Emissions figures are in million tons of carbon; for tons of CO2, multiply by 44/12. Source: Compiled by Earth Policy Institute with 1950-1993 from "Carbon Dioxide Emissions from Energy Consumption by Source, 1949-2011," Table 11.1 in U.S. (Brian McGill)Between 2007 and 2011, the amount of carbon dioxide the United States spewed into the air decreased by 2 million tons, or 11 percent. Accounting for part of the decrease, explains the Earth Policy Institute, is the recession. When the economy slows, carbon emissions slow with it. But our habits have changed as well, and in the past few years America really has gotten "greener."
Cars have become more efficient, and emissions from oil are down about 100 million tons since the middle of the last decade. We're also driving less — national miles driven peaked in 2007. Now, the Earth Policy Institute explains, "more cars stay parked because more people live in urban areas, opt for public transit, work remotely, or retire and thus no longer commute to work." Factor in the decline of coal power, and the small but significant rise of wind energy, and the U.S. is 11 percent greener than it was just a few years ago.
And this happened, more or less, without a concerted federal effort. "U.S. carbon emissions have declined at an impressive rate given the absence of any cohesive federal climate-change policy," the Yale Forum on Climate Change explains. "The U.S. has actually managed to make significant progress toward its long-abandoned Kyoto Protocol target to reduce emissions 7 percent below 1990 levels."
Granted, even though the levels have dropped, carbon dioxide continues to accumulate in the atmosphere. There is certainly more CO2 in the air today than there was in 2007 (and while the U.S. is a major source of greenhouse gas emissions — about 16 percent — it certainly isn't the only one).
But this is a promising trend considering recent research from the journal Nature that predicts when climate change will have fundamentally altered local climates. The study spells out two diverging scenarios for Earth. One is business as usual, in which cities like Washington and New York will have a radically altered climate (diverging from long-historical norms) by 2047. But if we significantly reduce the amount of carbon emissions, that date could stretch to 2072.
The developed nations of the world will have to lead the way, the report concludes, as the first countries to feel the impacts of climate change will be poorer nations in tropical climates. The authors write:
... any progress to decrease the rate of ongoing climate change will require a bigger commitment from developed countries to decrease their emissions but will also require more extensive funding of social and conservation programs in developing countries to minimize the impacts of climate change. Our results on the projected timing of climate departure from recent variability shed light on the urgency of mitigating greenhouse-gas emissions if widespread changes in global biodiversity and human societies are to be prevented.