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A few notes on climate sensitivity
Sensitivity means how much warming we can expect from one extra watt of surface radiation.
This is expressed as °C/(W/m2)
Several methods have been used to arrive at an answer
the two I like are:-
1 The temperature during the last ice age was 5.5 Deg c cooler than today and the difference in surface radiation is estimated to be 7.3W/m2 giving a figure of 0.75°C/(W/m2)
2 The difference between solar maximum and solar minimum is 1.3 W/m2 but this is the amount of power arriving at the earth's plane this has to be reduced by 30% to account for albedo and by a factor of 4 because the earth is sphere and not flat. The temperature difference from peak to trough is estimated to be about 0.18 °C. This translates to 0.2275 W/m2 against 0.18°C or 0.79 °C/(W/m2) but it is probably an underestimate due to lag effects.
There is no dispute that a doubling of CO2 in the atmosphere will increase surface surface radiation by 3.7 W/m2. There is a high level of confidence in this figure. It is often expressed in the form that a doubling of CO2 would directly increase temperature by 1 °C provided no other factors are involved but they are so we get:-
3.7 W/m2 for CO2
and 0.77°C/(W/m2)
Therefore we can expect the temperature to rise by at least 2.85°C for a doubling of CO2.
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Pollution is not the solution
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