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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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    Ruth Anthony-Gardner

    Mantle Methane? Who knew! Here's a Reddit discussion clarifying another source of Arctic methane hydrates.

    NTE means "near term extinction". This discussion was in response to the recently discovered methane megaflare in the Laptev Sea. (summary here) (definition of "obduction")

    BR: If the the tipping point to NTE appears to revolve around the release of methane, how much methane is there?

    M: A lot. There appears to be a minimum of one and two times more methane than all of the fossil fuel carbon in sequestered the Earth's mantel.[1]

    BR: How can that be? I mean if fossil fuel came from biomass, then where did all of the methane come from?

    M: Mantle methane seems to be formed from the reduction of oceanic carbonates by water in the presence of iron oxides buried to depths of 100 km to 300 km in the Asthenosphere and at temperatures above 1200°C. This, of course, is a vast, non-organic or geologic methane, formed near the earth's mantel under a massive pressure and has been there for millennia. Thus, methane hydrates can be found all around the Earth, even off the continental shelf of the Gulf of Mexico.

    But the Arctic is a focal point for the collision of tectonic plate subduction and obduction. Plate migration creates methane routes through new fractures in the earth's mantel, but the fractures have been sealed over by Arctic ice. For the first time in human history, the ice-sealed fractures are thawing. Methane is rising through the fractures and into the atmo­sphere.[2][3]

    BR: If this were true, why has it not happen before?

    M: It most likely has happened in the distant past. Approximately 65 million years ago the Earth went through a similar heating process. Of course, there were no humans at that time, so the most plausible explanation is the release of geologic methane.

    discussion page

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      Ruth Anthony-Gardner

      Last year extra methane came out of the Arctic from October to March, as a result of warm water incursions. It takes months for the warm water from the Pacific and Atlantic Oceans to arrive deep in the Arctic Ocean. This image shows that the 2014 warm water anomalies from the Bering Strait (on the left) and the Atlantic (on the right) are larger than last year.

      Last year, methane emissions started to become huge in October and this lasted for some six months.

      This year, there is even more ocean heat present, especially in the north Atlantic and the north Pacific. On September 29, 2014, methane levels as high as 2641 parts per billion were recorded and it looks like worse is yet to come.

      Warm water extends from Laptev Sea to North Pole

      • 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]