AJH wrote:
On Thu, 18 Sep 2008 22:30:03 +0100, The Natural Philosopher
wrote:

Things like pollution, water vapour and certain other chemicals that are
greenhouse contributors wash out of the air pretty quickly: Co2 does not.

For the purposes of its effect on trapping re radiation I think water
vapour can be considered a permanent effect but I'm open to arguments
on this. As far as I understand it, with a clear sky, the amount of
water molecules depends on the relative humidity, which will always be
less than 100% but what will the minimum be? The conjecture is that
there will always be sufficient water molecules to trap those
wavelengths that it can absorb whereas this is not true of CO2. What
puzzles me is that the CO2 will be fairly equally distributed through
the whole depth of the atmosphere, because of the gas laws and to do
with partial pressures, whereas, given the clear sky, the water
molecules will be concentrated in the warmer layers next to the earth
because otherwise their dew point would have been reached.

The big pollutant, from poor secondary combustion, that has a short
life in the atmosphere is soot or particulates. These seem to have an
effect of blocking incoming solar energy when in the air and absorbing
it, reducing albedo, once they settle or are washed out.
Ultimately we (in te west anyway) can create live and grow food in
artificial ecospheres if we have to, but boy we will need a lot of
energy to build and run them.

Not to mention exploiting finite resources, most renewable energy
deployment requires more concrete, steel and other "stuff" than our
current generation capacity per installed kW.


Yes. Its like 'organic' vegetables, worthy, but usually disease ridden,
small and not very nice to eat.