Re: [asa] Climate Progress

From: David Campbell <>
Date: Tue Dec 15 2009 - 12:58:57 EST

Although it is a useful starting point, there actually is a lot of
ambiguity and difficulty in this list.

> Specifically, we challenge supporters of the hypothesis of dangerous human-caused climate change to demonstrate that:<

"Demonstrate"-to whose satisfaction? To a reasonable impartial
observer (which is almost always defined as "someone who agrees with
me", on whatever side of whatever issue)? To someone who is already
committed to disregarding the evidence? To someone who has no clue
about the detailed considerations involved?

>        1. Variations in global climate in the last hundred years are significantly outside the natural range experienced in previous centuries;

The key problem is the rate of change (extremely rapid), rather than
absolute temperature and correlates such as sea level (which have
certainly been higher before about 2.5 million years ago, very likely
(temperature) or certainly (sea level) was higher about 100,000 years
ago, and at least locally has been comparable or slightly higher on
occasion in the past 10,000 years).

>        2. Humanity’s emissions of carbon dioxide and other ‘greenhouse gases’ (GHG) are having a dangerous impact on global climate;

"Dangerous"-has exterminated a few species that we know of,
contributed to the deaths of many people, ongoing response to current
conditions (even with no more CO2) will cause sizeable disruptions in
current agriculture, low-lying areas, etc. But not as dangerous as a
large asteroid about to collide with earth, or all-out nuclear
warfare, or some other conceivable scenarios.

>        3. Computer-based models can meaningfully replicate the impact of all of the natural factors that may significantly influence climate;

"All" of the factors that "may" is not reasonable. E.g., some nearby
star could explode and impact the climate. Rather, a reasonable
standard is whether the models accurately incorporate all the known
factors and produce results in keeping with the available empirical

>        4. Sea levels are rising dangerously at a rate that has accelerated with increasing human GHG emissions, thereby threatening small islands and coastal communities;<

Same sort of problem with "dangerous." Is the sea level going to jump
six feet and wash Miami out to sea? No. There's no need to run to
escape. But it is time to start packing and finding a new place at
higher elevation, not just for people with a beach house but also for
most of Bangladesh and many other poor regions of the world.

>        5. The incidence of malaria is increasing due to recent climate changes;

The precise question is whether malaria and other
temperature-sensitive diseases are spreading into areas where they did
not previously occur due to climate change. The answer is yes-malaria
is occurring at higher altitudes in Africa which had been free of
malaria. (Schistosomiasis-host snails are now found as far north as
Charleston, SC.)

>        6. Human society and natural ecosystems cannot adapt to foreseeable climate change as they have done in the past;<

On what time frame? It takes on the order of a few million years for
faunas to recover in the fossil record after a significant climate
shift, and that's assuming that climate stabilizes after the shift and
no other significant disruptions are involved. Human society _can_
respond more quickly, but not if it postpones action while denying
that it is needed or while claiming it costs too much.

>        7. Worldwide glacier retreat, and sea ice melting in Polar Regions , is unusual and related to increases in human GHG emissions;

Such retreat has happened in the geologic past; the issue is whether
the current retreat is human-caused and whether it differes in speed
or other characters from past events.

>        8. Polar bears and other Arctic and Antarctic wildlife are unable to adapt to anticipated local climate change effects, independent of the causes of those changes;<

Although polar bears primarily feed by catching seals at their air
holes in ice, a lifestyle hard to maintain without ice, they are able
to scrounge dumps and may have the flexibility to survive, albeit
under very altered conditions. But most of the species most affected
have much poorer PR. Mountaintop animals are also at high risk, as
are those on islands or otherwise constrained in their ability to

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 Tue Dec 15 12:59:21 2009

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