Solution

 

Waiting for several suggestions.

 

 

 

clip8711

 

Real temperature goes from 1.1 C to 2 C when CO2 increases from 420 to 472 ppm

I is (2-1.1)/(472-420) = 0.0173 C/ppm

CO2 increase is 12.38 %  t increase 0.9 C  

sys := {1.443*x*ln(420/275) - 1.443*x*ln(400*1.1238/275) = 0.9};

evalf(solve(sys, {x}));   x= -9.182109498

 

 

 

 

 

The IPCC line based on cs=3  :    2C from 275 ppm to   450 ppm  

(2-0)/(450-275)  =   0.0114 C/ ppm

 

1.443*cs*ln(420/275)=1.1

1.443*cs*ln(474/275)=2