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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

    Control methane now, greenhouse gas expert warns

    Robert Hogwarth warns against the US pursuit of natural gas. Methane accounts for over 40% of current radiative forcing, and natural gas is the largest methane source in the US.

    Robert Howarth, greenhouse gas expert and ecology and environmental biology professor, fears that we may not be many years away from an environmental tipping point – and disaster.

    “We have to control methane immediately, and natural gas is the largest methane pollution source in the United States,” said Howarth,...

    Howarth points to “radiative forcing,” a measure of trapped heat in Earth’s atmosphere from man-made greenhouse gases. The current role of methane looms large, he says, contributing over 40 percent of current radiative forcing from all greenhouse gases,...

    If society aggressively controlled carbon dioxide emissions, but ignored methane emissions, the planet would warm to the dangerous 1.5 to 2.0 degree Celsius threshold within 15 to 35 years. [emphasis mine]

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      Ruth Anthony-Gardner

      Dr. Robert Howarth refutes the natural gas bridge-fuel myth.

      Replacing coal, oil with natural gas will not help fight global war...

      Both shale gas and conventional natural gas have a larger greenhouse gas footprint than do coal or oil, especially for the primary uses of residential and commercial heating.

      "While emissions of carbon dioxide are less from natural gas than from coal and oil, methane emissions are far greater. Methane is such a potent greenhouse gas that these emissions make natural gas a dangerous fuel from the standpoint of global warming over the next several decades," said Dr. Howarth. "Society should wean ourselves from all fossil fuels and not rely on the myth that natural gas is an acceptable bridge fuel to a sustainable future."

      image source

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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