The climate sensitivity and its components diagnosed from Earth radiation budget data

One of the major uncertainties in our ability to predict future climate change, and hence its impacts, is our lack of knowledge of the Earth's climate sensitivity. Here, we combine data from the 1985-1996 Earth Radiation Budget Experiment (ERBE) with surface temperature change information and estimates of radiative forcing to diagnose the climate sensitivity. Importantly our estimate is completely independent of climate model results. We find a climate feedback parameter of 2.3±1.3Wm-2K-1, which corresponds to a 1.0-3.6 K range for the equilibrium warming due to a doubling of carbon dioxide (assuming Gaussian errors in observable parameters, which is approximately equivalent to a uniform prior in feedback parameter). We present an argument that this value is likely to be representative of longer-term climate change. Further, we are able to use our methodology to: 1) retrieve shortwave and longwave components of climate feedback; and 2) suggest clear-sky and cloud feedback terms. Comparing climate models to these results will provide an important test of their feedback mechanisms.