Scientific American’s global climate change issue (9/06) outlined a painful and politically almost inconceivable approach to keeping terrestrial climate within the bounds of human evolutionary history.
Alas, each bit of research on climate change seems to worsen the picture. The latest article on methane release is typical (note my emphasis, below):
BBC NEWS | Science/Nature | Methane bubbles climate trouble
… Scientists from Russia and the US measured methane bubbling from a number of thawing lakes.
Writing in the journal Nature, they suggest the methane release is hastened by warmer temperatures, positively feeding back into global warming.
… "Thaw lakes in north Siberia are known to emit methane, but the magnitude of these emissions remains uncertain," the scientists write.
"We show that methane flux from thaw lakes in our study region may be five times greater than previously estimated."
… The study depended on the systematic deployment of bubble traps on two lakes in the Cherskii region of Siberia, supplemented by ground-based and aerial observations of a further 95 lakes.
Katey Walker from the University of Alaska at Fairbanks and her colleagues calculate that across the region, thaw lakes lakes emit 3.8 teragrams (Tg, million million grams) per year.
The contribution of these lakes is small compared to the IPCC estimate of total global methane production, 600 Tg per year.
More than half of this total comes from human activities, notably farming.
The importance of the Siberian release may lie in the relationship between warming and methane production.
If a high release rate of a greenhouse gas is being triggered by rising temperatures, that will in turn stimulate still higher temperatures - a positive feedback mechanism…
These particular lakes produce about 1/150th of global methane, or 1/75th of what humans (esp. farmers — is that cow gas?) produce. So what’s the impact? This BBC news article is missing some context. This 1995 journal article helps:
… the total annual global source strength of atmospheric methane, an important greenhouse gas, is estimated to be 500 teragrams, with anthropogenic sources accounting for 340 teragrams. With an estimated sink strength of 460 teragrams per year, the annual increase of atmospheric methane is 40 teragrams.
So if 40 is the right denominator here, then this region alone is causing a 5–10% increase in net methane growth (we’ve apparently gone from 500 to 600 TG/year output in 10 years, but I assume agricultural sinks have also grown, so I can’t guess the actual net increase). Siberia is not the entire world of permafrost, so, bottom line, this probably does represent a significant increase in net atmospheric methane accumulation. It’s just hard to see that from the BBC article.
The feasibility of the almost unattainable ‘conservative’ path to climate restraint seems to have shrunk considerably. When the climate models are updated with the new data, it seems possible that we’ll need both the ‘conservative’ approaches and some new, fairly radical, technologies as well.
I can’t imagine the world my children will inherit …
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