Hundreds of global warming skeptics are in Washington to hear attacks on mainstream climate science and responses to it, like renewable energy programs and federal initiatives to reduce greenhouse gas emissions.

For Geofrey Greenleaf, the Heartland Institute's conference is an opportunity to gather compelling details to be used against climate change believers during political discussions in the Cleveland area, where he works as an investment adviser.

"You basically can't discuss this in polite cocktail society because everyone knows global warming is here and growing," Greenleaf said. "I'd like to have more ammunition."

But Greenleaf and others at the conference evade common conceptions applied to climate doubters. The degree of skepticism expressed at the conference ranges from downright denial to a belief that humans are modestly contributing to climate change. The question is by how much.

"I think there's anthropogenic global warming to some extent," Greenleaf said. "But what we don't know is if it's 90 percent or 10 percent."

He has a feeling that it's closer to the lower number.

The view that climate change is occurring, to some degree, also surfaced frequently among speakers yesterday.

Applause for 'moderate' climate regulation

One acknowledged that rainfall was getting a bit heavier and that heat waves are on the rise. But the speaker, Patrick Michaels, a senior fellow at George Mason University and the author of a new book promoting skepticism, said the changes are too mild to justify a major global response.

Humans are affecting the climate somewhat, he said, "But it's not the end of the world."

Meanwhile, Robert Mendelsohn, an economist at Yale University, told the conference of free market conservatives that some mild government interaction is needed to prevent financial damages from future climate effects. He argued that the effects of greenhouse gases are too obvious to ignore, though the alarmism of many environmentalists is overblown.

"You really want to be thinking about moderate rates of regulation -- cheap things," Mendelsohn said, pointing to the European cap and trade system as an example. "We do know enough about the science that we do want to begin to regulate. The world needs to get started."

He was not booed off the stage. The crowd even applauded his presentation.

To be sure, there were heavy attacks on climate scientists and their findings. And the majority of speakers yesterday denigrated public policies addressing climate change as an expensive fiasco pursued by liberal ideologues. The failure of cap and trade to pass Congress was mentioned repeatedly, and some argued that renewable energies like wind and solar were impotent and too costly.

Cape Wind, the permitted offshore wind project proposed in Massachusetts, is a "huge fetish symbol" of liberal politicians, said David Tuerck, an economist at Suffolk University.

"We're talking about preparing for centuries ahead," he said of climate policies, using a timeline that advocates for action dispute. "We're doing that in a world environment where we can't even get a couple countries together to knock off a tinhorn dictator in Libya. So with that in mind, I'm not optimistic about the value of investing anything at all in the pursuit of renewable energy right now."

'The bias is just so extreme'

Others seriously questioned whether the world's community of climate scientists is caught in a cyclone of self-promotion, driven by the pressure to validate past findings and to receive federal grants.

"If a [scientist] sends in a paper [for publication] that says it's not the end of the world, I guarantee you the reviewers feel threatened, and that they will give it the most difficult review possible," said Michaels, "This is just human nature. It's not a conspiracy."

But those assertions have not been proven. The email controversy from late 2009 termed "Climategate" roused sharp criticism from opponents, but investigations cleared the scientists involved and didn't diminish the scientific underpinnings of climate change.

"There is no scientific body of national or international standing that rejects the findings of human-induced effects on climate," Peter Gleick, a scientist and president of the Pacific Institute, an environmental group, said on a conference call on Wednesday. "There's plenty of science to do, but the fundamentals are very strong."

The conference was attended by dedicated listeners, some of whom scratched notes on pads, took pictures of presentation slides, and nodded in agreement.

George Mears, a former navy flier who tracked hurricanes, believes scientists are manipulating the temperature record by using data from weather stations near "heat sinks" like parking lots, buildings and other infrastructure.

"The bias is just so extreme that it makes you angry," said Mears, who believes it's up to scientists to set the record straight for politicians, who are "basically dumb."

He's politically active in the Norfolk, Va., area, where he promotes limited government and fiscal restraint. He opposes things like light rail and all the "green crap."

Skeptic: Let's talk in 30 years

While debate flared around what to do about climate change, the notion that the earth is warming might be more widely accepted.

The main event yesterday was a lunchtime debate between two scientists. But their positions varied by the degree to which the temperatures on Earth might rise.

Roy Spencer, a climate scientist at the University of Alabama who argued from the skeptical side, agrees that human contributed carbon dioxide lessens the planet's ability to shed heat, meaning that warming is likely.

"For the most part I agree with the [Intergovernmental Panel on Climate Change], that adding CO2 to the atmosphere will cause some warming," Spencer said, adding that the temperature rise will be much less than the panel predicts.

The odds of him changing his mind to promote aggressive steps to stanch emissions is unlikely to occur anytime soon.

He'll believe in the brand of climate change that mainstream scientists warn of if temperatures rapidly rise for another 30 years, he said.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500