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Re: Human vs. natural influences on the environment




It's a matter of fundamental physics that changing the composition
of greenhouse gases changes the radiative balance of the earth, and
this can be made quantitative - it's between 4 and 5 watts per
square meter imbalance at the top of the troposphere per doubling
of CO2, for instance. I know of no serious workers in the field
who question this. The issue is what that means for us at the
surface.

Secondly, I'd point out that the change in the global mean
temperature should be considered as an indicator of climate change,
not a description of it. The error becomes obvious when compared
with a statement the likes of "I don't care if my body temperature
goes up a couple of degrees C - in absolute terms that's less than
a per cent". Ah, yes, but in terms of the changes in your metabolism,
it's huge. What we should be concerned about isn't how much the
temperature increases (we're pretty confident at this point that
it's nonzero and positive) but what that means to the general circulation.

It is this latter issue to which the infamous computer models are
applied. Getting the rough order of magnitude of the global mean 
increase is within the capability of calculations unaided by technology,
and is robust at least insofar as the error terms are clearly identified.

Where we're playing dice is how much that will cost us. This should
be treated as a risk/benefit scenario, not as a yes/no question, and
I find arguments as to whether the science is "good" or "bad" completely
worthless on both sides. The science is as good as it is, and that's the
information we have to make decisions, including decisions as to how
much to spend on the science. For what it's worth, the climate
science is a lot more solid than the economics, as far as I can tell.

As far as the human response to climate change goes, it seems to me
that the best information we have is historical and anthropological.
I am unconvinced that macroeconomics has much to say on time scales longer
than a decade, given its inherently crude metrics and its roughly 
half-year time constants. The historical and anthropological evidence 
shows considerable sensitivity of civilizations to climate shifts.
Technology probably reduces this. It's part of the risk/benefit problem
to estimate by how much.

As for species conservation, climate change looks likely to be an
enormous hit on an already serious situation. Another part of the big
picture is deciding how much we care about that. Even this is commonly
treated as a yes/no question. I wonder if democratic civilization will
ever act as a whole in a manner that is as grown up as even a marginally
competent free adult. 

I suppose they are libertarian types out there reading this who are
thinking "no, and so it shouldn't bother trying". Unfortunately, that's
betting on a lot of large scale problems breaking favorably. The radiative
physics of the atmosphere is not decided by the moral superiority or
inferiority of objectivism. It's decided by processes that were not made
by the hand of man.     

mt




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