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Have Chinese Coal Plants Been Keeping Global Warming in Check?

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Chinese coal consumption doubled between 2003 and 2007, emitting large amounts of sulfur compounds that reflect some sunlight back into space, counteracting the warming effect from rising amounts of greenhouse gases. Credit: Frederic Brown/AFP/Getty Images.

Some popular myths about climate change are like zombies. You can stab them, shoot them, beat them about the head with a baseball bat, and they just get up and keep going. One such undead notion is the idea that if humans are the cause of global warming, temperatures should be going steadily upward. Any significant slowdown in the temperature increase, the argument goes, and the whole theory collapses.

That’s nonsense, according to most climate scientists. The climate system has all sorts of moving parts — ocean currents, wind patterns, changes in vegetation and ice cover and dust particles in the air. Heat moves around in complicated ways. Global warming theory predicts an overall temperature rise over decades, but slowdowns, and even brief periods of cooling are not only possible; they’re inevitable. (So, for that matter, are periods of faster-than-average warming).

The decade that just ended is a case in point. While it was the warmest ten years on record, temperatures didn’t rise as fast during the 2000’s as they did for the previous 30 years or so. And while they aren’t at all surprised by this, scientists are still trying to figure out why it happened. "The fact is that we can't account for the lack of warming at the moment,” wrote Kevin Trenberth of the National Center for Atmospheric Research in one of the “Climategate” emails, “and it is a travesty that we can't.” (This quote was widely taken out of context to suggest — falsely — that he was expressing doubt in the underlying theory that human emissions of greenhouse gases, such as carbon dioxide (CO2), are helping to warm the planet.)

Trenberth himself has suggested that the slowdown in the 2000’s happened because excess heat was being stored temporarily in the deep ocean. But a new paper published in Proceedings of the National Academy of Sciences offers a different explanation. The cause, argues lead author Robert K. Kaufmann, of Boston University’s Center for Energy and Environmental Studies, is another type of pollution — specifically, sulfur emissions from Chinese power plants. “Chinese coal consumption,” he points out, “has doubled in just four years, and they were using plenty to begin with.”

Graph of surface temperature departures from average since 1880, from four different data sources. Note the overall increase in temperatures, despite the shorter periods with level temperatures or slight cooling. Credit: Climate Central and NASA.

If unchecked by pollution controls, the sulfur creates atmospheric particles that reflect some sunlight back into space, counteracting the warming effect from rising amounts of CO2. “The short story,” says Kaufmann, “is that all of a sudden the human effects on climate cancel out during this period.”

It wouldn’t be the first time this has happened. During the middle of the 20th century, the planet went into a slight cooling phase that lasted for about 30 years. The cause: a rise in sulfate particles as the world’s economy boomed after World War II. Anti-pollution measures that went into effect starting in the 1970’s cleaned up the air — and warming started to take off again. Now, Kaufmann points out, China is beginning to deal with its own polluted air by installing scrubbers on the smokestacks of coal-fired power plants, in part because sulfur emissions are contributing to acid rain. 

Without sulfate particles to counter the effects of CO2, says Kaufmann, “there could be a big increase in warming — and we’ve already seen that happening in 2009 and 2010. The hiatus is over.”

Nobody's saying the Chinese should stop cleaning up their smokestacks, of course. Even if reflected sunlight is an unintended benefit of pollution, the harm from acid rain and other noxious substances is enormous. And while some proponents of "geoengineering" have suggested lofting sulfur compounds into the atmosphere on purpose to block the sun, the unintended consequences of such a step could be disastrous.

But not everyone accepts Kaufmann's analysis in the first place. 

It all sounds logical, and, says Hiram Levy, a climate modeler at NOAA’s Geophysical Fluid Dynamics Laboratory near Princeton, NJ, “the idea is physically sound.” But he’s not convinced that this is what’s really happening. Coal use is indeed growing in China, but it’s decreasing in other parts of the world. Globally, he estimates an overall increase of 10 percent in sulfate emissions over the last decade, which wouldn’t be enough to explain the slowdown. “At the same time,” he says, “there’s been a 10 percent increase in black carbon [emissions]” — soot, essentially, which tends to absorb sunlight and warm the air.

