Climate change played a key role in that record, just as it has pushed up temperatures around the world. Globally, we've now experienced more than 330 months in a row of above-average temperatures.
That news puts President Obama on the hot seat. As his second term begins, the president has a clear opportunity to revolutionize his whole approach to fighting manmade climate change. And 2012 couldn't have made a more powerful case for urgent action against the greenhouse gas pollution creating this problem.
It wasn't just the heat: 2012 also bedeviled us with chaotic weather. Climate change, research shows, is driving up the risk of extreme weather like this summer's devastating drought, which affected more than half the country, and adding destructive power to storms like Hurricane Sandy.
As a scientist, I'm deeply concerned that 2012's blazing temperatures are just a taste of what lies ahead. America's future will be full of extreme heat, with growing risks of drought and food scarcity, according to the draft National Climate Assessment, a new report from more than 300 government scientists and outside experts. Within decades, some states will suffer a doubling of days hotter than 95 degrees.
Our weather is also likely to become more chaotic and destructive. Profound changes taking place in the Arctic are feeding North America's risk of extreme weather, in part by changing the jet stream. Arctic sea-ice extent hit a record low last summer, and the region's snow cover has begun shrinking faster over the past decade, according to a recent study.
What can be done? It's true, of course, that a divided Congress may stall legislative progress on climate change. But the good news is that the president need not wait on recalcitrant legislators.
Starting tomorrow, without any new laws in place, Obama's Environmental Protection Agency could begin making full use of the Clean Air Act against greenhouse gas pollution. Signed into law by President Nixon, this landmark law has proven itself over four decades by achieving huge reductions in dangerous pollutants like airborne lead.
The EPA has slowly begun applying the Clean Air Act to carbon-dioxide pollution - but progress has been modest, to say the least. Airplanes' carbon emissions, for example, have not yet been regulated. Nor has the massive greenhouse pollution from existing power plants.
The president must change that, because the next four years will be absolutely critical. Since carbon dioxide can linger in the atmosphere for thousands of years, we're running out of time to head off climate change's worst effects, according to the respected International Energy Agency.
Sometimes it seems that President Obama gets it. As a parent, I appreciated his election-night acceptance speech in which he spoke powerfully about the legacy we'll leave to future generations. We all, he said, want our children to live in an America that "that isn't threatened by the destructive power of a warming planet."
But as the president begins another four years in office, those soaring words must be matched by new action. Otherwise, we'll likely look back on 2012 as a year when we raced past numerous warning signs as we sped off the climate cliff.
ABOUT THE WRITER
Shaye Wolf is climate science director at the Center for Biological Diversity.
McClatchy-Tribune did not subsidize the writing of this column; the opinions are those of the writer and do not necessarily represent the views of McClatchy-Tribune or its editors.