Chinese sulphur pollution dampens/disguises global warming over last decade

A strange publication with an interesting conclusion.

It is strange because we can witness ‘skeptic’-style temperature graph cherry picking by (two economists and) two actual climate scientists of Boston University (Robert Kaufmann and Michael Mann).

In their their PNAS publication they start off by incorrectly stating the Earth hasn’t warmed over the decade since 1998. So we have to start with denying just that.

‘From summer to winter the climate cools’

First of all 1998 was an El Niño peak, so not representing the trend mean of that time. [Besides the Hadley Centre record may have inflated the 1998 measurements - by overrepresenting lower lattitudes. The El Niño peak was probably not as high as often shown in graphs that include the Hadley record. We prefer NASA GISS as best-balanced.]

Secondly, we know the real trend says warming.

Thirdly, if indeed you want to go the cherry orchard route, 2005 and 2007 were already hotter than 1998 [as were 2009 and 2010 – although these years are indeed officially more than a decade away – they do of course show were the trend is going]. The last year of the pseudo decade, 2008, was indeed a La Niña year, as the researchers state themselves – and was indeed cooler than 1998.

Right. Hopefully that misunderstanding is out of the way.

Not as fast as CO2 rise

We can however confirm the temperature graph does not seem to fully correspond with the rising CO2 concentrations, as both CO2 emissions keep breaking records and the rise of the atmospheric CO2 level seems to be accelerating over recent years.

So, somehow, over these last few years the world hasn’t warmed as much as ‘it should have’. And for this the researchers have an explanation – and a funny way of expressing that: the drop from El Niño to La Niña, together with declining solar insulation caused the cooling, because “rapid growth in short-lived sulphur emissions partially offsets rising greenhouse gas concentrations” – thus creating a smaller net anthropogenic climate forcing.

Sulphur aerosols

Sulphur aerosols can remain airborn for months to several years, during which time they lower the average albedo and thus reflect sunlight back to the cosmos.

The increased sulphur emissions are linked to a 100 percent increase in coal consumption over the period 1998-2008 in China. As the Chinese industry and power sector is gradually being modernised, with the aim to increase efficiency and alleviate local air pollution, much less sulphur will remain in the air – and the albedo will decrease again, allowing global temperatures to quickly catch up on the actual CO2 concentrations.

‘Coal geoengineering’

The research does seem to confirm the cooling potential of sulphur aerosols and associated forms of SRM geoengineering. We now wonder if David Keith did not forget to include Chinese coal in his cost analyses. It may well be his cheapest option.*

[*) Science forces us to be serious here. Coal could never ‘create cooling’. That is because the sulphur is here for a couple of years at max, while the co-emitted CO2 is here for... well, forever. Emitting sulphur we are just reshaping the temperature graph, creating another dangerous thermic delay, simply buying time to set the stage for a damaging rebound.]

© Rolf Schuttenhelm | www.bitsofscience.org

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