Impact of dataset choice on calculations of the short-term cloud feedback
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Dessler [2010, hereafter D10] estimated the magnitude of the cloud feedback in response to short-term climate variations and concluded that it was likely positive, with an average magnitude of +0.500.75 W/m2/K. This paper investigates the sensitivity of D10's results to the choice of clear-sky top-of-atmosphere flux (Rclear-sky), surface temperature (Ts), and reanalysis data sets. Most of the alternative Rclear-sky data sets produce cloud feedbacks that are close to D10, differing by 0.2-0.3 W/m2/K. An exception is the Terra SSF1deg Rclear-sky product, which produces an overall negative cloud feedback. However, a critical examination of those data leads us to conclude that that result is due to problems in the Terra Rclear-sky arising from issues with cloud clearing prior to July 2001. Eliminating the problematic early portion yields a cloud feedback in good agreement with D10. We also present an alternative calculation of the cloud feedback that does not require an estimate of Rclear-sky, and this calculation also produces a positive cloud feedback in agreement with D10. The various Ts data sets produce cloud feedbacks that differ by as much as 0.8 W/m2/K. The choice of reanalysis, used as a source of Rclear-sky or as adjustments for the cloud radiative forcing, has a small impact on the inferred cloud feedback. Overall, these results confirm the robustness of D10's estimate of a likely positive feedback. 2013. American Geophysical Union. All Rights Reserved.
