claim: 'On June 23, 1988, NASA scientist James Hansen testified before the House of Representatives that there was a strong cause and effect relationship between observed temperatures and human emissions into the atmosphere.
evidence: ...Dr. James E. Hansen of the National Aeronautics and Space Administration told a Congressional committee that it was 99 percent certain that the warming trend was not a natural variation but was caused by a buildup of carbon dioxide and other artificial gases in the atmosphere.