Comment on “Heat capacity, time constant, and sensitivity of Earth's climate system” by S. E. Schwartz

Abstract

[1] In a recent paper, Schwartz [2007] (hereinafter referred to as S07) estimated climate sensitivity using globally averaged observed time series. He estimated the planet’s effective heat capacity and ‘‘pertinent time constant’’ from ocean heat content and observed global temperature records, assuming that the latter can be modeled as a firstorder Markov (AR(1)) process after removing the trend due to climate forcing by subtracting a linear trend. [2] As S07 correctly states, the autocorrelation of an AR(1) process at lag Dt follows the simple relation