>> << Steve writes:
>Uhhm, you need to re-read what I wrote. I did not write that the increase
>was only 2%, but that man's contribution to atmospheric CO2 was something
>around 2-3%, IIRC.
>
Here's an analogy: A bath is being filled at the rate of 100 litres per
minute, and draining at the same rate. The water level stays constant. Now
increase the filling rate to 102 litres per minute without altering the
rate of drainage and pretty soon the bath overflows, causing who knows what
damage to the floor below.
To a first approximation that seems to be the situation with global
warming, where our small anthropogenic inputs of CO2 have now caused CO2
levels in the atmosphere to rise by about 30% over the last century or so.
>Well actually the most common and serious GHG is water vapor. IIRC, water
>vapor is the GHG that will be the main driver. That is the warming
>induced by CO2 will lead to greater water evarporation, which means more
>warming, which means more evaporation, more warming, ad infinitum.
>
So shouldn't you be rather worried about this?
>And yes, CO2 is actually not that big a deal compared to say methane.
>
CO2 is responsible for well over 50% of the global warming. Most of the CO2
also stays in the atmosphere for a century or so, while methane disappears
after only about a decade.
>Eeee, climate models. I have seen some of the output from these models
>and it ain't that pretty. They do okay sometimes, and poorly others.
>Remember these are very simplistic computer simulations and as far as
>predicting temps, their track record to date is pretty poor.
>
The most recent models that include sulphates do a passable job of
predicting average temperature change (certainly better than earlier models
which neglected them).
So my take on all this is pretty similar to Michael's (except that I
probably wouldn't put my subjective probability quite as high as 0.99, as I
know the literature about overconfidence of subjective estimates).
For what it's worth, I make my living trying to calculate the probabilities
and the 'stakes' on both sides (impacts and costs of taking action). And
it's not absolutely clear from the calculations whether taking action to
cut our emissions is a good bet or not. The calculations are just very hard
to do.
Chris
Chris Hope, Judge Institute of Management Studies,
University of Cambridge, Cambridge CB2 1AG, UK.
Voice: +44 1223 338194. Fax: +44 1223 339701
e-mail: [log in to unmask]
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