A 1988 Climate Warning Was Mostly Right

On a 98-degree June day in Washington in 1988, physicist James Hansen told a U.S. Senate committee that “global warming is now large enough that we can ascribe with a high degree of confidence a cause and effect relationship to the greenhouse effect.” Hansen, at the time director of the National Aeronautics and Space Administration’s Goddard Institute for Space Studies, elaborated that “with 99% confidence we can state that the warming during this time period is a real warming trend.”

Those assertions made headlines around the world, and can be said to have started the public and political discussion over global warming (the scientific discussion was already well under way) that continues to this day. They also caught Hansen some flak from fellow climate scientists who thought he had expressed himself with more certainty than warranted. Indeed, the scientific paper on which Hansen based his testimony, which he wrote with seven co-authors and was published that August in the Journal of Geophysical Research, cautioned that it was not yet certain that the warm temperatures of the 1980s were the product of the greenhouse effect.