Forget the global war on terror, there's another enemy that's threatening to take down the world — and it's invisible.

According to Bill McKibben, keynote speaker of the 13th annual Stegner Symposium hosted Saturday at the University of Utah, that enemy is carbon dioxide, and it's time to launch a full-scale campaign against the gas.

"The reality is that ... we have got to get going in a far more dynamic fashion than we have so far," McKibben said. "The only analogy, maybe, that shows the kind of progress we need and the speed with which we need to do it is ... what we did before World War II. In the course of a year we changed the economic system of this country to stop producing consumer goods and start producing the goods we needed to fight and win the war against fascism. If we're going to win the war against carbon ... then we're going to need that kind of level of engagement."

McKibben, a well-known author on the subject of climate change, announced Saturday that he is launching his own campaign to gather support in the fight against global warming and emphasized that the time to make a difference is running out.

McKibben launched a Web site, www.350.org, Saturday based on the latest recognized number of parts per million of carbon dioxide emissions that are the threshold to stop global warming. That number has changed three times in the past 20 years, McKibben said.

In 1989, it was generally thought that 550 ppm of carbon dioxide emissions was the threshold, McKibben said. Over time, that number changed to 450 ppm in 1995, and now it's 350 ppm. According to McKibben, current measurements show that the levels of carbon dioxide in the Earth's atmosphere are already at 385 ppm.

"We're coming to understand with what science is telling us that the magnitude and the pace of this change is coming at us much faster than we could have realized," McKibben said. "We're already out of whatever safe zone there is. We're out in the danger zone, and we're dodging bullets. ... We didn't know it. We used to think we had some more margin, we had some more room for improvement, we had another decade or two, but we don't. That's where we are now."

McKibben emphasized that it's possible to decrease the effects of carbon dioxide on the Earth's atmosphere by decreasing the amount of carbon dioxide emissions produced globally, but if those emissions aren't decreased by 2012, "then we may have pushed the Earth past the tipping point."

McKibben said he thinks it's important for people to be involved politically and participate in a global, social movement toward decreasing carbon emissions in order to affect change.

The crowded room of about 450 people who came to hear McKibben speak stood and applauded at the end of his speech as a show of support. Bringing about public change is part of the reason the Stegner Symposium takes place every year, said Lincoln Davies, associate professor of law at the U. who helped organize the symposium.

"I think people are concerned about these issues and how we can start solving these problems," Davies said. "We see, across the nation, a growing awareness of climate change and alternative energy. The question is how quickly that movement can grow."

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