Representatives of 194 nations who met in South Africa in December reached a last-minute agreement to sign a treaty to reduce greenhouse emissions. It was an imperfect conclusion at best: an agreement to have a binding agreement in place by 2020, a date many climate scientists consider too late to turn around the climate trends that are permanently endangering the earth.

Yet in 2009, the Congress came tantalizingly close to turning around those trends, when the then-Democratic-controlled House passed a bill that would have reduced emissions by 17 percent by 2020 and by more than 80 percent by 2050.

The bill failed to pass the Senate, Democrats lost control of the House in the 2010 elections, and Republicans began a campaign to erode public support for climate legislation. Any new legislation. or international agreement on emission reductions, will have to wait until the domestic political climate changes. It might take a while.

Consider how the issue is playing in the Republican presidential primary. “[Nancy Pelosi] is committed to her global-warming fanaticism to the point where she has said that she’s just trying to save the planet,” Michele Bachmann said after the cap-and-trade bill died. “We all know that someone did that over 2,000 years ago: They saved the planet. We didn’t need Nancy Pelosi to do that.” In a country founded by men shaped by the Enlightenment, how did our politics become so debased that an elected official can make such a statement and still be considered a viable candidate for the presidency?

Although she is now irrelevant to the primary, Bachmann is not an anomaly. Rick Santorum has argued that climate-change legislation is based on “junk science.” Ron Paul described the notion of an overheating planet as “a liberal hoax.” And, said Rick Perry in September, “The idea that we would put America’s economy at jeopardy based on scientific theory that’s not settled yet to me is just nonsense…. Just because you have a group of scientists that have stood up and said ‘Here is the fact,’ Galileo got outvoted for a spell.”

While it is hard to make any sense of the Texas governor’s reference to Galileo, the science regarding climate change is settled.

Among the organizations in the English-speaking world who agree that burning fossil fuels contributes to the earth’s warming are: the American Chemical Society, the American Geophysical Union, the American Institute of Physics, the American Meteorological Society, the American Coral Reef Society, the Australian Bureau of Meteorological and Oceanographic Society, the Canadian Foundation for Climate and Atmospheric Sciences, the Canadian Meteorological and Oceanographic Society, the Environmental Protection Agency, the European Geosciences Union, the Geological Society of America, the Geological Society of Australia, the International Union of Geodesy and Geographics, the National Center for Atmospheric Research, and the Royal Meteorological Society (U.K.).