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47 comments on HOT Hot hot
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47 comments on HOT Hot hot
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The change of 1 C from medieval warm period to the little ice age is interesting to compare to the changes expected this century.
1 C change took about 600 years.
Earth has already warmed about 0.6 C in the past 30 years, perhaps the next 0.4 C will happen in the next couple of decades?
That's 1 C in less than 60 years, or about 10 times the previous rate. If the same math is done for the global ice age to the start of the warm present the rate difference is about 100 times faster now.
Now how to place the importance of this rate into a context folks in the 21st century can understand....Okay, here it goes:
If you are driving a car at 60 miles per hour (ca. 100 km/hr) and decelerate to 0 mph in 10 seconds that is no problem.
But if you make the same change in 1 second you are probably dead or seriously impaired.
This is why all the talk about "the Earth has dealt with climate change before...." are so ridiculous. Sure it has, but not at this rate except during previous mass extinction events. It's like telling someone, don't worry, you have gone from 60 to 0 many times before!
If this was intended as a causal chain I think a more appropriate construction would be: 1) seriously impaired; 2) abrupt deceleration; 3) death.
Looking forward to the next post Euan. Cheers!
Jason, abrubt climate change is not new. The last six ice ages (in the last million years) all ended by methane bombs. Abrubt climate change in those periods is said to have happened in as little as 12 to 20 years with temp changes of 5C. It causes sea levels to rise in those surges at rates of 70cm/yr (3"/yr). In some deglaciations, the temp change was 11C overall.
The last time it happened, about 10k yrs ago, we lost the sabre tooth tiger and mammoths etc and the ecology of Earth has some changes but it was hardly catastrophic. Some folks resist change. But it is part of the natural process. Homo sapiens have been roaming for 60k yrs. They have gone thru this before. The pop'n likely dropped from 100k to 10k ... but Darwin (and MS) would probably say that was a good thing (from a genetics point of view) and helped clear out the neanderthals (tho i wonder sometimes).
Upon rereading your post, i notice that u acknowledge that this has happened before ... but mass extinctions came with it. That was because the inhabitants of the time were basically agrarian and stubborn. Oooops. That does not bode well for Heinberg's kool-aid drinkers, eh?!!
This isn't very accurate. Agriculture was not invented (as far as we know) before the start of the Holocene (around 10k years ago) (and modulo some South East Asian horticulturists). Since modern humans have been around for ~150k-~200k years, and in Eurasia for around ~50k years, the leading explanation for why we didn't invent agriculture/civilization till the Holocene - when we invented it numerous times independently - is that the climate was too unstable for us to stay in one place long enough until then. I don't know that this can be considered proven beyond a reasonable doubt (given that some of the possible evidence is under water and lots of mud). But still, given that no agricultural civilization has ever survived anything of the magnitude of a glacial-interglacial transition, the thought of abrupt climate changes should probably inspire some fear - though it's essentially impossible to quantify the likelihood of one in the 21st century.
Also, the methane forcing in Pleistocene deglaciations was less important than the CO2 forcings - "methane bomb" is rather misleading. And since there doesn't seem much reason to suppose the last deglaciation was any worse than previous ones, I'm inclined to accept the theory that early human hunters were the main factor in the mass mammal extinctions.
Certainly the Clovis people in North America lived for only a very short time (about 1000 years I think) before becoming something else-- 13000 years ago.
There distinctive trademark was the large bladed stone spearhead.
It appears that at the same time a number of the North American super-mammals were extincted.
This would be consistent with the impact of the Polynesians on New Zealand-- again a wave of extinctions, including the Dodo Bird.
I believe Diamond raises this point in Guns, Germs, and Steel. Clovis culture appears to be associated with the loss of North American mega fauna. The same loss of mega fauna is also found with hominid entry to the Australian continent.
Another interesting text is Sea of Slaughter by Farley Mowat. He documents the decline of all species in the Gulf of St Lawrence area with the arrival of European settlers.
Current research is discounting hunting for these extinctions. Not enuf bone damage on found carcasses. It is likely that the food chain was disrupted by the turning of the mass grasslands North of 60 to tundra. Large parts of yukon and alaska known as Beringia were ice free for much of last ice age. Mammoths starved. Saber tooth had no prey. etc etc.
References?
http://www.beringia.com/02/02mainb.html
Stuart et al, click on the "research notes" with each link. Unfortunately most of these were written in 95/96 and have not been updated with current research being shared at local seminars and lectures ... mostly by univ of alaska & univ of calgary paleantologists.
Of all the beringia fauna, wolf has adapted best over time. Much larger now due to absence of predators and new status of near top of the food chain.
With GW, deer are penetrating our are deeper. And that is bringing larger numbers of cougars.
Interesting research presently is why do sabre tooth cats have sabre. Mammoths don't have pierced neck bones. Slashing abdomen?
DNA et al testing allows new diet info by analysis of compounds in ancient teeth.
If i can get a Powerpoint from lecturers, i'll post it another time.
I believe there's still a very active debate on this subject with neither side having convinced the other. The Wikipedia has a fair summary. I expect there's some of both going on, but I find the idea that the extra ecological stress of humans was the main cause of so many extinctions in such a short time fairly persuasive.
You are getting into areas of my professional expertise. What has happened historically is probably not analogous to current changes due to rate differences.
See something some friends of mine wrote:
http://www.wfu.edu/~silmanmr/labpage/publications/consuelo.science.2004.pdf
I have also been part of modeling studies on the ecosystem impacts of such rapid change:
http://www.sciencemag.org/cgi/content/abstract/310/5750/1029?ijkey=rSvd9...
Jason: Your article is behind a paywall. Reading from the abstract, is it correct that the change in species composition lowers the above ground carbon sink?
Yes. This was the aspect of ecosystem function modeled and that was the general conclusion.
More specifically, a decline in species diversity that corresponds to a loss of functional diversity would tend to reduce carbon storage as a functional attribute of an ecosystem, especially an ecosystem being stressed.
Thanks for the response.
And that finding would apply to other forest types beyond the montane forest under study?
I recognize that question may be pushing beyond the findings of the research study but does the above appear to be likely?