But all of them heard Monday about the critical role they have begun to play in addressing the global problem.

"You here are closest to the people," Robert Redford told the 45 leaders assembled at the Sundance Summit: A Mayor's Gathering on Climate Protection.

"This [conference] is really about tangible steps that can be taken and are being taken already" by local leaders.

A longtime activist and actor and the founder of Sundance, Redford is co-hosting the three-day meeting with Salt Lake City Mayor Rocky Anderson and the International Council on Local Environmental Initiatives. The meeting ends today with several how-to sessions on reducing combustion emissions that have been speeding up global warming in the past 150 years.

On Monday, New Mexico Gov. Bill Richardson told the local leaders they have "a tremendous impact on people's lives." A former U.S. energy secretary, he praised the mayors' initiatives promoting energy-efficiency, alternative energy and other programs that reduce the output of greenhouse gasses.

Former Vice President Al Gore spoke to the mayors at an invitation-only dinner. His topic? "Global Warming - Planetary Emergency." He has been on the road in recent months urging an aggressive response to climate change and touting the economic benefits of cutting planet-warming emissions now.

Gore declined to take questions from reporters.

Anderson, along with Denver Mayor John Hickenlooper, offered strategies for reducing greenhouse gasses, such as carbon dioxide and methane.

Most of today will be a kind of how-to tool kit on promising programs, including ideas from Seattle Mayor Greg Nickels, Chicago Mayor Richard Daley and such businesses as the Salt Lake City-based Squatters Pub Brewery.

The session Monday, "Why You Should Care," showed mayors the links between big-picture issues of climate change - the melting Arctic and rising sea levels - and local problems, like flooding, drought and disease.

Climate researcher and Weather Channel reporter Heidi Cullen talked about the increase in "extreme weather events" that occur with increasing frequency as result of climate change.

She said the number of 90-plus-degree days and water shortages is growing fast and that statistics suggest that by mid-century, every other summer may be hotter than the summer of 2003, Utah's hottest ever.

Paul Epstein of the Harvard School of Public Health told how rising temperatures also contribute to infectious disease and even allergies. Studies have shown, he said, that when the amount of carbon dioxide in the air is doubled, ragweed generates 60 times more pollen.

fahys@sltrib.com