Climate scientist James Hansen gave prominent U.S. Senate testimony on global warming on June 23, 1988. He testified before the Senate Committee on Energy and Natural Resources during a period of unusually high temperatures and drought in the United States.
Hansen, then director of NASA’s Goddard Institute for Space Studies, argued that the greenhouse effect had already begun altering Earth’s climate. He linked observed warming to the accumulation of human-produced greenhouse gases and presented climate-model projections under several emissions scenarios.
The hearing became a landmark in the public history of climate science because it brought anthropogenic global warming into a major national political discussion. Hansen’s appearance received substantial media attention and helped make climate change a prominent policy issue, although scientists had been studying the underlying physics and evidence for decades.
The testimony is sometimes confused with Hansen’s earlier Senate appearances in 1986 and 1987. Those hearings also concerned climate and atmospheric issues, but the especially prominent 1988 testimony is the event identified by this question.