1.1. Synopsis
[1] Reanalysis of the autocorrelation of global mean
surface temperature prompted by the several comments,
taking into account a subannual autocorrelation of about
0.4 year and bias in the autocorrelation resulting from the
short duration of the time series has resulted in an upward
revision of the climate system time constant determined by
Schwartz [2007] by roughly 70%, to 8.5 ± 2.5 years (all
uncertainties are 1-sigma estimates). This results in a like
upward revision of the climate sensitivity determined in that
paper, to 0.51 ± 0.26 K/(W m2), corresponding to an
equilibrium temperature increase for doubled CO2 of 1.9 ±
1.0 K, somewhat lower than the central estimate of the
sensitivity given in the 2007 assessment report of the
Intergovernmental Panel on Climate Change, but consistent
within the uncertainties of both estimates. The conclusion
that global mean surface temperature is in near equilibrium
with the applied forcing continues to hold. Forcing over the
twentieth century other than that due to greenhouse gases,
ascribed mainly to tropospheric aerosols, is estimated as
1.1 ± 0.7 W m2.