Less than a month after a terrorist massacre of Parisian concertgoers and cafe patrons seemed to target modern civilization itself, the same city hosted a rare triumph of international order. Defying expectations depressed by repeated failures to reach a global climate accord - as well as the daunting complexity of the issue and competing interests involved - nearly 200 nations signed on to an agreement to limit global warming.

The countries agreed to reduce climate-changing emissions enough to keep the resulting average global temperature increase under 2 degrees Celsius, or 3.6 degrees Fahrenheit, about half of which has already taken place. Given that the agreement remains a general framework that does not specify consequences for failure to comply, it's far from clear whether the signatories will abide by their promises. And those promises, while ambitious in the context of long-standing global inaction, are modest considering the scope and imminence of the problem. The acknowledgment of the problem and the consensus for doing something about it nevertheless suggest a watershed moment.

It was strangely fitting that it came as the temperature in Philadelphia soared past 70 just a week before the winter solstice - though no local warm spell can be linked to global warming any more than a cold snap shows it's a hoax perpetrated on innocent fossil-fuel tycoons. But a balmy East Coast Christmas will at least delay further attempts to refute climate change by bringing a snowball onto the Senate floor, as Sen. Jim Inhofe (R., Okla.) did last winter, perplexing logically literate people everywhere.

The Paris pact repudiates those who have taken advantage of the intricacies of climate science to make such simpleminded arguments. Inhofian climate change denial is becoming the increasingly exclusive province of the United States - an especially dubious facet of American exceptionalism. If smogged-in Beijing and backward-oriented Saudi petrocrats can be corralled into agreeing that man-made warming poses a serious threat, then why, in the words of a famous Phillies fan, can't us?

Complementing the strenuous efforts of the Obama administration, the French, and environmental activists, a number of small island states - some of them, like the Caribbean nation of Antigua and Barbuda, well-known to American vacationers - played a disproportionately large role in the negotiations. Thanks to rising sea levels, their futures look about as auspicious as that of a snowball buffeted by the hot winds of the Senate.

As Hurricane Sandy showed, large parts of New Jersey, New York, and other populous coastlines have much the same problem. And yet American negotiators felt compelled to mount a last-ditch effort to save (and weaken) the agreement by replacing a single stray word, shall, with should, lest the deal take its nonexistent chances in Congress.

After Kyoto, Copenhagen, and many other unsuccessful summits - Paris was known as "COP21" because it was the 21st annual Conference of the Parties to the U.N. climate convention - international negotiators faced similar odds against significant accomplishment. That they beat them makes every snowball's chances look a little better.