a big difference.
"My understanding is: It’s hard to measure ice cover over land, because the melting doesn’t necessarily happen near the surface – small amounts of surface melting change the pressure lower down, leading to chaotic effects that don’t show up at the surface until something cracks open. Ocean ice, because it is under varying forces, tends to react more quickly to changes and so is a better proxy than the available direct observations."
Several different points:
The Greenland ice is indeed supported by land and so can raise sea level if it melts; the ice at the north pole is not and cannot. The IPCC report which I quoted includes a figure for the effect of continued melting of ice sheets. While I suppose it is possible that they were for some reason including Antarctica but not Greenland in that calculation, it seems unlikely.
Going back to sea levels. Mike's claim about variability included tides, and that's the part that seems to me to be clearly wrong. Weather is complicated but tides are at least relatively simple.
It's possible that Mike agrees that he was wrong about the tides, but he hasn't yet said so. Insofar as "Rising sea levels could greatly increase the rate of erosion of deltas and estuaries by allowing water to move over them" that is yet another reason to expect decreased variability in tidal effects, for the reason I already mentioned.
I agree that changes in climate could lead to changes in weather patterns which could lead to higher (or lower) waves--but again, that isn't the sort of thing people are implying when they talk about drowning Florida and Manhattan.
So far as Katrina, New Orleans has been recognized as a catastrophe waiting to happen since long before global warming was an issue. When we lived there, more than twenty years ago, my geologist wife explained the two quite different ways in which a suitably placed hurricane could produce a disaster--and we bought a house that was several feet above sea level.
The catastrophe that hasn't happened yet is the one that lets the Mississippi shift its mouth, as it would have long ago were it not for the Army Corps of Engineers. That one drowns Morgan City and leaves New Orleans no longer a port. It doesn't require global warming or sea level rise either.
As to Mike's final comment, I'm sorry to see him going along with the widespread attempt to represent a probable problem as an almost certain global catastrophe, providing justification for practically anything proposed in the attempt to prevent it.
"Going back to sea levels. Mike's claim about variability included tides, and that's the part that seems to me to be clearly wrong. Weather is complicated but tides are at least relatively simple."
If we are talking about the highest tides now being 60 cm higher because of rising sea levels, then this does affect extremes and our responses to them. For example, dikes would need to be 60 cm higher. I didn't use the term variability: that's your word. Perhaps if you were careful to quote what you're rebutting....
"Insofar as "Rising sea levels could greatly increase the rate of erosion of deltas and estuaries by allowing water to move over them" that is yet another reason to expect decreased variability in tidal effects, for the reason I already mentioned."
Deltas and estuaries buffer tidal effects: they take significant time to fill and drain, hence the further from the open sea you travel, the smaller the tidal effect. Erode them away, and you are placing areas in direct proximity to the sea, and those areas will experience greater tidal effects.
"So far as Katrina, New Orleans has been recognized as a catastrophe waiting to happen since long before global warming was an issue."
You have missed my point, which is that changes in extremes could make these catastrophes happen sooner or with greater frequency.
"As to Mike's final comment, I'm sorry to see him going along with the widespread attempt to represent a probable problem as an almost certain global catastrophe, providing justification for practically anything proposed in the attempt to prevent it."
Sorry, David, propaganda is YOUR family business. I've been presenting rather credible scientific information to correct your errors and lack of understanding of the issues. If you are worried that people will misrepresent good science for a harmful cause, then the solution is to correct the misrepresentation or declaim against the cause: not to deny or trivialize the science.
David, I'm sorry: the above personal insult was a wretched thing to do.
I started along the line of the contrarian frauds (who are quite well documented) because it is very easy for honest skeptics like ourselves (with relativelty open minds) to be swayed on matters of fact by their subterfuges. I initially meant it as half warning, half playful twitting.
If you could edit out that family line, I'd be happy.
Are you sure you want to be on the side of the contrarian frauds currently being sought by the oil companies? Thank you for smoking.
You're not kidding, are you? Super.
Wow Mike.
I'll remember that line about David's family for a very, very long time. And such a short time after Milton's death too. Wow. Your credibility just took quite the hit!
To Mike:
On the question of tides I think we are both right, because we were talking about different sorts of variability. I was talking about how much the high tide/low tide difference varied from place to place. If that increases while the average stays the same, extremes get more extreme, which I thought was your point when you wrote:
"The extremes are due to tides ... It is also expected that extremes will change in magnitude and frequency due to global warming"
(snipping the stuff not about tides)
My point was that the point to point variation in the amount of tide would decrease rather than increase if sea levels rose, since it is due to the moving water being blocked by the land, less of which happens if the water gets higher.
You are correct, however, in what I think you are now saying and might have meant initially. There would be places where the high tide/low tide difference became more than it was in those places before, because rising sea levels meant that the water in those places was less isolated from the general movement of the tides than it used to be. That change increases tidal variation at that place, decreases tidal variation point to point, since that place is now more like the rest of the water of the planet-going up at high tide, down at low.
So far as your comment about my family, I don't think I can edit posts but I can delete them. You are welcome to repost your post with that comment removed and I will then delete (or you may if you can--I don't know if you can) the original. You might want to include a note about the existence of a bit you have now deleted, to explain to future readers why another poster was objecting to something that isn't there any more.
