The focus on consumption makes sense. Understanding its impact on climate change is a necessary first step for families, and municipalities, to take concrete action to mitigate carbon emissions. This sort of recalculation, however, could have an unforeseen effect on the international politics of climate change by shifting responsibility on a global scale.

With the concentration of carbon dioxide in the air zooming last spring to its highest level since mastodons roamed the earth some three million years ago, the United Nations, against all odds, hopes 2014 will finally deliver the breakthroughs needed for the big carbon-spewing nations to agree on a plan by 2015.

“I challenge you to bring to the summit bold pledges,” urged the United Nations secretary Ban Ki-moon, as he invited global leaders to a nuts-and-bolts horse-trading meeting in New York next September.

The diplomacy of climate change appears as stuck as ever. Poor carbon-spewers like China justify their opposition to tight carbon limits on the grounds that, on a per-person basis, their emissions are still very low. Moreover, most of the carbon in the atmosphere now, they argue, was put there by Americans and other wealthy carbon-spewers, who burned a lot of fossil fuels on the way to getting rich. Forbidding the Chinese from doing the same would be tantamount to condemning them to stagnation.

Policy makers in Washington retort that while all this may be true, a deal that only required rich countries to limit emissions would be pointless: their carbon savings would be negated by growing emissions elsewhere. Heavy emitters of greenhouse gases — like the agriculture and chemical industry — would decamp from rich nations to the less carbon-restricted shores of the developing world.

Indeed, recent research suggested that if rich countries were to cut emissions by 20 percent from 2004 levels without securing cooperation from developing countries, some 5 to 19 percent of the carbon savings would be lost to “leakage.”

Even more troubling, there is nowhere near a consensus on who is responsible for historical emissions. Some studies have concluded that the rich world put up to 80 percent of the existing carbon dioxide in the air. But this year researchers in the Netherlands and at the European Commission concluded that by including the impact of changing land use, developing countries actually accounted for nearly half of all heat-trapping gases emitted between 1850 and 2010.