Climate Sensitivity

IPCC AR4 Working Group 1 Summary for Policymakers, page 12

"The equilibrium climate sensitivity is a measure of the climate system response to sustained radiative forcing. It is not a projection but is defined as the global average surface warming following a doubling of carbon dioxide concentrations. It is likely to be in the range 2°C to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values."

Alternative estimate for climate sensitivity

In his paper "Where should humanity aim?" James Hansen and co-authors have estimated that equilibrium climate sensitivity is 6°C, double the IPCC estimate.

The following papers are relevant to the question of what is the appropriate value for the Earth's climate sensitivity: 

1. Uncertainty in predictions of the climate response - Stainforth et al - Nature Jan 2005.pdf

2. Missing feedbacks and underestimation of future warming Torn Harte 2006.pdf

3. Positive feedback between global warming and CO2 - Scheffer Cox 2005.pdf

4. Why is climate sensitivity so unpredictable G.H.Roe et al Science 2007.H.Roe et al Science 2007.pdf

5. Atmosphere Call Off the Quest - Allen and Frame Science Oct 2007.pdf

6. The millenial atmospheric lifetime of anthropogenic CO2 - Archer & Brovkin 2008.pdf

7. Target Atmospheric CO2 - Where should humanity aim - Hansen et al 2008.pdf

8. The equilibrium sensitivity of the Earth's temperature, 2008.pdf

9. Irreversible climate change due to carbon dioxide emissions Feb 2009.pdf

10. Greenhouse-gas emission targets for limiting global warming to 2C - Meinshausen et al 2009.pdf

11. Warming caused by cumulative carbon emissions towards the trillionth tonne - Nature April 2009.pdf

12. Too much of a bad thing - Nature April 2009 Schmidt and Archer.pdf