Global warming: what does the science tell us?

Computer models predict that clear signs of the greenhouse effect should have appeared as a consequence of increases in greenhouse gases, equivalent to a 50% increase in carbon dioxide in the last 100 years. The predictions are contradicted by the climate record in nearly every important respect. Contrary to the models: (1) the Northern Hemisphere has not warmed more than the Southern Hemisphere, (2) high latitudes have not warmed more than low latitudes, and (3) the U.S. has not shown the predicted warming trend, although this is the largest area in the world for which well-distributed, reliable records are available. Finally, all of the computations of the greenhouse effect show an accelerating increase in temperature in the 1980s, reflecting the rapid increase in greenhouse gases in recent years. However, measurements from orbiting satellites with a precision of 0.01.C show no trend to higher temperatures in the 1980s. (author)