Via Anthony Watts, a new study from Georgia Tech has some interesting findings:
“Across the U.S. as a whole, approximately 50 percent of the warming that has occurred since 1950 is due to land use changes (usually in the form of clearing forest for crops or cities) rather than to the emission of greenhouse gases,” said Stone. “Most large U.S. cities, including Atlanta, are warming at more than twice the rate of the planet as a whole — a rate that is mostly attributable to land use change. As a result, emissions reduction programs — like the cap and trade program under consideration by the U.S. Congress — may not sufficiently slow climate change in large cities where most people live and where land use change is the dominant driver of warming.”
County-level land-use changes from 1950 to 2000, based on censuses of population, housing, and agriculture. A) change in population density; B) change in land area settled at “exurban densities” (i.e., 1 house per 1 to 40 acres); C) change in percent cropland (Brown et al. 2005).
This is similar to what we found around the world’s populated land areas in 2007 (McKitrick and Michaels, Journal of Geophysical Research): ” . . . extraneous, nonclimatic effects reduces the estimated 1980-2000 global average temperature trend over land by about half.”