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Methane, more scary than we thought

Methane’s Contribution to Global Warming Is Worse than You Thought

It seems we've been "fudging the numbers" in a sense, when comparing the global warming potential of methane to CO2. When global warming potential (GWP) of a gas is calculated, a time frame is assumed. The IPCC decided to use a 100 year time frame.

With a 100 year time frame methane heats up the planet 21 times as much as CO2. The problem with that assumption is that we don't have 100 years. A 20 year time frame would be much more realistic, given the urgency of climate crisis. With a 20 year time frame...

... any CH4 released today is at least 56 times more heat-trapping than a molecule of C02 also released today. And because of the way it reacts in the atmosphere, the number is probably even higher, according to research conducted by  Drew Shindell , a scientist at NASA’s Goddard Space Center. [emphasis mine]

 

What if we were to use the IPCC’s 20-year comparison instead of its 100-year comparison? For starters, it would force us to get much more serious about tackling  the sources of methane emissions. Here in the US, the top methane sources are the decomposition of wastes in landfills, agriculture (from ruminant digestion), and leaks from natural gas drilling and transmission. A new emphasis on methane would require us to get smarter about capturing methane at landfills, reduce the market incentives that encourage Americans’ meat-heavy diets, and ensure that methane isn’t leaking from fracking operations.

But beyond the policy specifics, adopting the 20-year global warming potential comparisons would be useful for changing how we think about climate change.

And we appear to be approaching some irrevocable tipping points that will create powerful negative feedback loops, the most worrisome being  the release of methane  stores at the bottom of the ocean and locked into sub-Arctic permafrost.

Image from Arctic Methane Release Tipping Point Diagram
With 56 times as much warming as CO2 in mind, we'd take this feedback more seriously.

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  • up

    Ruth Anthony-Gardner

    A new study suggests that oceans warming from CO2 absorption could trigger a second - far worse - warming event two thousand years later, that lasts 200,ooo years.

    Ancient Earth Warmed Dramatically After a One-Two Carbon Punch

    ... the authors argue that a release of methane from deposits below the seafloor would explain both the rate of change and the curious double pulses. This methane is normally safely locked away in a solid form called methane clathrate, but even an undersea landslide might have been enough to destabilize an area of the seafloor and unlock a vast clathrate deposit. That kind of event could have triggered the short-lived pulse of global warming before the main PETM event.

    In response to this initial pulse, Earth’s oceans might have soaked up the excess atmospheric heat. If they did, though, it’s possible that this natural recovery mechanism triggered the main event. Warmer oceans can themselves destabilize clathrate deposits, which might explain where the second carbon pulse came from, says Wing. If this scenario is correct, it makes the PETM even more relevant to today—the oceans are warming up once more, and clathrate deposits below the seafloor are again beginning to destabilize. [emphasis mine]

    • up

      Ruth Anthony-Gardner

      Methane is leaking from permafrost offshore Siberia

      New research indicates that permafrost in the West Yamal shelf is already leaking profoundly, and explosive methane gas hydrate release will likely occur when the water warms 2 degrees.

      Portnov and his colleagues have recently published two papers about permafrost offshore West Yamal, in the Kara Sea.

      When the ice age ended some 12 000 years ago, and the climate warmed up, the ocean levels increased. Permafrost was submerged under the ocean water, and started it´s slow thawing. One of the reasons it has not thawed completely so far, is that bottom water temperatures are low, some - 0,5 degrees .

      It was previously proposed that the permafrost in the Kara Sea, and other Arctic areas, extends to water depths up to 100 meters, creating a seal that gas cannot bypass. Portnov and collegues have found that the West Yamal shelf is leaking, profoundly, at depths much shallower than that.

      Significant amount of gas is leaking at depths between 20 and 50 meters. This suggests that a continuous permafrost seal is much smaller than proposed. Close to the shore the permafrost seal may be few hundred meters thick, but tapers off towards 20 meters water depth. And it is fragile.

      "If the temperature of the oceans increases by two degrees as suggested by some reports, it will accelerate the thawing to the extreme. A warming climate could lead to an explosive gas release from the shallow areas."

      Permafrost keeps the free methane gas in the sediments. But it also stabilizes gas hydrates,...

      Gas hydrates contain huge amount of methane gas, and it is destabilization of these that is believed to have caused the craters on the Yamal Peninsula. [emphasis mine]

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        Ruth Anthony-Gardner

        Strong currents facilitate methane's escape from Arctic seas.

        "We found that strong, fluctuating, currents were common above methane seeps, meaning that methane-consuming bacteria may not be as effective for regulating emissions of methane to the atmosphere as previously thought,"... [emphasis mine]

        Strong currents promote release of Arctic greenhouse gas