Re: [asa] Re: Glenn's blog post

From: David Campbell <pleuronaia@gmail.com>
Date: Mon Mar 30 2009 - 16:08:48 EDT

> "The problem of present-day global warming is not the absolute
> temperature but rather the rate of change.  It doesn't matter whether
> it was somewhat warmer in the early Holocene; what does matter is that
> climate, ocean acidity, etc. are changing faster than many organisms
> (including many humans) can easily adjust."<<<

> I hear this rate of change argument all the time. Once again, geology shows
> it to be utterly false, like everything else in climate change, the recent
> past has endured the same conditions and rates (or worse conditions and
> higher rates of change.

> The Younger Dryas period saw a change in temperature of 5 deg C in about 30
> years! see  Figure 3 of Alexi M. Grachev and Jeffrey P. Severinghaus "A
> revised +10+ or -4 degrees C magnitude of the abrupt change in Greenland
> temperature at the Younger Dryas termination using published GISP2 gas
> isotope data and air thermal diffusion constants"Quaternary Science Reviews
> (March 2005), 24(5-6):513-519
>
> I have no doubt that no one will go look at that picture. It is easier to
> continue to believe rather than go look up that article. But that rate of
> change is about 5/3= 1.66 deg C per decade, more than 10 times what the IPCC
> says is awful.

Actually, they estimate that there was a change of about 10 degrees in
probably no more than 50 years, a 2 degree per decade or more change.
However, that's the change at a particular site in Greenland, not a
global average temperature change.

Human activity has changed the situation a good deal since the Younger
Dryas, however. Present-day humans are much less likely than those
10,000 years ago to be wandering hunter-gatherers who will simply move
their camp if the ocean or glacier or whatever gets too close. Only a
slight increase in sea level displaces millions of people in
Bangladesh, for example. A slightly drier or wetter year than usual
in some region of the U.S. has people calling for disaster relief
because the crops don't grow so well or because homes built on flood
plains flood or because water supplies go low when there's no effort
to conserve it. People do not adjust well to change on a time scale
that's long enough to not be immediately obvious but short enough to
require response.

Additionally, human modification of the landscape means that most
habitats are significantly fragmented. Species confined to a
particular patch of habitat are much less likely to have suitable
connecting habitats today than they did centuries ago. Pollution and
other human pressures may also make it hard for an already stressed
population to make one more adjustment. Larger populations are more
likely to have adequate genetic variations to allow for some
adjustment.

Some time ago, I heard a talk that claimed that only one Pleistocene
species of insect was known to have become extinct before modern
times, and that was a fly that parasitized mammoths. Apparently the
insects were able to move around or otherwise find ways to survive,
even apparently poor movers like flightless beetles. Yet we see a
number of species today that seem to be having difficulties in keeping
up with the changes. Were there similar problems back in the Younger
Dryas and things have adjusted by now, only to need a bit of
adjustment that will come quickly, or will there be serious problems
in the meantime?

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Mon Mar 30 16:09:35 2009

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