Former Sen. Timothy Wirth, D-CO, president of the U.N. Foundation, speaks at National Press Club to mark the 20th anniversary of the "Hansen Hearing," the Senate Energy Committee's 1988 hearing on climate change, which marked the first time a top climate scientist declared that global temperatures had risen beyond the range of natural variability in Washington on June 23, 2008. (UPI Photo/Patrick D. McDermott)