Climate Sensitivity and the Response of Temperature to CO$_2$
  A review of some of the evidence for the IPCC's conclusion that doubling CO$_2$ levels will warm Earth significantly, in contrast to the claims of a recent article$^1$. Simply looking at raw temperature and CO$_2$ data over the past 150 years gives a transient response of roughly 2 K per doubling, in good agreement with IPCC conclusions based on far more extensive analysis. The 0.58 K of Ref. 1 is very unlikely. 
Arthur P. Smith