Climate sensitivity Question

[duwayne]

I meant to post this in the Global Warming section so I've reposted it there.

For those of you with some math expertise.... I'd like some help.

Givens for the purpose of this calculation:

1. Atmospheric CO2 concentration in 1850 was 270 ppm

2. Current CO2 concentration is 400 ppm

3. The global temperature increase from 1850 to current was 0.80C

4. All of the temperature increase was and will be due to CO2

5. The global temperature increase is proportional to the logarithm of the increase in CO2

Question: What will the global temperature be versus 1850 when the atmospheric CO2 concentration reaches 520 ppm?

My calculation is a warming of 1.41C. Is that correct?

[sigurdur]

Yes.

[douglavers]

I better repeat my post elsewhere, as incomprehension rules OK.

There is a terrible thing called saturation, probably only understood by spectroscopists.

CO2 only absorbs in two radiation bands, from memory one of which overlaps with H2O [ that funny stuff that fish swim in].

Unfortunately, the first 20 ppm absorbs about half the radiation that CO2 is capable of absorbing. The next 20 ppm absorbs another half, and so on.

By the time one reaches 400 ppm, that means that about 99.999% of the radiation that carbon dioxide can ever absorb has already happened. [(1-0.5^20 as %]

In a nutshell, that is why all this alarmism over increases in CO2 is absurd. Otherwise the planet would have gone into heat death when the concentration was 4000 ppm.

But don't expect journalists or the green movement to understand it.

It is also why duwayne's calculation is wrong.