As President Barack Obama brought up his interest in addressing global warming, a Texas congressman said U.S. emissions of greenhouse gases, widely believed to be fueling climate change, are on the decline.
"DID YOU KNOW?" Rep. Joe Barton, R-Arlington, wrote on Twitter during Obama’s Feb. 12, 2013, State of the Union address. "U.S. GHG emissions are at 20-year lows while global emissions are rising."
Global emissions have been on the upswing. The Environmental Protection Agency says on a web page that global carbon emissions from the burning of fossil fuels "increased by over 16 times between 1900 and 2008 and by about 1.5 times between 1990 and 2008." Separately, the government’s Carbon Dioxide Information Analysis Center contributed to a December 2012 "discussion paper" stating that in 2011, estimated global carbon dioxide emissions due to burning fossil fuels and making cement were up 3 percent from 2010.
We checked on Barton’s claim that domestic greenhouse gas emissions are at a 20-year low.
By email, Barton spokesman Sean Brown pointed out an August 2012 web post by the U.S. Energy Information Administration stating that estimated U.S. carbon dioxide emissions resulting from energy use during the first three months of 2012 "were the lowest in two decades for any January-March period." Brown also noted the Environmental Protection Agency saying in an online chart that as of 2010, concentrations of five common air pollutants--carbon monoxide, ozone, lead, nitrogen dioxide and sulfur dioxide--had decreased from 30 years earlier.
This information did not speak to all greenhouse gases, as Barton had, but carbon dioxide from burning fossil fuels is the largest contributor to greenhouse gas emissions.
Perry Lindstrom, an economist with the Energy Information Administration, emailed us a spreadsheet indicating that the nation’s energy-related carbon dioxide emissions were estimated at 1,339 million metric tons in the first quarter of 1992 and at a slightly higher amount, 1,344 million metric tons, for the comparable months of 2012. In the intervening years, first-quarter emissions topped out at 1,580 million metric tons in 2004 and bottomed out at 1,364 million metric tons in 1993, according to the spreadsheet.
Then again, the first quarter of 2012 was unusual, the agency said in its post. "Normally," the agency wrote, carbon dioxide "emissions during the year are highest in the first quarter because of strong demand for heat produced by fossil fuels." But such emissions were lower at the start of 2012 thanks to a mild winter, which reduced heating demand and energy use, the agency said, with other factors including a decline in coal-fired electricity generation, due largely to low natural gas prices, and reduced gasoline demand.
Still, the 2012 first-quarter emissions were lower than they had been in the first part of the year in 19 years. However, Lindstrom said by telephone, he would hesitate to reach conclusions solely by comparing emissions in part of a year to emissions in part of another year in contrast to looking, say, decade to decade. At our request, he provided a spreadsheet comparing energy-related carbon dioxide emissions for the 10 months through October 2012 to such emissions over the comparable part of each previous year over two decades. Our thinking was that this would deliver a longer view based on the latest information available when Barton tweeted. And according to this spreadsheet, the estimated emissions from January through October 2012, 4,386 metric tons, were the lowest 10-month total since 1995--17 years earlier--when such emissions totaled 4,385 metric tons.
Going forward, Lindstrom pointed out, his agency projects U.S. energy-related carbon dioxide emissions to remain below 2005 levels through 2040. Jim Butler, director of global monitoring at the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory, said by phone that such levelling out makes sense due to improvements in energy efficiency and shifts to fuel sources with less of a carbon footprint than coal.
Mindful that Barton’s tweet said greenhouse gas emissions were at a 20-year low, we looked next at emissions of methane, nitrous dioxide, sulfur dioxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride as estimated in the Environmental Protection Agency’s April 2012 inventory of U.S. greenhouse gas emissions--the latest inventory that would have been available when Barton tweeted. (The agency’s 2013 "draft inventory" was posted online Feb. 22, 2013.)
The 2012 inventory indicates that total emissions of three gases were higher in 2010 than 1990, while emissions of four others were lower.
In keeping with Barton’s 20-year window, we used the inventory figures to gauge the difference between estimated emissions of each greenhouse gas in 2010 and 1990:
--Carbon dioxide emissions in 2010 were 12 percent greater than in 1990;
--Methane emissions were lower by 0.3 percent;
--Nitrous oxide emissions were lower by 3 percent;
--Hydrofluorocarbon emissions were higher by more than 200 percent;
--Perfluorocarbons were lower by 73 percent;
--Sulfur hexafluoride emissions were lower by 57 percent.
Taking all the greenhouse gases into account, according to the inventory, overall emissions were 11 percent higher in 2010 than 1990--and also up 3 percent from 2009, when total emissions dipped considerably during the national recession. Aside from 2009, the previous year with lower greenhouse gas emissions than 2010 was 1997, according to the inventory.
The congressman said domestic greenhouse gas emissions are at a 20-year low.
This statement depends on a comparison of energy-related carbon dioxide emissions—not all greenhouse gases--over three unusually warm winter months of 2012 to such emissions in the same months of 1992. But the latest information available when Barton tweeted indicates that total U.S. greenhouse gas emissions were higher in 2010 than they were 20 years earlier, though the 2010 emissions were lower than they were 13 years earlier.
We rate this claim Mostly False.
CORRECTION, 10:42 a.m. April 8, 2013: Thanks to a reader's nudge, this story was amended to say that the discussed levels of carbon dioxide were in millions of metric tons, not metric tons alone. This did not affect our original rating of the claim.