An enthusiastic crowd welcomed former President Bill Clinton to Benaroya Hall in Seattle this afternoon. He was here to address the U.S. Conference of Mayors. And he had them at hello. Acknowledging his introduction by Mayor Doug Palmer of Trenton, N.J., who is the president of the U.S. Conference of Mayors, Clinton said: "Thank you for your friendship to me and my candidate!" The crowd loved it. Clinton used his remarks to offer his congrats to the mayors for their leadership on climate change. But he also took the occasion to offer a dissertation-like speech about the problems affecting the world. How could he resist a captive audience? The three most severe challenges he cited are: economic inequality; identity conflicts (racial, ethnic, religious); and, yes, environmental un-sustainability. Of course, it was the third problem that he elaborated on most, given the climate-change theme of the conference. "I think it's wonderful that Al Gore got the Nobel Prize for what he's been saying for 20 years," Clinton said to wide applause. Interestingly, he said that the climate problem is even worse than what is depicted in An Inconvenient Truth, Gore's Academy Award-winning documentary on the topic. Gore addressed the mayors earlier in the afternoon via satellite. And yet, Clinton's tone was mostly optimistic. "It is the greatest economic opportunity we've had since we mobilized for World War II," he said. He believes new and expanded businesses will open up if we change our ways. Clinton, whose own foundation has become increasingly involved in combating climate change, was proud to announce a new partnership with the mayors conference. He will include all the conference's cities in a buying consortium that his Foundation is already sponsoring on a smaller scale. The goal is to expand the buying power of green products and thereby lower the costs for everyone. "If we organize the market for green products, we can drive down prices and help the climate," he said. "The potential is almost too great to contemplate." Aside from his reference to Hillary, the biggest laugh seemed to come when he talked about retrofitting his own house in New York to be more energy efficient. He noted that he had "plenty of money" and "lots of contacts" and yet it was still hard for him to get the job done. It needs to be easier, he argued, or else it's never going to be done on a large scale in homes across America. He ended with how important it is for the U.S. to send a signal. "We will not get a global agreement on climate change unless people like you prove that it's not a burden."