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Japan 2011 earthquake released tons of greenhouse gas

When the 2011 earthquake struck Japan, it sparked a tsunami that decimated scores of coastal villages and caused a meltdown at one of the country's nuclear facilities.

Now, a study finds that the disaster also was responsible for the release of thousands of tons of climate-warming and ozone-depleting chemicals into the atmosphere.

Writing in Geophysical Research Letters, a journal of the American Geophysical Union, researchers concluded that 6,600 metric tons (7,275 U.S. tons) of gases stored in insulation, appliances and other equipment were released into the atmosphere when thousands of buildings were damaged or destroyed by the the 9.0 magnitude earthquake and tsunami.

Emissions of these chemicals, called halocarbons, increased by 21 percent to 91 percent over typical levels, according to the study.

"What we found is a new mechanism of halocarbon emissions coming from the earthquake," said Takuya Saito, a senior researcher at the National Institute for Environmental Studies in Tsukuba, Japan, and lead author of the new paper.

The halocarbons released include chemicals that deplete the ozone layer and are responsible for rising global temperatures. These include chlorofluorocarbons like CFC-11, a powerful ozone-depleting chemical used in foam insulation until it was phased out in 1996, and hydrochlorofluorocarbons like HCFC-22, an ozone-depleting refrigerant that is also a powerful greenhouse gas and is in the process of being phased out of use. Among other halocarbons released by the earthquake were hydrofluorocarbons, or HFCs, and sulfur hexafluoride, both potent greenhouse gases.

To get a sense of the impact, the researchers said the amount of halocarbons released was equivalent to the release of 19.2 million metric tons (21.2 million U.S. tons) of carbon dioxide into the atmosphere - an amount equal to about 10 percent of Japanese vehicle emissions in 2011.

Saito and his colleagues decided to examine the role of these chemicals after air monitoring stations recorded high levels of them. The stations are located on Hateruma Island, east of Taiwan; Cape Ochiishi, on the east side of Hokkaido; and Ryori, north of Tokyo on Honshu.

The researchers then took the air station data and combined it with an atmospheric model and other mathematical methods to figure out that increased emissions from the earthquake were involved and how much of the emissions could be attributed to the disaster.

They found that emissions of all six halocarbons were higher from March 2011 to February 2012 than they were during the same period a year earlier and a year after.

The most common halocarbon, HCFC-22, was 38 percent higher after the quake while emissions of CFC-11 were 72 percent higher. HFC-134a and HFC-32 rose by 49 percent and 63 percent, respectively.

As a result, the surge of halocarbons increased Japan's contribution from those six gases to ozone loss by 38 percent from March 2011 to February 2012 and led to an increase of 36 percent in the country's contribution to heat-trapping greenhouse gas emissions.

On a global scale, these gases contributed less than a percent of ozone-depleting and greenhouse gas emissions. Part of that is due to the fact these six gases are minor contributors to global warming compared to carbon dioxide, methane or nitrous oxide.

Steve Montzka, an atmospheric scientist at the National Oceanic and Atmospheric Administration who didn't contribute to the study, said the findings "made sense" since the destruction caused by the disaster in a country as developed as Japan would have caused significant amounts of chemicals to leak into the atmosphere.

"For Japan, this event changed their emission footprint perhaps from quarter to a third," he said. "If they want their understanding of their greenhouse gas emissions to be accurate, then Japan would have to take into account these types of events. Without it, their inventory would have been inaccurate."

And while this one event didn't dramatically alter the global climate picture, Montzka said it would be wise in the future to consider just how much natural and manmade disasters contribute to emissions.

"On a global scale, this one event had a measurable impact on global emissions but it was pretty darn small. This event didn't change things much at all," he said. "But you have destructive events happening all the time and in all different places. The accumulation over time and space of these events would enhance emissions in a way inventories may not account for. But how much is not clear."

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