In 1988, Dr James E. Hansen testified to a Congressional committee about the previously noted global warming trend. The cause, he said, was known with 99% certainty, to be the buildup of carbon dioxide and other artificial gases in the atmosphere trapping solar radiation. He identified the burning of fossil fuels as a major source of the problem. The impact was not a natural variation, but a long term effect that could last for centuries. “It is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here.” Hansen spoke to the Senate Energy and Natural Resources Committee as director of NASA's Institute for Space Studies in Manhattan. Other scientists also testified remedies were needed immediately.«