BOULDER - Environmentalist and author Bill McKibben, one of the most prominent and controversial voices in the environmental movement, is scheduled to speak Sunday at a sold-out event at the University of Colorado.

McKibben will speak at 7 p.m. at the Glenn Miller Ballroom as part of the Do the Math tour. The goal of the event - which organizers are expecting about 1,100 people to attend - is to increase awareness of how imminent catastrophic climate change is, said Micah Parkin, Colorado and regional director of 350.org. 350Colorado is organizing the event.

The tour also seeks to organize action against fossil-fuel companies and investors.

One of the premises of the tour is that fossil-fuel companies have plans to extract and burn more than five times the amount of carbon dioxide that can be used without raising the global temperature by more than two degrees Celsius. Almost 200 nations, including the United States, have committed to try to limit temperature increases to that amount, but McKibben believes oil and gas companies are working to undermine the commitment.

"Basically, he'll talk about how the fossil-fuel industry, because they are planning to burn all that carbon, is positioning itself as a rogue industry that will lead us over a cliff," Parkin said.

The tour seeks to organize opposition to the fossil-fuel industry, Parkin said. It also aims to build support for a campaign to persuade universities, religious organizations and pension funds to freeze investment in fossil-fuel companies and divest their stock. Activists are trying to get the University of Colorado to make that commitment.

McKibben is a thorn in the side of both industry and politicians in both major parties. He helps to lead the ongoing effort to block construction of the Keystone XL pipeline, which would carry oil from Alberta to refineries in the United States. McKibben was arrested last year at a protest outside the White House; those protests are credited with persuading the Obama administration to delay approving or rejecting permits for the project until 2013.

Parkin does not know if McKibben will address the effort in Boulder to create its own municipal utility. He has praised the effort in past visits to Boulder.

"It's exciting to hear that Boulder is taking firm control of its own energy destiny," McKibben said last year. "It's something we're going to have to do all over the country to have any hope of dealing with our carbon mess."

Do the Math tour organizers have set up an additional site on the CU campus to view a broadcast of the event, Parkin said. They also are working to set up additional watch parties in Boulder and around the state, she said.

People interested in attending a broadcast of the event can visit 350.org's website, Colorado350.org.

McKibben is the author of several books including "Eaarth: Making a Life on a Tough New Planet" and "The End of Nature."