Tuesday, 5 July 2011

The China conundrum - two eco-wrongs don't make a right


China seems to have developed something of a split personality overnight, in the global warming stakes. After a decade of being painted as the villain of the piece, with many wagging their fingers disapprovingly at China's multiplying smokestacks, a paper published overnight has turned things on their head. It seems that China's noxious emissions have actually been helping to cool the climate, if the tabloid interpretation of the study, published online by the PNAS, is to be believed.

If CO2 emissions are the bad boy of climate change, then SO2 is the newly painted hero, helping to vanquish the seemingly irrepressible warming, that carbon dioxide has trailed in its wake. The paper has tied the recent slowing down of global warming, over the decade since 1998, to a burst of sulfate emissions from China's coal-burning power stations.

Of course, the idea that global warming has left the scene over the last decade is something hotly debated. Cherry-picking years on the wildly wiggling graph of global temperatures can easily 'prove' that global warming is 'absent' at any time in the last 40 years– conveniently forgetting that it is the long term average that matters. Yearly changes are the rule, and invariably larger than the 'drip-drip' feed of a warming climate, due to greenhouse gases.

But on most measures of global temperature, averaged over 10 or 15 years, the decade since 1998's El Nino has certainly shown a slower rate of warming – still warming, just not as fast. So asking why that might be the case is an important line of inquiry to follow. And the answer gleaned by this research team is that the rise in the China's dirty-coal burning, from 2000 onwards, has helped partially mask the warming from CO2.

Sulfate particles from coal combustion cause a hazy smoke around power plants – and that haze helps to reflect sunlight back into out into space. So more sulfate emissions means more cooling. This isn't the first time that something such as this has happened. The period from 1940 to 1970 saw massively rising sulfate pollution, which rose three-fold over that period. And global temperatures were definitely affected – with an general flat-lining of global temperatures over that period.

But sulfates particles don't hang around in the atmosphere. They get washed out – literally – falling as increasingly acidic rain. It was the deafening-hush of forests, stripped of life by acid rain, that led to action to remove sulfates from smokestack fumes, across the industrialized world, in the 1970s. It worked, but that also heralded the start of three decades of faster rising temperatures across the globe.

Now that respected researchers are again making a link between increased SO2 and global cooling, you can almost here the mental cogs turning amongst certain 'business-as-usual' opinion-makers. Maybe we shouldn't be scrubbing out all those nasties from smoky Chinese coal-powered stations. Perhaps we should be paying the Chinese to keep pumping out their sulfates, and 'cancel' global warming for ever.

The problem is that the global ecosystem isn't a single-issue problem. We are assailing Planet Earth on many front simultaneously, producing effects that both reinforce, and cancel, in ways that will always be poorly understood. The real lesson is that we need less of both CO2 and SO2, and all the other pollutants that our society so blithely foists on the natural world. We can only right these wrongs by learning to live within the limits of the planet that sustains us; not by wildly pressing levers in the hope we can 'fix the machine'.

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