Last week, the National Snow and Ice Data Center, in Boulder, Colorado, announced that the Arctic sea ice had reached a new low. The sea ice shrinks in the summer and grows again during winter’s long polar night. It usually reaches its minimum extent in mid-September. On September 16, 2012, the N.S.I.D.C. reported, the sea ice covered 1.3 million square miles. This was just half of its average extent during the nineteen-eighties and nineties, and nearly twenty per cent less than its extent in 2007, the previous record-low year.

It would be difficult to overstate the significance of this development. We are now seeing changes occur in a matter of years that, in the normal geological scheme of things, should take thousands, even millions of times longer than that. On the basis of the 2012 melt season, one of the world’s leading experts on the Arctic ice cap, Peter Wadhams, of Cambridge University, has predicted that the Arctic Ocean will be entirely ice-free in summer by 2016. Since open water absorbs sunlight, while ice tends to reflect it, this will accelerate global warming. Meanwhile, recent research suggests that the melting of the Arctic ice cap will have, and indeed is probably already having, a profound effect on the U.S. and Europe, making extreme weather events much more likely. As Jennifer Francis, a scientist at Rutgers, observed recently in a conference call with reporters, the loss of sea ice changes the dynamics of the entire system: “It’s like having a new energy source for the atmosphere.”

Yet, as big as the almost certainly irreversible retreat of the sea ice will figure in the future of the planet, it has attracted relatively little attention in the here and now. A study released on Thursday by Media Matters for America, a liberal watchdog group, found that over the last few months, Representative Paul Ryan’s fitness routine—he’s a big fan of what’s known as the P90X workout plan—has received three times as much television coverage as the ice loss.

“What’s hotter: Global warming or Paul Ryan’s abs?” the study asked.

Which brings us to the Presidential campaign. You might have thought that with the Arctic melting, the U.S. in the midst of what will almost certainly be the warmest year on record, and more than sixty per cent of the lower forty-eight states experiencing “moderate to exceptional” drought, at least one of the candidates would feel compelled to speak out about the issue. If that’s the case, though, you probably live in a different country. Remarkably—or, really, by this point, predictably—the only times Mitt Romney has brought up the topic of climate change, it has been to mock President Obama for claiming, back in 2008, that he was going to try to do something about it.

“President Obama promised to begin to slow the rise of the oceans,” Romney declared in his convention speech in Tampa, pausing here to give the audience time to chuckle, “and to heal the planet. My promise is to help you and your family.” He liked this line so much that he repeated it a week or so later on “Meet the Press,” saying “I’m not in this race to slow the rise of the oceans or to heal the planet. I’m in this race to help the American people.” Obama at least got exercised enough to point out, in his convention speech, that “climate change is not a hoax.”

“More droughts and floods and wildfires are not a joke,” he said. “They are a threat to our children’s future.” But that was as far as he was willing to go: no more grandiose claims about actually taking action. Two groups, Forecast the Facts and Friends of the Earth Action, recently teamed up to launch a Web site, climatesilence.org, whose home page shows photos of Romney and Obama with duct tape over their mouths. “The presidential candidates are silent on the essential facts of climate change,” the group observes.

Next week, Romney and Obama will meet for their first debate, in Denver. There’s no particular reason to believe that they will be asked about climate change, but here’s hoping—because by the time of the 2016 debates, the Arctic sea ice may already be history.

Image of the Arctic sea ice on September 16, 2012, the day that the National Snow and Ice Data Center identified to be the minimum reached in 2012, with a yellow outline showing the average sea-ice minimum from 1979 through 2010. Courtesy of NASA/Goddard Scientific Visualization Studio.