You may have been encouraged to read a widely-circulated story last week that declared “CO2 Emissions in U.S. Drop to 20-year Low.” The report from the Associated Press largely credits cheap natural gas for the change, and says that “many of the world’s leading climate scientists didn’t see the drop coming, in large part because it happened as a result of market forces rather than direct government action.”
But is that really the full picture?
If you read the government report that is the basis for the Associated Press article, you’ll find some more nuance, as well as cause for both optimism and concern. The report by the Energy Information Administration (part of the Department of Energy), says that yes, energy-related CO2 levels are at their lowest levels in twenty years, if you’re looking at the first quarter 2012 compared to the same time periods in previous years.
But those are just first quarter results. If you look at year-over-year annual CO2 emissions (shown in a graph above), from a separate report released last week, the picture isn’t as rosy:
“After two years of declining carbon dioxide emissions (2008 and 2009) and one year of increasing emissions (2010), carbon dioxide emissions in 2011 fell, but at a less dramatic rate than in 2009. Unlike 2009, the 2011 decline occurred during a year of positive growth in the Gross Domestic Product (GDP). The 2011 decrease is only the fourth year since 1990 to experience a decline in carbon intensity of greater than 3.5 percent for the economy as a whole and only the sixth year since 1990 to experience an emissions decline.”
So, if you look at the annual data, greenhouse gas emissions are down, but not as dramatically as two years ago (which, the agency points out, happened during a recession). And annually, not anywhere near the levels of twenty years ago.
The agency also says that low natural gas prices leading to less coal-powered generation aren’t the only reason why energy-related carbon emissions are down. There was also:
- A mild winter that reduced household heating demand and therefore energy use
- Reduced gasoline demand
As everyone knows, this past winter was one of the warmest on record, and for much of the country, the warmest winter in forty years. That means less gas and coal being used to fire up power plants. “While generators used more natural gas for electricity generation,” the report says, “overall CO2 emissions from natural gas were down because of lower gas heating demand this winter when temperatures were significantly above the historical average for the season.”
The overall shift from coal to natural gas will help carbon emissions, but it may not be enough. Here’s why, according to Rachel Nuwer of the New York Times:
“Although natural gas is a more efficient fossil fuel than coal, burning it still produces carbon dioxide emissions. One of its strengths is that it produces more kilowatts of power than the equivalent amount of coal and it provides more energy for each carbon dioxide molecule emitted into the atmosphere. This so-called carbon efficiency is a crucial factor that allows scientists to project carbon dioxide emissions, with more efficient energy sources contributing less to climate change than the more inefficient sources.
Coal-fired electric power generation puts out about twice the amount of carbon dioxide — around 2,000 pounds for every megawatt hour generated — than electricity generated by burning natural gas. But that is still about 1,100 pounds per megawatt hour for electricity from natural gas. Scientists suggest the United States needs to reduce emissions to around 350 to 400 pounds per megawatt hour to stabilize atmospheric concentrations.”
The good news is that overall, even though the country is growing, our carbon is shrinking. The Energy Information Administration report found that in the U.S. last year, “carbon intensity” went down 4.2 percent. “Since 1990, energy-related carbon dioxide emissions in the United States have grown much more slowly than GDP,” the report says.
While the U.S. is emitting less carbon, that’s not the trend in other parts of the world. American exports of coal to places like India and China — which need more power for their growing populations and economies — are on track to set a new record. Even Germany is building coal plants as they move away from nuclear power. For the first half of 2012, coal shipments are 24 percent higher than during the same period last year, according to Bloomberg Businessweek.