Methane Upsurge Mystifies
Mum's the mnemonic ...
In New Zealand we’re inordinately interested in methane. We’re unique among OECD countries, with only half our greenhouse gas emissions being from carbon dioxide - principally from the burning of fuels. The other half comes mainly from methane and nitrous oxide, both of which have a large agricultural signature. The good news is that gives us another lever to meet our climate change commitments. The bad news is that it will be at the expense of the agricultural sector that we rely on for much of our wealth.
It turns out that, through no fault of our farming sector, methane has been increasing faster than expected since 2007, as demonstrated in the plots below from a recent article that appeared in the prestigious scientific journal, Nature.
The so-called ‘isotopic composition’ of the methane gives a clue about the cause of the increase. The ratio of heavier isotope of carbon (carbon 13) to the usual form (carbon 12) is smaller in methane from biogenic origins than from geological sources. The plot below shows that that ratio is declining. So it seems that the more rapid increases since 2007 are attributable to increased emissions from the biosphere, rather than from geological sources.
The big question is: why should the biosphere suddenly be emitting more methane? The fear is that it’s a dreaded positive feedback. For example, methane that’s been locked up for decades or centuries in peat permafrost bogs in the Arctic region can be released to the atmosphere as those peat bogs thaw with global warming. And that extra methane emitted just accelerates the warming. Other possibilities, such as from changing microbial production of methane in soils and wetlands (the major source), are discussed in the paper.
Whatever the biospheric source, you might be tempted conclude that that fossil fuel extraction isn’t to blame. But if that positive feedback idea holds water, you’d be wrong because it’s CO2 that caused the warming in the first place. Also, as you can see from the above plot, extraction of fossil fuels is the 2nd largest contributor to global methane. It’s to blame for nearly a quarter of the total emissions.
The total warming footprint of methane is much smaller than CO2, but its shorter atmospheric lifetime means that action taken now has a more immediate effect. Control of methane may therefore be the key to clipping the peak warming over the next decade or two. That’s why it was such a big deal the methane was specifically targeted for action in the most recent climate negotiations in Edinburgh (COP26). I’m happy to report that New Zealand has signed up to the resulting Climate Accord on controlling methane. Sadly, our big brothers ‘across the ditch’ in Australia haven’t.
A reliable source over there informs me that of the top ten methane emitters (according to the World Bank): China (1), Russia (2), India (3), Iran (8) and Australia (10) did not sign. That means that the USA (4), Brazil (5),Indonesia (6), Pakistan (7) and Mexico (9) did sign.
Why didn’t Australia sign? Well, says my friend, it was reported in the press in Australia that the Australian delegation was sponsored by Santos Energy, a definite fossil advocate. Even if the “sponsorship” is a matter of definition, the Australian pavilion at COP26 was almost obscured by the Santos advertising.
Unfortunately, says my anonymous source, “they own both major political parties”.
Sadly, it seems that it’s not only in the USA that fossil fuel interests have bought off politicians. In New Zealand there are strict rules on political donations, and any that exceed certain thresholds must be declared. The world would be a better place if all democracies adopted similar rules to ensure politicians represent the interests of their voters rather than their bankrollers.
Thanks for reading this. Previous posts on the intersection between Ozone, UV, Climate, and Health can be found at my UV & You area at Substack. Click below to share or subscribe for occasional free updates.