Lean, J.L. and Rind, D.H, 2008. How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006. Geophysical Research Letters 35: 10.1029/2008GL034864.
What was done
"To distinguish between simultaneous natural and anthropogenic impacts on surface temperature, regionally as well as globally," to quote the authors, "we perform a robust multivariate analysis using the best available estimates of each together with the observed surface temperature record from 1889 to 2006."
What was learned
Lean and Rind report that "contrary to recent assessments based on theoretical models (IPCC, 2007) the anthropogenic warming estimated directly from the historical observations is more pronounced between 45°S and 50°N than at higher latitudes," which finding, in their words, "is the approximate inverse of the model-simulated anthropogenic plus natural temperature trends ... which have minimum values in the tropics and increase steadily from 30 to 70°N." Furthermore, as they continue, "the empirically-derived zonal mean anthropogenic changes have approximate hemispheric symmetry whereas the mid-to-high latitude modeled changes are larger in the Northern hemisphere."
What it means
Because of what their analysis revealed, the two researchers concluded that "climate models may therefore lack -- or incorrectly parameterize -- fundamental processes by which surface temperatures respond to radiative forcings," which is a conclusion with which all of the world's "climate skeptics" would probably agree, and which should give all of the world's "climate alarmists" pause to consider the rationality of their calls for dramatic worldwide curtailment of anthropogenic CO2 emissions. To promote such unprecedented and coercive measures on the basis of model scenarios that "lack -- or incorrectly parameterize -- fundamental processes by which surface temperatures respond to radiative forcings" would appear to us to be the height of folly.
Intergovernmental Panel on Climate Change. 2007. Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Solomon, S. et al. (Eds.) Cambridge University Press, Cambridge, UK.