In a new article just published in the Journal of Geophysical Research-Atmospheres, Pat Michaels and I have concluded that the manipulations for the steep post-1980 period are inadequate, and the global temperature graph showing warming is an exaggeration, at least in the past few decades. Along the way I have also found that the UN agency promoting the global temperature graph has made false claims about the quality of their data. The graph comes from data collected in weather stations around the world. Other graphs come from weather satellites and from networks of weather balloons that monitor layers of the atmosphere. These other graphs didn’t show as much warming as the weather station data, even though they measure at heights where there is supposed to be even more greenhouse gas-induced warming than at the surface. The discrepancy is especially clear in the tropics.

The surface-measured data has many well-known problems. Over the post-war era, equipment has changed, station sites have been moved, and the time of day at which the data are collected has changed. Many long-term weather records come from in or near cities, which have gotten warmer as they grow. Many poor countries have sparse weather station records, and few resources to ensure data quality. Fewer than one-third of the weather stations operating in the 1970s remain in operation. When the Soviet Union collapsed in the early 1990s, more than half the world’s weather stations were closed in a four year span, which means that we can’t really compare today’s average to that from the 1980s.  Read a background summary here and a technical paper published in the JGR December 2007 here.

McKitrick is an Associate Professor at the University of Guelph. Michaels contributed to this research while a member of the Department of Environmental Sciences at the University of Virginia, and while a visiting lecturer at Virginia Tech. He is now with the Cato Institute