Friday, August 24, 2007
Climate change and tipping points
One of the fears of serious climate scientists and entirely unserious activists is that the impact of relatively small changes in the climate may be non-linear, because they might force a "tipping point." Famous examples include the melting of the Arctic permafrost (which could release a lot of methane, a far more powerful greenhouse gas than CO2), the melting of Greenland's ice sheet (which would raise sea levels dramatically and drive other changes), and the reorganization of the Atlantic "thermohaline circulation" (more popularly known as the "salt conveyor," which could stop the Gulf Stream and lower temperatures in Northern Europe to the point of destroying the productivity of its agriculture). With regard to this last, Jonah Goldberg links to news that suggests that Europeans do not yet have to stock up on snow shovels.
For much more on tipping points, both historical and potential, both natural and anthropogenic, I commend to you this recent article. It describes the history of sharp swings in the planet's climate and the prospects for any number of human-induced tipping points. Here is the conclusion, which is reassuring or disturbing, depending on how concerned you are already:
Our present warming commitment alone seems insufficient to tip any of the elements we have identified. However, it could get us close to the threshold for irreversible melt of the Greenland ice sheet. If that threshold is at the nearest end of its estimated error range (1 °C further global warming) then it will be nearly impossible to avoid by mitigation unless we are lucky and the climate sensitivity is at the bottom end of its uncertainty range (circa 1.6 °C warming for a doubling of pre-industrial CO2). If the threshold is further away (we estimate an upper limit of 2 °C global warming) then mitigation would still need to be extremely aggressive to avoid it. Given this, it seems prudent to design long-term adaptation strategies in anticipation of a progressive melt of the Greenland ice sheet. Critically there remains an argument for mitigation even when the threshold is passed because the rate of GIS melt and the corresponding contribution to sea level rise depends on how far the threshold is exceeded.
Do read the whole thing. Even if you are a proud "skeptic," it always pays to challenge your assumptions.
7 Comments:
By 
, at
Fri Aug 24, 09:13:00 AM:
I read an article in the last month or two on some recent research that bears on this: to wit, the Gulf Stream does NOT moderate Europe's climate. Rather, the warm air over Europe gets there as a result of the Rocky Mountains. Super short version: Air masses change shape crossing the Rockies, then as a result of the sherical rotatation of the globe and principal of conservation of angular momentum, that forces them to the southeastern US, then as they regain their old shape, they turn north again, and arrive warm and moist in Europe. By his study, the Gulf Stream accounts for about 1 degree of warmth, the Rocky Mountin effect for 15 or 20 (IIRC). If that's true, the potential disaster of losing the Gulf Stream would NOT be frozen Europe. Which does not mean it would not be a disaster at all, just maybe different. But the article I recall also indicated that no one paid much attention to this guy, even to challenge his study. I'd be curious to see more on it, if you know of anything.
By , at
Fri Aug 24, 09:37:00 AM:
I found the article. I think it relates to, but does not contradict, the "tipping point" idea.
http://www.americanscientist.org/template/AssetDetail/assetid/51963?fulltext=true&print=yes
By , at
Fri Aug 24, 09:47:00 AM:
> entirely unserious activists
What does this mean? Who are you referring to?
By 
SR, at
Fri Aug 24, 06:11:00 PM:
Most if not all the tipping points identified in the aritcle are local.
I doubt there is any computer model
(remember, that's all global warming scientists have) which can predict the tipping acurately enough to know what to do to prevent them. We wouldn't want to take ineffictive action, would we?
By , at
Fri Aug 24, 10:23:00 PM:
Well, the Sun could have a massive flare, which for sure would cause a tipping point.
But I think this sort of "tipping point" idea indicates a lack of a grasp on the nature of climate and understanding how much like a heat engine it behaves, and how various natural effects tend to "buffer" dramatic changes. There are boundary conditions to any heat engine, and you're asking if a small, incremental change can push the climate beyond boundary conditions.
This sort of thing tends to befuddle the educated layman, which is what one type of "global warming" enthusiast tends to promote. "The Environmental Apocalypse is coming to punish capitalism, and especially Americans and their big SUV's".
For every push there is a pull, a check and balance for many types of changes. That doesn't mean something catastropic COULDN'T happen, just somewhat unlikely.
Heat the oceans? Result:Increase in the cloud deck, and increase the amount of light (and heat) reflected back into space by a change in the Earth's albedo.
Melt more of the polar ice? Increase in the saline gradient (differential in salt water concentrations), causing a greater velocity of circulation of the oceans, to shed heat.
Equilibriums in climate change over the eons (the Sahara Desert was a lush tropical area 9,000 years ago), and we may be heading into a naturally warmer era, with anthropogenic inputs increasing the amplitude of weather changes in some areas of the Earth, or we're just in a cycle that may end soon.
Concerned? Yes, because enough fundamental science isn't being done to understand basic principles.
Alarmed? No, because this sort of "panic" about weather has been going on for some time.
"Everybody talks about the weather, but nobody does anything about it"- Mark Twain, sometime in the late 19th century.
-David
By , at
Sat Aug 25, 10:25:00 AM:
Some of these climate change alarmists claim that even A TEENIE WEENIE TEMPETURE CHANGE IS DISASTER AND SIGNS OF GLOBAL WARMING AND BLABBERING IDIOTS LIKE AL GORE CALLED CLOBAL WARMING THE NUMBER 1 THREAT TO LIFE ON EARTH WHAT A LOAD OF HORSE POO
By , at
Sun Aug 26, 12:32:00 AM:
And since 1970s the enviromentalist wackis have been saying WE HAVE ONLY TEN YEARS LEFT TO SAVE THE PLANET and now those wackos from GREENPEACE have said WE HAVE ONLY 5 YEARS LEFT and AL GORE gose on THE HISTORY CHANNEL and says that global warming is the number 1 threat to the planet THEIR ALL LIARS AND BLABBERING IDIOTS RRAAWWWKKK RRRAAAWWWKKK
