A new study led by Professor Mark Trimmer of Queen Mary University of London, published in the journal Nature Climate Change, explains how increases in natural methane emissions will be maximised under future climate warming.
Say 'methane' and most people think of cows, yet nearly half of all methane is produced by microbes in the natural world, especially lakes, ponds and wet soils. How much methane reaches our atmosphere depends on a balance between the production of methane by one type of microbe and the consumption of methane by another type. We know in a simple sense that these methane related microbes are stimulated by warming, but how both types will respond to warming over the next century is unknown.
The scientists used a unique natural experiment spanning the northern hemisphere to test the effect of warming on the methane balance over centuries to millennial time scales that is, after plenty of time for the microbes to adjust to climate change. They used samples collected from naturally warmed streams in remote parts of Alaska, Greenland, Iceland, Svalbard and Kamchatka (Russia). They showed that while methane consuming microbes do work harder under warmer conditions, they cannot fully check the extra methane being produced with warming. Worryingly this new study thus describes a seemingly inevitable increase in methane emissions as Earth continues to warm, building a positive feedback loop through climate change and still higher temperatures.
Scientist Dr Sarah Faye Harpenslager (now of B-Ware Research Centre and Radboud University) who led the field work to remote sites near the Arctic said "Doing fieldwork in these remote settings was both a unique and challenging experience. Luckily, we had a great multidisciplinary team of scientists, working together to collect samples and perform measurements under difficult conditions."
And Professor Gabriel Yvon-Durocher of the University of Exeter said "What is remarkable is that despite the complexity of microbial processes involved in the emission of methane from natural ecosystems, we find the same strong temperature sensitivity among the diversity of geothermally heated freshwaters across the Arctic region".
This methane research formed part of a wider project led by Professor Guy Woodward of Imperial College and Professor Alex Dumbrell of the University of Essex who said: "We have now shown how the combined effects of warming has contrasting effects on microbes that produce methane versus those that consume it - this new insight required a uniquely ambitious genes-to-ecosystems field campaign, which spanned intercontinental scales".
