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We could be 16 years into a methane-fueled 'termination' event significant enough to end an ice age

www.space.com We could be 16 years into a methane-fueled 'termination' event significant enough to end an ice age

Methane emissions from tropical wetlands have been soaring since 2006.

We could be 16 years into a methane-fueled 'termination' event significant enough to end an ice age

Laymans media

https://www.space.com/climate-change-termination-event-end-ice-age

Academic source

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GB007875

Plain Language Summary Atmospheric methane's unprecedented current growth, which in part may be driven by surging wetland emissions, has strong similarities to ice core methane records during glacial-interglacial “termination” events marking global reorganizations of the planetary climate system. Here we compare current and termination-event methane records to test the hypothesis that a termination-scale change may currently be in progress.

ABSTRACT

Atmospheric methane's rapid growth from late 2006 is unprecedented in the observational record. Assessment of atmospheric methane data attributes a large fraction of this atmospheric growth to increased natural emissions over the tropics, which appear to be responding to changes in anthropogenic climate forcing. Isotopically lighter measurements of 13Cch4 are consistent with the recent atmospheric methane growth being mainly driven by an increase in emissions from microbial sources, particularly wetlands. The global methane budget is currently in disequilibrium and new inputs are as yet poorly quantified. Although microbial emissions from agriculture and waste sources have increased between 2006 and 2022 by perhaps 35 Tg/yr, with wide uncertainty, approximately another 35–45 Tg/yr of the recent net growth in methane emissions may have been driven by natural biogenic processes, especially wetland feedbacks to climate change. A model comparison shows that recent changes may be comparable or greater in scale and speed than methane's growth and isotopic shift during past glacial/interglacial termination events. It remains possible that methane's current growth is within the range of Holocene variability, but it is also possible that methane's recent growth and isotopic shift may indicate a large-scale reorganization of the natural climate and biosphere is under way.

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19 comments

  • that delta carbon-13 curve is unsettling

    • What's delta carbon-13?

      • i'm looking at figure 3 in the academic source.

        delta carbon-13 is a measure of the ratio of carbon-12 vs. carbon-13 in a sample, in this case in samples of atmospheric methane gas. the lower the value, the fewer carbon-13 isotopes there are relative to carbon-12 isotopes. carbon-13 is stable, it doesn't radioactively decay.

        https://en.wikipedia.org/wiki/Δ13C

        so if you can date samples of atmosphere trapped in ice cores and measure the amount and isotopic composition of the methane then you can construct a graph like that figure 3. different processes result in distinct isotopic signatures for the methane released into the atmosphere. what their chart shows is that from about 1100 c.e. to 1900 c.e. the delta carbon-13 ratio dropped by about 2 per-mil while atmospheric methane concentration rose, which they attribute to a decrease in biomass burning sources of methane and an increase in agricultural sources of methane.

        then in 1900 c.e. there's a big increase in atmospheric methane along with a big increase in delta carbon-13. fossil fuel sources of methane are much heavier than natural sources, so as trapped methane was released into the atmosphere it produced a sharp change in the isotopic ratio.

        but then about 15 years ago the isotopic signature sharply reversed course even as methane concentration started suddenly rising more rapidly. so something weird is going on these past two decades where we've possibly already started feedback loops that result in releasing trapped permafrost methane, for example. the paper suggests it's mostly from tropical wetlands, but the focus of the paper is on the isotopic observations.

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