It was a motley group that gathered Wednesday for the Second Annual Nelson Institute Earth Day Conference at the Monona Terrace: scientists, urban planners, transportation experts, public health advocates and educators; 400 people in all maxed out the conference’s registration limit.

While the conference as a whole focused on solutions to the environmental and economic impacts of climate change in Wisconsin, the keynote speech in the morning tackled the “uncertainty” of climate change predictions and what this actually means.

When scientists say they’re uncertain about projections from their climate change models, skeptics use it unfairly as a reason to discount all climate change science or at least downplay potential risks, according to keynote speaker Jay Gulledge, senior scientist at the Pew Center on Global Climate Change.

In her introductory comments, Tia Nelson blamed the press for promoting climate change skepticism when they give skeptics equal play in news stories: “The press have done a stunning job of promoting ignorance and a false sense of uncertainty about the climate change science.” She is the daughter of Gaylord Nelson, after whom the Nelson Institute is named. He was a longtime Wisconsin governor and senator and founded Earth Day in 1970.

Of 900 peer-reviewed studies published in a 10 year period, she added, all concluded that climate change is a dire problem and a direct result of human activity. During that same time, 52% of 600 news articles about climate change gave equal space to skeptics or deniers.

Gulledge spent much of his 40-minute talk explaining why "uncertainty" in scientific predictions should not provoke apathy. In fact, there is more reason than ever now to believe that recent predictions are too conservative, he said. In 2001, studies predicted that the polar caps would start melting in about 100 years. In 2007, scientists discovered they were already melting and doing so at an alarming rate.

When scientists are unsure about a model’s accuracy, the uncertainty is not about whether or not the trend will take place but about how severe the trend will be.

"The fact that it’s uncertain doesn’t mean that it’s not risky. Things can happen in a nonlinear way. (Scientists) seem to be systematically underestimating rates of change. We also see that the likelihood of severe catastrophic outcomes is actually significantly higher than we’ve been thinking that it is, based on the latest science," he said.

Towards the end of his talk, he showed the audience a chart that calculated uncertainty into a line on a graph. "This is how our uncertainty looks right now. It’s not a nebulous unknown. It has a shape, and it says that there’s some unacceptable probability that it’s going to be worse than we thought," he said

Gulledge backed himself up with bleak statistics, presented in a matter-of-fact, calm voice.

For one, he said that across the Midwest, "more frequent, hotter and longer" heat waves will debilitate northern cities ill-equipped to deal with prolonged and intense heat. On the coasts, cities at sea level are threatened by oceans that he said will possibly rise five feet by 2100. (Editors Note April 21, 2008, 10:38 a.m.: Corrections were made to an earlier version of this article. The article originally misquoted Gulledge's rising sea level predictions.)

He ended his talk with a boxing anecdote. "In 1973, George Foreman knocked out Joe Frazier, who was thought to be unknockable-outable," he said, and put this quote from a Red Smith article in The New York Times up on his PowerPoint screen:

“Frazier blamed his pride. He said he hadn't realized how strong Foreman was, should have tried to bob and move away but ‘my pride wouldn't let me.’ After the second knockdown, Joe said, the challenger simply overpowered him.”

“Now, my point is,” he continued, “we’ve got to get ahead of this problem. We can’t let misconceptions and pride get in the way, or we will be knocked out.”