Global emissions of the potent greenhouse gas methane hit an all-time high in 2017, according to a pair of new studies released this week by researchers with the Global Carbon Project. Agriculture, landfill waste and fossil fuel production are driving the sharp increase in methane emissions from human activities, reports Maria Temming of Science News.
Though worldwide data is only available through 2017, the researchers behind the studies say the planet’s soaring methane emissions have “almost certainly” continued to rise despite this year’s temporary coronavirus-related reductions in global emissions, reports Hiroko Tabuchi of the New York Times.
“The atmosphere does not suggest that anything has slowed down for methane emissions in the last two years,” Rob Jackson, an environmental scientist at Stanford University and co-author of both studies, tells Science News. “If anything, it’s possibly speeding up.”
Per Science News, the concentration of methane in Earth’s atmosphere increased from 1,857 parts per billion in 2017 to 1,875 parts per billion in 2019, according to NOAA.
The research’s findings, published July 14 in the journals Earth System Science Data and Environmental Research Letters, place Earth on a path for the most catastrophic warming scenario outlined by climate models, reports Denise Chow for NBC News.
Annual emissions of methane have gone up by nine percent since the early 2000s—that amounts 50 million more tons every year— and the methane that has been pumped into the atmosphere since 2000 is equivalent to adding 350 million cars to the world’s roads, says Jackson in a statement. If left unchecked, the emissions scenario the world is currently tracking is predicted to warm the planet by three to four degrees Celsius by 2100, according to the statement.
This increase would blow past the goals of limiting global warming to 2 degrees, let alone the more ambitious goal of 1.5 degrees, set by world leaders at the 2015 Paris climate agreement. Exceeding these thresholds is predicted to entail a litany of ills for tens of millions of people across the world, including increasingly common life-threatening heatwaves, freshwater shortages and coastal flooding due to rising sea levels, according to the Times.
Methane is “arguably the second most important” greenhouse gas behind carbon dioxide, atmospheric scientist Alexander Turner, who will soon be based at the University of Washington and wasn’t involved in the new research, tells Science News. That’s because methane can trap roughly 28 times more heat than carbon dioxide over a 100-year period, reports Jack Guy for CNN.
Jackson tells the Times that the danger posed by methane emissions is likely to grow in coming years unless serious action is taken.
“There’s a hint that we might be able to reach peak carbon dioxide emissions very soon. But we don’t appear to be even close to peak methane,” Jackson tells the Times. “It isn’t going down in agriculture, it isn’t going down with fossil fuel use.”
Human activities were responsible for more than half of the methane emissions seen from 2000 to 2017, according to the research. Overall, agriculture contributed two-thirds of humanity’s share of emissions of the colorless gas while fossil fuels were responsible for most of the remaining third. Emissions of methane from agriculture and fossil fuels rose nearly 11 and 15 percent, respectively, compared to their 2000 to 2006 averages, driving the overall increase in global emissions. Natural sources of methane include wetlands, but these sources showed little increase over the study period despite greater scientific uncertainty as to their relative contributions.
Agricultural emissions come primarily from livestock such as cattle and sheep, which burp methane as a result of how they digest their food. In the fossil fuel sector, methane is released by coal mining and leaks from oil and gas wells, pipelines as well as gas stoves in peoples’ homes.
The increases in emissions were sharpest in Africa and the Middle East; China; and South Asia and Oceania, which had each added 10 to 15 million tons of methane emissions per year by 2017, according to the report. China’s increasing methane emissions were largely due to an uptick in coal use, per the Times, while agriculture drove the rise in South Asia and Oceania as well as, to a lesser extent, Africa, according to Science News.
In the United States, the booming natural gas industry was responsible for 4.5 million tons of methane emissions, according to the statement.
Making meaningful reductions in methane emissions would require countries to reduce their reliance on fossil fuels, the researchers say in the statement. Less holistic solutions to the emissions from the fossil fuel industry include plugging leaks in oil and gas pipelines and wells.
Innovations in the agricultural sector to reduce the methane released by livestock and rice paddies could also have climate benefits, according to the researchers.
“The key message is that methane concentrations and emissions are still rising, and we know the main cause,” Marielle Saunois, an environmental scientist at the Laboratory for Climate and Environmental Sciences in France and co-author of both studies, tells the Times. “This is not the right path.”