Trying again:

Link if the picture does not appear

Here is a link to a physicist that discusses the relationship between CO2 and temperature as logathrimic.

Using his Temperature = Temperature0 + ln(1 + 1.2 x + 0.005 x2 + 0.0000014 x3) formula, I made the following spreadsheet:

Where CO2 is the PPM concentration (column V), Temp is in Celcius, and Chg is the temp less the previous temp. Plotting CO2 against Chg, the looks similar to that of the yellow 'extinction' graph. Of course, that is because Ln is in the formula. My version of the formula in open office calc is:

=$W$20+LN(1+1.2*V41+0.005*V41*V41+0.0000014*V41*V41*V41)