Chapter 12: A Climate of Healthy Skepticism Summary and Analysis

In 1988, NASA climatologist James Hansen testified before Congress that the chance for a natural increase in the global temperature of .4 degrees centigrade that had occurred from the 1950s was about one percent. He told the lawmen that the trend for that time period was evidence of real warming and that it was being caused by the greenhouse effect. Has Hansen's prediction proven to be accurate?

Noisy data can obfuscate the signal. Long before industrialization, there were cycles of warmer and cooler weather. However, there is evidence of the greenhouse effect. In 1990, the United Nations issued a report on climate change. The report was developed by a team of hundreds of scientists from around the world. Two major findings were cited. First, "there is a natural greenhouse effect that keeps the Earth...