The U.S. Energy Information Administration (EIA) recently announced the good news that CO₂ emissions in the country dropped by 2.4% in 2011 from the 2010 level, which had the biggest increase of any year during the decade.

(Source: EIA)

EIA attributes this decline to weakening economic growth, with an increase in U.S. GDP of only 1.8% in 2011, compared to the 2.4% growth in 2010.  The correlation between the economic activity in a nation and its carbon output is usually very strong – the slower the economic production, which to a great extent relies on fossil fuels for energy, the lower greenhouse gas (GHG) emissions.

Another reason has been the weather.  Although the country experienced the 2^nd hottest summer on record last year, that resulted in only a modest increase in consumption of electricity for cooling, but because of the relatively mild winter across a large part of the country, the demand for energy to heat homes and buildings declined significantly.  The net result was a decrease in energy consumption, especially in the residential sector.

A third contributing factor is changing fuel prices and consumption.  While the national average price of gasoline remained at more than $3 per gallon throughout the entire year, representing an increase of 27%, there was a subsequent drop of 1.2% in the numbers of miles travelled by cars. According to the EIA, this resulted in a 1.4% drop in energy use in the transportation sector, thus lower carbon emissions, in 2011.

Most noteworthy, though, is the increasing power generation from wind, solar, and other renewables, including hydroelectricity.  With respect to wind power, Pike Research has forecast that a total of 5,784 megawatts (MW) of wind capacity was installed in North America in 2010, accounting for more than 22% of the world’s total installed wind generation.  Increased reliance on natural gas – the least carbon-intensive of the fossil fuels – along with a 6% decline in coal generation (which produces the highest level of CO₂) has also contributed.

With the continued push for renewable power and natural gas to meet the demand for electricity – and, perhaps, a still-stagnant economy – carbon emissions are likely to drop further in the coming years.  Who knows, one day the United States might no longer be one of the worst carbon emitters in the world.