Climate change fight is struggling with methane
Atmospheric methane concentrations are rising faster than any time in the last two decades and are reaching the most greenhouse-gas-intensive scenarios, shows a study published in Environmental Research Letters. This surge imperils climate goals as methane emissions causes short-term warming even if its effects fade more quickly than carbon dioxide.
According to the report, methane concentrations were rising only at about 0.5 parts per billion in the early 2000’s. But in 2014 they spiked by 12.5 parts per billion and 9.9 parts per billion in 2015.
Instead, for the last three years carbon dioxide emissions have been flat. Even if the gas has continued to accumulate in the atmosphere, emissions haven’t gone up so at least in the next decade or so a higher fraction of global warming we will be seeing will be result of methane.
“Methane in the atmosphere was almost flat from about 2000 through 2006. Beginning 2007, it started upward, but in the last two years, it spiked,” said Rob Jackson, one of the study’s co-authors.
“Looking at the scenarios for future emissions, methane is starting to approach the most greenhouse gas-intensive scenarios,” Jackson said. “That’s bad news. We’re going in the wrong direction.”
The methane reaching the atmosphere comes from various human and natural sources. In fact, 60% of methane originates from human activities. Also it is the main component of natural gas, emerges from biological processes including the flooding of rice paddies and “enteric fermentation” in the stomachs of ruminant animals and is released by wetlands.
"Additional attention is urgently needed to quantify and reduce methane emissions," reads the study. Keeping global warming below two degrees Celsius (3.6 degrees Fahrenheit) is already a challenging target," said the authors referring to the Paris Agreement.
"Such a target will become increasingly difficult if reductions in methane emissions are not also addressed strongly and rapidly."
According to the 2016 Global Methane Budget in South America wetlands are the largest source of methane, followed by agriculture and waste. Overall between 2003 and 2012 the largest methane emissions came from tropical South America, Southeast Asia and China, representing 50% of global emissions.
Referring to the sudden increase, when speaking to the Washington Post Jackson said, “We think agriculture is the number one contributor to the increase. There’s been a secondary increase from fossil fuel use, partly because there continues to be more fossil fuels extracted.” But, he continued, “we don’t see evidence for a huge spike in fossil fuel emissions over temperate systems. We do think they’ve increased, but we don’t see evidence for leaky oil and gas wells causing this spike in global methane.”
As additional methane will cause the Earth to warm up faster in the coming decades, methane mitigation also offers rapid climate benefits and economic, health and agricultural co-benefits that are highly complementary to CO2 mitigation.