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As a Republican and a former climate change doubter, I can understand Republican Rep. Chris Stewart's reluctance to commit to strong action. ("Stewart Cautious on Climate Change," Opinion, April 13.)

However, I hope he soon goes on to study the issue enough to find out, as I did, that the scientific evidence very strongly supports the conclusion that we are taking a terrible risk by putting off such action, and no amount of nitpicking, straw-man argumentation or excuse-making will magically make that risk disappear.

His begins with a straw man — climate has changed naturally in the past, so the Earth has "no ideal temperature." Climate scientists never claimed any such thing. Instead, they warn that Earth's ecosystems and human civilizations are now adapted to a certain narrow temperature range, and rapid, sustained temperature change can make it difficult to adapt.

Stewart next claims that the science of climate change is "anything but settled" because none of the standard climate models is "reliable" for predicting things like the fact that "global temperatures [have] not risen in the past 15 years."

This is false. Global temperatures have risen over that period, but the trend is not "statistically significant," which isn't the same thing. And since the weather system is chaotic in the short term, current models can't accurately predict decade-to-decade fluctuations. All of them predict that there ought to be periods of several years with slower warming, but they disagree about when.

That's why scientists don't make projections based on any single model. They just project that temperatures should stay somewhere in the range that the suite of models predicts. And they have.

Science never provides absolute proof, so saying the science isn't completely "settled" is like saying the sky is blue. It's also true, however, that there can be so much evidence for a proposition that nearly all (but usually not 100 percent) of a scientific community will accept it.

Several lines of evidence, including multiple surveys of climate science experts and the peer-reviewed scientific literature on climate change, indicate that at most a few percent of the experts disagree with the consensus view that humans are mostly responsible for the climate change over the past half century. Stewart doesn't challenge this view with any competing study, He just nitpicks a single study and ignores the rest.

Finally, Stewart complains that climate action is expensive, and in any case, such measures wouldn't make much difference if China and India continue economic development.

Several economic forecasts show that the costs of doing nothing might be much higher, so again, Stewart is ignoring at least half the equation, but this morally bankrupt blame shifting ought to be beneath him. It's true that if only the United States does anything to reduce emissions, it won't help much. But when has Stewart ever supported any efforts to broker an emissions-reduction agreement with China, India and the rest of the world?

By the same logic, I could justify almost anything, because what one person does can't make a statistically significant difference in the state of the world. But if that one person (or nation) can influence others to follow suit, their actions can make a difference.

Stewart needs to decide whether he wants to be a person who makes a positive difference by trying to tackle a difficult problem, or just another politician who ignores most of the evidence for the existence of the problem and blames his inaction on others.

Barry Bickmore is an associate professor of geological sciences at Brigham Young University. He lives in Orem. The opinions expressed are his own and do not necessarily reflect official positions of his employer.