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: Hansen testified that Global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and observed warming...It is already happening now and The greenhouse effect has been detected and it is changing our climate now...We already reached the point where the greenhouse effect is important.