Reducing global carbon dioxide emissions will be an even more daunting challenge than we have been led to believe, according to a sobering commentary in the April 3 issue of Nature magazine.

The piece, titled “Dangerous Assumptions,” confirms the thesis of an article in the first issue of Miller-McCune magazine: That the difficulty of getting a handle on climate change has been widely underestimated.

Lead author of the commentary is Roger Pielke Jr., a professor of environmental studies at the University of Colorado. He and his colleagues argue that positive assumptions built into the most recent estimates by the Nobel-winning Intergovernmental Panel on Climate Change – that new technologies will result in dramatic reductions in the growth of future emissions – are overly optimistic.

“According to the IPCC report, the majority of the emission reductions required to stabilize CO² concentrations are assumed to occur automatically (as technology improves and industry moves to using more efficient energy sources),” Pielke said. “Not only is this reduction unlikely to happen under our current policies, we are moving in the opposite direction right now.

“We believe these kind of assumptions in the analysis blind us to reality and could potentially distort our ability to develop effective policies.”

Defenders of the IPCC’s assumptions argue they are in line with historical averages. Energy efficiency has improved by more than 1 percent per year during the first three decades, which makes the IPCC estimate of 0.6 percent increases per year seem quite achievable.

On the other hand, energy efficiency has actually decreased during this decade, thanks in large part by the increased use of cheap, “dirty” energy sources such as coal in China. Optimists call that a temporary shift, and insist developing nations will ultimately segue into using cleaner, more efficient energy sources.

Perhaps, Pielke and his colleagues answer, but the IPCC is playing “a risky game” in assuming this will happen rather than actively promoting it.

“There is no question whether technological innovation is needed – it is,” they write. “The question is, to what degree should policy focus explicitly on motivating such innovation?”