The oil and gas industry has had a far worse impact on the climate than previously believed, according to a study indicating that human emissions of fossil methane have been underestimated by up to 40%.
Although the research will add to pressure on fossil fuel companies, scientists said there was cause for hope because it showed a big extra benefit could come from tighter regulation of the industry and a faster shift towards renewable energy.
Methane has a greenhouse effect that is about 80 times more potent than carbon dioxide over a 20-year period and is responsible for at least 25% of global heating, according to the UN Environment Programme.
In the past two centuries, the amount of methane in the atmosphere has more than doubled, though there has long been uncertainty about whether the source was biological – from agriculture, livestock or landfills – or from fossil fuels. There were also doubts about what share of fossil methane was naturally released and what share was from industry.
Earlier estimates were based on intermittent, bottom-up monitoring of oil and gas companies and comparisons with geological evidence from the end of the Pleistocene epoch, about 11,600 years ago.
For a more accurate comparison, a team at the University of Rochester in the US examined levels of methane in the pre-industrial era about 300 years ago. This was achieved by analysing air from that period trapped in glaciers in Greenland. The sample – made up of about a tonne of ice – was extracted with a Blue Ice Drill, capable of producing the world’s biggest ice cores.
The findings, published in Nature, suggest the share of naturally released fossil methane has been overestimated by “an order of magnitude”, which means that human activities are 25-40% more responsible for fossil methane in the atmosphere than thought.
This strengthens suspicions that fossil fuel companies are not fully accounting for their impact on the climate, particularly with regard to methane – a colourless, odourless gas that many plants routinely vent into the atmosphere.
An earlier study revealed methane emissions from US oil and gas plants were 60% higher than reported to the Environmental Protection Agency.