Dueling scientists made presentations Wednesday at the state Capitol to a packed legislative committee hearing on the science behind global warming, and the political divisiveness over whether it is significantly caused by humans.

First, members of the House Public Utilities and Technology Interim Committee heard from James Steenburgh, professor and chairman of the Department of Atmospheric Sciences at the University of Utah.

Steenburgh, while stressing he has never taken a "policy position" on climate change as a scientist, pointed to a survey that shows 97.4 percent of scientists consider human activity to have an impact on global warming.

Part of that consensus, he said, stems from the "preponderance of the evidence" and that any alternative explanation has failed to withstand rigorous scrutiny.

Roy Spencer, from the University of Alabama and a NASA scientist, said he doesn't dispute that climate change has occurred, and man has had some impact. But he said the larger question rests on the significance of that contribution to shifts in climates.

Spencer pointed out that the most accurate scientific data measuring certain factors related to global warming only go back nine years and "modelers" look for outcomes that support man-made global warming.

Over the last 2,000 years, "global warming and global cooling is the rule, not the exception. … There is evidence out there that Mother Nature by herself causes climate change."

Lawmakers and the public were talked through a variety of competing charts, conclusions and complex discussions about the data that goes into the modeling, and how the outcomes of the studies are interpreted — or not.

Rep. Lorie Fowlke, R-Orem, said the complexities and contradictions surrounding climate change are polarizing for policymakers.

"I can't express the frustration I have as a policymaker who is not a scientist how difficult it is for us to make policy decisions when the science has become so politicized," she said.

Afterward, Rep. Roger Barrus, R-Centerville, said he appreciated a presentation that focused on "what I consider balanced views and opinions from credible sources."

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