A dramatic spike in atmospheric methane over the past 16 years could be a sign that Earth’s climate could reverse within decades, scientists have warned.
Large amounts of methane from tropical wetlands in Earth’s atmosphere could trigger warming similar to ‘termination’ events that ended ice ages – replacing frosted expanses of tundra with tropical savannah, new study suggests . Researchers first detected a strange spike in methane emissions in 2006, but until now it was unclear where the gas was leaking from and whether it was a new trend.
“A termination is a major rearrangement of the Earth’s climate system,” study lead author Euan Nisbet, Emeritus Professor of Earth Sciences at Royal Holloway, University of London, told Live Science. “These repeated changes took the world from ice ages to the type of interglacial we have now.”
Ice Age endings generally occur in three phases, which are recorded in ice cores dating back 800,000 years. The initial phase is characterized by a gradual rise in methane and CO2, leading to global warming over a few thousand years. A sharp rise in temperatures follows, fueled by a puff of methane, which stabilizes in a third phase lasting several thousand years.
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“In termination, which takes thousands of years, there is this abrupt phase, which only takes a few decades,” Nisbet said. “During this abrupt phase, the methane surges and it is likely driven by tropical wetlands.”
Methane is a potent greenhouse gas emitted by both human activities – including fossil fuel burning, landfills and agriculture – and natural processes, such as decomposition in wetlands. Human emissions soared in the 1980s with the expansion of the natural gas industry and leveled off in the 1990s, Nisbet said.
But in late 2006, something “very, very strange” happened, he said. Methane began to rise again, but there was no drastic change in human activity to blame – and the researchers scratched their heads. Then, in 2013, Nisbet and his colleagues realized this increase was accelerating. In 2020, methane was rising at the fastest rate on record, he said.
“Looks like there’s a big, new source of methane igniting,” Nisbet said.
An avalanche of studies since 2019 ultimately attributed the strange spike to soaring emissions from tropical wetlands, mainly in Africa. A “significant change” in the tropical climate attributed to human-caused climate change has led to wetlands becoming larger and more plants growing there, leading to more decomposition – a process that produces methane, Nisbet said. .
In the new study, published July 14 in the journal Global biogeochemical cyclesNisbet and his colleagues compared current trends in atmospheric methane to the abrupt phase of warming at the end of the Ice Age.
“The closest analogy we have to what we think is happening today is those layoffs,” Nisbet said.
Although the evidence is inconclusive, the scale of such climate change is worth pondering, he added. In the past, the endings turned vast swathes of icy tundra in the northern hemisphere into tropical grasslands roamed by hippos, Nisbet said. There is no way of knowing what a termination might mean today, given that we are not in an ice age. “We’re not saying we have proof that this is happening, but we are raising the question.”
Regardless of whether large-scale climate change is on the horizon, tackling methane emissions should be high on our priority list, Nisbet said. “There’s a lot we can do to reduce methane,” he said, and that includes plugging gas leaks and tackling emissions from manure, landfills and crop waste.
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