THE OBSERVED GLOBAL WARMING RECORD - WHAT DOES IT TELL US

Global, neat-surface temperature data sets and their derivations are d iscussed, and differences between the Jones and Intergovernmental Pane l on Climate Change data sets are explained. Global-mean temperature c hanges are then interpreted in terms of anthropogenic forcing influenc es and natural variability: The inclusion of aerosol forcing improves tile fit between modeled and observed changes hot does not improve the agreement between the implied climate sensitivity value and the stand ard model-based range of 1.5-4.5 degrees C equilibrium warming for a C O2 doubling, The implied sensitivity goes from below the model-based r ange of estimates to substantially above this range, The addition of a solar forcing effect. further improves the fit and brings the best-fi t sensitivity into tile middle of the model-based range, Consistency i s further improved when internally generated changes are considered, T his consistency, however, hides manly uncertainties that surround obse rved data/model comparisons, These uncertainties make it impossible cu rrently to use observed global-scale temperature changes to narrow the uncertainty range in the climate sensitivity below that estimated dir ectly from climate models.