Finally, to summarize my views:
1. I was commenting on the IPCC report; no doubt there are other sources with more (or less) dire predictions.
2. According to that report, the upper limit of average sea level rise over the next 93 years, including the effects of both expansion due to warming and the melting of ice sheets, is 78 cm, less than a cm/year.
3. While a rise on that scale would pose problems for some low lying areas, it isn't a global catastrophe or anything close, especially given the very long time it is to happen over.
4. The same is true for the predicted temperature rise.
I offer no opinion on how serious other effects might be; I think everyone agrees that weather is still a complicated system that we can't model very well. But those two effects, which are the ones commonly cited and the ones for which we have the clearest evidence, do not come close to justifying the general tone of the current public debate over global warming. Simply taking those, the IPCC report should have been reported in the opposite of the way it was.
Finally, one point I don't think I made in the initial post. In my view, any prediction of that sort 93 years out should be viewed with great scepticism because the current rate of technological change makes future human acts and their effects, beyond the next few decades, radically uncertain. That's a general point that I explore in my Future Imperfect, webbed and linked to my site.
That is, they explicitly say that they are not able to provide an upper bound for sea level rise.
And you're going where with this, exactly? To my ears, it sounds like they don't know what they're doing.
Tim Lambert writes:
"That is, they explicitly say that they are not able to provide an upper bound for sea level rise."
Given the uncertainty, nobody can provide an upper limit, or for that matter a lower limit--note the "increase or decrease" in what you quoted--to possible sea level rise. The IPCC does, however, provide an upper limit to their estimates--the sea level rise that they think they have reason to predict. That estimate includes, as you point out, an allowance for melting of ice over both Antarctica and Greenland.
If I correctly interpret your quote and the quote I started my original post with, the .1 to .2 meter increase if melting increases above current rates is the additional 10 to 20 cm that I was already including in my 80 cm total.
If so, the CNN report actually made things sound a little worse than the IPCC. CNN said "if recent, surprising melting of polar ice sheets continue," but the actual condition seems to be not "continues" but "continues to increase."
In any case, thanks for the additional information.
David F.,
I hope you know the numbers for Greenland & Antartic meling are bogus on table SPM0 of the Summary ? They are 10x too big (the numbers don't add up). So I wonder if your stated 10 to 20 cm added sea rise takes into account this embarassing error from the IPCC or not.
Their estimates are usually 90% probability ranges. For ice sheet melting they are saying that too little is known to provide such an estimate. So numbers greater than 10-20cm aren't the usual 5% chance. News reports seem to have not covered this.
In addition, the IPCC indicates that an eventual rise 4-6m is likely, which is where those pictures come from.
I'm not sure New Orleans says much about anything to do with AGW. IIRC, Katrina was downgraded to a Cat 3, and most of the damage and the images in the public mind were a result of a complex set of bad engineering, corruption, and assurances and subsidies that encouraged too many people to live in an inherently dangerous area coupled with assurances that NOLA had and would properly execute an evacuation plan and that FEMA would do what it's name intended.
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What lies in the "apocalyptic" end of the probability scale is not covered in the IPCC average numbers that you quote.
Do we have to worry about that? Well, it depends on the chances that we end up in a situation where there is runaway climate change, with many positive feedbacks causing climate change to be more rapid rather than to stabilize it.
I don't know the numbers for this, but I would certainly be extremely concerned if there was say, a 1% chance of 2 meter sea level rise by the end of the century.
A 1 m sea level rise does indeed threaten large portions of Florida-- it'll wipe out barrier islands, removing the hurricane protection that thousands of coastal residents rely on.
Finally, calling this a "wet firecracker" ignores all of the other consequences of this sort of rapid climate change.
Even if we are to believe the chicken little prognosis that sea levels will rise, say by about 2 feet in 100 years, what really does that mean for us? It means we might have to build a sea wall two feet high, or two feet higher than now, or in fact, do nothing because existing sea walls have another two feet of unused cement remaining! The fact is that in 100 years, sea walls have to be replaced any way.
What happened in New Orleans is proof. That storm was only a category 3, but the levees were substandard and neglected. So they broke. New Orleans was not destroyed by the storm, it was destroyed by a sea wall that was defective, so much so, that a small storm, much smaller than the historically big storms, broke them.
And what of Florida? Who cares if the beach recedes by an increase in sea level in 100 years? The difference between high tide and low tide, is much greater than the difference between 2007 and 2107 in average sea level. Yet you don't hear the Left wax doom and gloom about high tide.
And what if, for argument's sake, in 100 years, the beach is pushed back enough in Florida to claim a beachside villa? Why should the Left, and the socialists care? They resent those who own those villas anyway, for their own political reasons. All an increase in high tide by 2 feet in 100 years would mean, is that the rich lose their beachside houses, and the poor people on the street behind them, get new beachfront property, thereby achieving the very transfer of wealth the socialists seek in the first place. lol.
Perhaps the fact that so many Hollywood lefties own those very beachfront houses, is the real reason they are in cohorts with Gore over rising sea levels?
In Marxist fashion, I say, "Power to global warming! Push the rich into the sea! Transfer prime beach real estate to the poor!"
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