Roy W. Spencer believes in global warming. He just thinks it's the Earth's fault. Climate debate can be hazardous, but this former NASA scientist is preeminently qualified to weigh in: In 1989 Spencer and colleague John Christy pioneered a method of measuring global atmosphere temperature using satellite microwave sensors, an achievement that earned awards from NASA and the American Meteorological Society. Today Spencer oversees a research team for an Earth-monitoring satellite from his office at the University of Alabama in Huntsville. In his spare time he writes books throwing cold water on the idea that global warming is mostly caused by people.

His latest, The Great Global Warming Blunder: How Mother Nature Fooled the World's Top Climate Scientists (Encounter Books, 2010), lays out Spencer's research into the effect of clouds on atmosphere temperature. Spencer became particularly interested in clouds when he learned about a key assumption climate modelers make when predicting future global warming: Warmer average temperatures will result in reduced cloud cover. What if that assumption had it backwards? What if reduced cloud cover were causing the warmer temperatures? "If you get that wrong," Spencer told me when I met him at a conference this summer, "then you get a totally wrong answer in terms of how much warming there will be as a result of us putting more greenhouse gases in the atmosphere."

With a full head of white hair and a kind demeanor, Spencer seems grandfatherly. And though his style in person isn't bombastic, his ideas are considered to be, and his outspokenness attracts friends and enemies. In 2006 Spencer launched a satirical environmental news website to poke fun at global warming alarmism with headlines like "EPA to Mandate Reductions in Emissions from Volcanoes." The alarmists shot back, calling Spencer a "disinformer," while radio host Rush Limbaugh calls Spencer the "official climatologist" of his talk show.

Spencer's outspokenness is grounded in peer-reviewed research showing that prevailing climate models could be confusing cause and effect when it comes to clouds and temperature. By only looking at the effect temperature has on clouds, the models can overlook the effect clouds have on temperature by blocking sunlight. These climate models, Spencer said, "reduce cloud cover when the climate warms, when they should be increasing cloud cover when the climate warms. And the difference between those two gives the difference between man-made global warming being barely measurable versus it becoming Al Gore's Armageddon."

This mistake results in an overly sensitive climate model that Spencer says punishes us when we add CO2 to the atmosphere. Research outcomes are important because battling the wrong causes of global warming—with things like taxes and research into alternative fuels—gets expensive.

If, as Spencer believes, the climate responds to global warming by attempting to reverse the trend (a negative feedback) rather than amplify it (positive feedback), it would imply that the warming of the last 30 to 50 years has been caused by mostly natural forces. It would also imply that future man-made global warming will be relatively small—a degree Fahrenheit or less in the next 50 to 100 years, says Spencer.

Even if human activity has played a role in 20th-century warming, Spencer believes factors besides carbon dioxide emissions are leading the change. In his new book he highlights several regional, ocean-based weather patterns that may, like El Niño and La Niña, be fueling atmosphere temperature changes. One is the Pacific Decadal Oscillation, an ocean and wind system that appears to change course every 30 years or so. Spencer thinks it could account for 75 percent of the observed warming of the last century. The cycle seems to have flipped again recently, and Spencer's gut feeling is that global warming will slow down or stop in the coming years. But he hastens to add—"I try not to make long-term predictions."

With research into natural agents of temperature change so incomplete, why have so many scientists taken sides to blame CO2? Spencer has several answers. First, everyone wants to be part of a science project that is going to help preserve the Earth or save mankind. Second, the UN body pushing the global effort to regulate greenhouse gases, the Intergovernmental Panel on Climate Change (IPCC), was originally created to build a case for man-made global warming: "In other words, the organization was not going to go out and look for alternative explanations. They were building the case for man-made global warming so that certain policy initiatives could be put into place— primarily the restriction or taxation of carbon-based fuels."

Yet another motive, Spencer believes, is religious conviction: "I find that virtually all scientists that work in earth science or in climate research have the impression that the climate system is fragile, that it's delicately balanced. This is a belief that has no scientific basis. In fact, 'delicate' doesn't mean anything scientifically. Yet those beliefs on the part of a research scientist can alter the direction that they go."

Even so, the meteorologist-turned-climatologist acknowledges that his own evangelical beliefs have predisposed him to follow an opposite path. "An advantage of having a biblical basis for the way I look at nature is that I consider the possibility that nature is actually pretty resilient," he said. "So when scientists had found what they thought were positive cloud feedbacks in the climate system, which would mean that the climate system is very sensitive, I questioned their assumptions, and I went back and looked at the details, and found that when you dig deeper, the truth is actually in the opposite direction to what they found."

Spencer continues to pursue that truth by sifting through technical data—right now he's investigating how much of 20th-century warming could be due to regional weather oscillations. But one hurdle for scientists like him is funding: "Out of the billions of dollars we put into climate change research, all of it goes into supporting the view that climate change is man-made, or assumes that climate change is man-made." All of Spencer's research grants have come from traditional government sources (not Exxon Mobil, as his detractors seem to believe), but his contracts are written in general enough terms to allow him to study natural methods of climate change.

Even after scientists like Spencer do research, it's another matter to publish it in mainstream science journals, where gatekeepers are sometimes unfriendly to alternative views on warming. "We've had a lot of peer reviewers over the years who have wanted to reject our papers when it was clear they did not even read the papers," he said. Once a reviewer didn't like his paper because it conflicted with the conclusions of the IPCC: "Even though I had been asked to write a paper looking at the other side of the issue—the view that the IPCC could be wrong—one of the reviewers of the paper said that I needed to change the paper to align it with the IPCC." Peer review is prone to bias, said Spencer, but it's the best system we have for now. "Scientists ignore what I do," he muses, which is often better than attacking it. And Spencer plans to continue propounding his unconventional global warming ideas—and research—to whoever will listen.

Email Daniel James Devine