NASA Twenty-nine years ago, James Hansen, the director of NASA's Institute for Space Studies, told the US Senate that the question of the day — whether climate change was happening — was no longer in doubt. "It is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here," Hansen told reporters at the time. Hansen's testimony before the Senate Committee on Energy and Natural Resources on June 23, 1988 — coincidentally the hottest June 23 in the District of Columbia's recorded history — is frequently considered the most important climate change hearing in history. The greenhouse effect that Hansen described — in which the widespread combustion of fossil fuels causes a heat-trapping buildup of gases like carbon dioxide in the Earth's atmosphere — has since become almost common knowledge.