20-Year Intense Downpours to Occur Every 6 Years

"My conclusions in 1988 were built on a wide range of inputs from basic physics, planetary studies, observations of on-going changes and climate models," Hansen told ABC News in an e-mail. "The evidence was strong enough that I could say it was time to 'stop waffling'. I was sure that time would bring the scientific community to a similar consensus, as it has."

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He stated, "The next President and Congress must define a course next year in which the United States exerts leadership commensurate with our responsibility for the present dangerous situation."