Is the climate warming?

Summary form only given. The balance of evidence suggests that the climate is not warming. A US National Research Council report has highlighted, but not explained, the disparity between different data sets: while a variety of surface thermometers report a substantial warming trend, microwave sensing units (MSU) on weather satellites, and also radiosondes carried in weather balloons, show little if any warming of the atmosphere in the last twenty years. As is well understood, however, climate models predict the opposite, namely a stronger warming trend for the atmosphere than for the surface. In further investigating this puzzling discrepancy involving different observing methods as well as theoretical models, the authors hypothesize that the recent surface trends may not be credible. They note that while there is general agreement that the global climate warmed before 1940, and then cooled slightly until about 1975, the well-controlled surface temperature data for the United States and Europe do not show any appreciable post-1940 warming, after correction for local urban warming ("heat islands"). This lack of warming throws doubt on the reported global surface trend. Further, proxy data from tree rings, ice cores, etc. show no post-1940 warming trends; many even show a cooling trend after 1940. The observations of Arctic sea-ice shrinking, deep-ocean warming, glacier-length changes and sea-level rise are explained as a delayed consequence of earlier climate warming; they are all in good accord with the hypothesis that the Earth\´s climate has not warmed appreciably in the past 60 years.