For the past 12 years, Pekarek has read everything he can find about climate change.

His conclusion � that the Earth has been getting warmer, but humans aren't causing it � puts him at odds with mainstream public opinion and much of the scientific community.

None of that seems to faze Pekarek, who keeps a sign in his office that reads, "Geologists own climate history."

Just because there appears to be a consensus among scientists that humans are causing climate change by producing greenhouse gases such as carbon dioxide doesn't make it true, Pekarek said. Four hundred years ago, there was a consensus that the Earth was flat, he said.

"Climate is a very complex system, and anyone who claims we know all there is to know about it, let's say, is charitably misinformed or chooses to be," Pekarek said. "We fool ourselves if we think we have a sufficiently well-understood model of the climate that we can really predict. We can't."

Pekarek's theory is that the warming effect is caused by solar activity such as sun spots, which affect cloud cover. Pekarek believes solar activity is decreasing and the Earth will enter a cooling period within the next few years � even if humans keep pumping more carbon dioxide into the atmosphere.

"That's the grand experiment," he said. "Give me five or 10 years and I'll have the answer."