Starting in 2007, carbon dioxide emissions in the U.S. began dropping off and by 2013 had been cut by 11 percent.
Many have attributed the drop in CO2 to the switch from coal to natural gas to generate electricity, as natural gas production in the U.S. ramped up thanks to new fracking technologies. Even TreeHugger reported on a Harvard study that suggested a correlation between lower gas prices and a drop in CO2.
But a new study from researchers at the University of Maryland suggests that the economic recession was a bigger driver in the drop in carbon emissions. The study, published in Nature Communications, compares various factors that contributed to the decreased emissions.
Burning natural gas does have lower emissions than coal, and between 2007 and 2012 the percent of coal-power electricity in the U.S. dropped from 50 percent to 37 percent. Much of that was replaced by natural gas, but also by renewables. The researchers say that the switch to gas is only a minor diver of the CO2 decline.
A much more important driver is the level of consumption, or GDP per capita. The researchers found that the sharpest decline in CO2 happened during the worst of the recession, between 2007 and 2009. During that time, they calculate that 83 percent of the decrease is due to economic factors like consumption and production. As the economy started to recover after 2009, emissions crept back up.
The findings have implications in a number of ways. First, we need good data about what factors change greenhouse gas emissions if we want to fight climate change. Real world data like the emission drop following the recession can be valuable information for future policy choices, if we interpret it correctly.
Secondly, it shows what a big impact consumption patterns have on emissions. "We need to rethink the amount of stuff that people are consuming," author Klaus Hubacek told BBC news. "One could also tax the dirty stuff, one could think of a tax on more polluting items, driven by environmental reasoning."
Finally, the study suggests that natural gas doesn’t represent the easy carbon-cutting solution it may seem to be, either in the U.S. or in other parts of the world. The researchers say that focusing on gas extraction may limit the growth of renewable energy sources with carbon neutral emissions, such as solar and wind.
Laixiang Sun, another of the paper’s authors, said that sustaining economic growth while continuing to reduce greenhouse gas emission will require decreases in energy intensity as well as “radical decarbonization.”