Global methane levels have hit an all-time high after what appears to be a near-record yearly atmospheric increase in the potent greenhouse gas.

The concentration of methane in the Earth’s atmosphere reached nearly 1,875 parts per billion in 2019, up from the previous year’s 1,866 parts per billion, according to preliminary data collected by the National Oceanic and Atmospheric Administration (NOAA).

If confirmed later this year, it would be the second highest increase in methane levels in more than two decades. The NOAA began collecting global methane data in 1983.

Though methane remains in the atmosphere for only a few years, it is 28 times more powerful than carbon dioxide at trapping the sun’s heat, and it poses an increasingly grave threat to efforts to tackle escalating global heating.

“Here we are. It’s 2020, and it’s not only not dropping. It’s not level. In fact, it’s one of the fastest growth rates we’ve seen in the last 20 years,” Drew Shindell, a climate scientist at Duke University, told Scientific American.

Scientists last year warned higher methane levels will make it even harder to reach targets set by the Paris climate change agreement.

Though uncertain about the source of the year-on-year increases, NOAA researchers have previously said much of it was coming from the tropics.

They believe it is likely due to microbial changes in methane-belching tropical wetlands, potentially caused by warmer temperatures in what amounts to a dangerous feedback loop.

The hypothesis is that as the climate warms the efficiency of the microbial communities that convert organic matter into methane increases.

But Rob Jackson, professor of Earth system science at Stanford University, said some of last year’s surge was likely also due to increases from agriculture and natural gas use.

In its annual sustainability report released last week, the fossil fuel company Shell revealed its annual methane emissions stood at 91,000 tonnes, down from 92,000 a year earlier.

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