BILL CLINTON declared last week that Americans “look like a joke’’ because leading Republican presidential contenders decline to embrace the agenda of the global-warming alarmists. Presumably he had in mind Texas Governor Rick Perry, who says that “global warming has been politicized’’ and calls claims of a decisive human role in climate change an unproven theory. “You can’t win the nomination of a major political party in the US,’’ fumed the former president, “unless you deny science?’’

To which Marc Morano, publisher of the irreverently skeptical website Climate Depot, promptly replied: “Bill is correct! No Democratic presidential candidate could get the nomination unless they deny the large role that natural variability plays in climate.’’

In truth, global-warming alarmism is not science at all - not in the way that electromagnetic radiation or the laws of planetary motion or molecular biology is science. Catastrophic climate change is an interpretation

of certain scientific data, an interpretation based on theories about the causes and effects of growing concentrations of carbon dioxide in the atmosphere. It is not “denying science’’ to have doubts about the correctness of that interpretation any more than it is “denying economics’’ to have doubts about the efficacy of Kenyesian pump-priming.

You don’t have to look far to see that impeccable scientific standards can go hand-in-hand with skepticism about global warming. Ivar Giaever, a 1973 Nobel laureate in physics, resigned this month as a fellow of the American Physical Society (APS) to protest the organization’s official position that evidence of manmade climate change is “incontrovertible’’ and cause for alarm. In an e-mail explaining his resignation, Giaever challenged the view that any scientific assertion is so sacred that it cannot be contested.

“In the APS it is OK to discuss whether the mass of the proton changes over time and how a multi-universe behaves,’’ Giaever wrote, incredulous, “but the evidence of global warming is incontrovertible?’’

Nor does Giaever share the society’s view that carbon emissions threaten “significant disruptions in the Earth’s physical and ecological systems, social systems, security, and human health.’’ In fact, the very concept of a “global’’ temperature is one he questions:

“The claim (how can you measure the average temperature of the whole earth for a whole year?) is that the temperature has changed from ~288.0 to ~288.8 degrees Kelvin in about 150 years, which (if true) means to me . . . that the temperature has been amazingly stable, and both human health and happiness have definitely improved in this “warming’ period.’’

By now, only ideologues and political propagandists insist that all reputable scientists agree on the human responsibility for climate change. Even within the American Physical Society, the editor of “Physics and Society’’ (an APS publication) has acknowledged that “there is a considerable presence within the scientific community of people who do not agree . . . that anthropogenic CO2 emissions are . . . primarily responsible for the global warming that has occurred since the Industrial Revolution.’’

Giaever is only one of many distinguished scientists who dissent from the alarmist view on climate change. Among the others are Richard Lindzen of MIT and John Christy of the University of Alabama at Huntsville, both noted climatologists; the eminent physicist Freeman Dyson of Princeton’s Institute for Advanced Study; and S. Fred Singer, professor emeritus of environmental science at the University of Virginia. As for the population of weather experts best known to the public - broadcast meteorologists - The New York Times reported last year that skepticism of the prevailing anthropogenic global-warming theory “appears to be widespread.’’

Such skepticism is not “anti-science.’’ Everything in science is subject to challenge; innumerable facts about the natural world have been discovered only by poking holes in once-dominant theories. And if that is true generally, how much more so is it true when it comes to something as vast as climate change? Researchers still have no way “to reliably discriminate between manmade warming and natural warming processes,’’ climate scientist Roy Spencer has written. “We cannot put the Earth in a laboratory and carry out experiments on it. There is only one global warming experiment, and we are all participating in it right now.’’

Someday the workings of climate change may be as well understood as plate tectonics or photosynthesis. Until then, different theories will compete, assumptions will be fought over, and scientific findings will be overstated by people with political or social agendas. We’ll know that the science really is settled when the battles have come to an end.

Jeff Jacoby can be reached at jacoby@globe.com. Follow him on Twitter @Jeff_Jacoby.

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