Are US Carbon Emissions Really Down? Methane Leaks Cause for Concern
August 26, 2014
A headline that has appeared frequently in mainstream media of late informs us that, in an unexpected turn of good news, US carbon emissions are down to 20 year lows, due to increased use of natural gas in power generation.
My uneasiness with this formulation comes from increasing evidence that the extraction of Natural gas has a a downside – largely unaccounted-for leakage in the system of wells, pipelines and processors that deliver gas to consumers.
A study of abandoned oil and gas wells in Pennsylvania finds that the hundreds of thousands of such wells in the state may be leaking methane, suggesting that abandoned wells across the country could be a bigger source of climate changing greenhouse gases than previously thought.
The study by Mary Kang, a Princeton University scientist, looked at 19 wells and found that these oft-forgotten wells are leaking various amounts of methane. There are hundreds of thousands of such oil and gas wells, long abandoned and plugged, in Pennsylvania alone, and countless more in oil and gas fields across the country. These wells go mostly unmonitored, and rarely, if ever, checked for such leaks.
A growing list of studiesconducted over the past three years has suggested that crude oil and natural gas development, particularly in shale formations, are significant sources of methane leaks — emissions not fully included in U.S. Environmental Protection Agency greenhouse gas inventories because they are rarely monitored. Scientists say there is inadequate data available for them to know where all the leaks are and how much methane is leaking.
Methane is about 34 times as potent as a climate change-fueling greenhouse gas than carbon dioxide over a span of 100 years. Over 20 years, it’s 86 times more potent. Of all the greenhouse gases emitted by humans worldwide, methane contributes more than 40 percent of all radiative forcing, a measure of trapped heat in the atmosphere and a measuring stick of a changing climate.
Naomi Oreskes in The Nation:
Gas advocates say that while these worries might be legitimate, US greenhouse gas emissions nonetheless fell between 2008 and 2012, partly because of the way gas is replacing coal in electricity generation. This claim needs to be closely examined. In fact, it seems as if the lion’s share of that decrease was simply the result of the near global economic meltdown of 2007–08 and the Great Recession that followed. When economic activity falls, energy use falls, so emissions fall, too. Not surprisingly, preliminary data from 2013 suggest that emissions are on the rise again. Some of the rest of the 2008–12 decline was due to tighterautomobile fuel economy standards.
But how do we know what our emissions actually are? Most people would assume that we measure them, but they would be wrong. Emissions are instead calculated based on energy data—how much coal, oil and gas was bought and sold in the United States that year—multiplied by assumed rates of greenhouse gas production by those fuels. Here’s the rub: the gas calculation depends on the assumed leakage rate. If we’ve been underestimating leakage, then we’ve underestimated the emissions. Though the converse is also true, few experts think that anyone is overestimating gas leakage rates. This is not to say that emissions didn’t fall in 2008–12. They almost certainly did, again because of the recession. But the claim that there’s been a large decrease thanks to natural gas remains unproven.
Oreskes’ article is longer, packed with info,and well worth a read.