Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

Carbon dioxide emissions in the United States from the production and consumption of energy have been on the decline since about 2005, after generally being on the rise ever since our country was first founded.

The decline in emissions between 2012 and 2011 was 3.8 percent, which, according to the Energy Information Administration (EIA) was the largest decline in a non-recession year since 1990 and the first time that carbon dioxide (CO₂) emissions fell while the per capita economic output increased by more than 2 percent. In other words, we are producingmore while emitting less carbon dioxide.

The big player in 2012 was the continued switch from coal to natural gas for electrical generation. It is generally accepted that gas-fired generation results in about half as much carbon dioxide emissions per kilowatt-hour as coal-fired.

While some would glibly say this is a result of increased regulation of greenhouse gases, it’s much more just good-old economics and the profit motive that are responsible. Hydraulic fracturing, horizontal drilling, and inherently less expensive physical plants mean it is cheaper to produce electrical power from gas than from coal. In fact, as the figure below shows, there’s been pretty much a one-for-one switch between the two sources, with coal-fired down by 215 billion kilowatt-hours (kwh) and gas up by 212.

Despite the fact that “renewable” electricity generation declined in 2012, carbon dioxide emissions per kwh still went down, by 3.5 percent, thanks to the overwhelming effect of natural gas substitution. 

In 2012, the CO₂ reductions from the combination of a more energy-efficient economy and a lower carbon-intensity energy supply were larger than the combined increase in gross domestic output and growth in population.

One signature of greenhouse-effect driven climate change is that winters (and especially the lowest temperatures of winter) should warm preferentially to summers. According to the EIA, “much more energy is needed for space heating than for air conditioning” and the very warm winter of 2012 saved much more energy than was cost by the warmer-than-average summer. 

The combination of fuel switching, weather, and some incremental increase in vehicular fuel efficiency produced the largest drop in carbon intensity since 1949, the year the EIA data compilation begins. “Carbon intensity” is the emission of carbon dioxide associated with the production of a constant dollar of gross domestic product.

And while all of this should make President Obama happy as the U.S. carbon dioxide emissions decline is ahead of the pace needed to meet his goal of reducing emissions by 17 percent from 2005 levels by 2020, little of this is actually from his doing.

This means that the majority of it is being achieved without governmental interference. The fact is that capital is required for investment in technologies that produce things more efficiently (like new gas-fired power plants) or produce more efficient things (such as stingier gasoline engines and [maybe] hybrid cars, though life-cycle analyses of them are somewhat conflicting).

Which should make you wonder, why is the government intervening at all? We wonder the same thing.