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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Replies to This Discussion

Spikes in methane, similar to the recent one, have happened before, Michael Mann reassures us. I'm still not happy about it though.

Seen up close.

image source

Context provided by Michael Mann:

image source

The 2019 measurements are consistent with the trend over the past decade. Outliers (i.e. isolated data points that lie well above the average) are seen throughout the record. Do not over-interpret them.

Michael Mann twitter thread

Yeah, it's probably from fracking rather than methane hydrate outgassing or permafrost melting. Not a sign of having crossed a tipping point. But it's still a potent greenhouse gas.

Two aquatic plants in arctic tundra wetlands are major methane emitters in the growing season. Here's another recently discovered positive feedback of climate destabilization.

Rising plant‐mediated methane emissions from arctic wetlands

... Carex aquatilis and Arctophila fulva ...   account for two‐thirds of the total regional CH4 flux of the Barrow Peninsula. 




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