“If climate change were driven only by radiative forcing,” says Levy, referring to changes in how much energy arrives on Earth from the Sun, and how much escapes back to space, “I would expect all of those [temperatures] to be leveling off.” But changes over a period as short as a decade, he says, “can also involve ocean stuff.”

Kevin Trenberth is equally unimpressed. “Ninety percent of the energy imbalance ends up in the ocean,” he wrote in an email, “and so it is the SSTs [sea-surface temperatures] and upper ocean heat content that matter for surface temperatures. The model they have does not appear to consider any of this and is not physically correct.”

Even worse from, Trenberth’s perspective, is the fact that the new paper cites the period from 1998 to 2008 as the span over which temperatures were relatively flat. But as climate scientists have explained ad nauseam, 1998 was an unusually warm year, thanks to a strong El Niño event in the Pacific. Choosing 1998 as a starting point (as many climate skeptics do) inevitably makes any temperature increase that follows look artificially small.  

Trenberth, Levy and Kaufmann all agree, however — as do virtually all climate scientists — that slowdowns in global warming, some lasting as long as a decade or more, are not just expected, but inevitable as manmade greenhouse-gas emissions heat the planet. They further agree that these can come from natural effects as well as artificial ones like sulfur emissions from coal-fired power plants.

The fact that they disagree about what went on in the 2000’s doesn’t take away even a little from this underlying agreement, nor does it detract from the consensus view that manmade emissions of greenhouse gases are causing global temperatures to increase over the longer-term. 

Comments

By NikFromNYC
on July 6th, 2011

The LA Times featured cold fusion in ‘89 before its debunking. Greens were aghast!
“It’s like giving a machine gun to an idiot child.” ”“ Paul Ehrlich (mentor of John Cook of the SkepticalScience blog, author of “Climate Change Denial”)
“Clean-burning, non-polluting, hydrogen-using bulldozers still could knock down trees or build housing developments on farmland.” ”“ Paul Ciotti (LA Times)
“It gives some people the false hope that there are no limits to growth and no environmental price to be paid by having unlimited sources of energy.” ”“ Jeremy Rifkin (NY Times)
“Many people assume that cheaper, more abundant energy will mean that mankind is better off, but there is no evidence for that.” ”“ Laura Nader (sister of Ralph)

CLIMATEGATE 101: “For your eyes only…Don’t leave stuff lying around on ftp sites - you never know who is trawling them. The two MMs have been after the CRU station data for years. If they ever hear there is a Freedom of Information Act now in the UK, I think I’ll delete the file rather than send to anyone….Tom Wigley has sent me a worried email when he heard about it - thought people could ask him for his model code. He has retired officially from UEA so he can hide behind that.” - Phil “Hide The Decline” Jones to Michael “Hockey Stick” Mann

Here I present A Global Warming Digest:
Denial: http://i.min.us/ibyADs.jpg
Oceans: http://k.min.us/idAw6Y.gif
NASA: http://i.min.us/idFxzI.jpg
Thermometers: http://i.min.us/idAOoE.gif
Earth: http://k.min.us/ibtB8G.gif
Ice: http://k.min.us/ibBgw2.jpg
Authority: http://k.min.us/iby6xe.gif
Prophecy: http://i.min.us/idEHdo.jpg
Psychopathy: http://i.min.us/ibubmk.jpg
Icon: http://www.youtube.com/watch?v=tmPzLzj-3XY
Thinker: http://www.youtube.com/watch?v=n92YenWfz0Y

-=NikFromNYC=- Ph.D. in Carbon Chemistry (Columbia/Harvard)

Reply to this comment

By Charlie Petit (94708)
on July 6th, 2011

Excellent job Mike. The zombies are good, the polite demurral on the paper’s thesis, from the right experts, is even better. Personally, I just look at the graphed rise in temps, whether from the Met or NOAA or GISS, in recent decades and notice the unmistakeable smoothed trend, and the several episodes of interruption of that trend in the detailed data. They look pretty much like the one of the last ten years. What would be strange, as your sources and your story suggest, would be a metronomic rise year by relentless year.

Reply to this comment

By Sphaerica (Bob)
on July 18th, 2011

NikFromNYC,

Nice litany of tired, lame denial arguments, including every denier trick in the book, from an appeal to vacuous authority (aging jet-jockey astronauts, really?) to cherry picking (temperatures in Central England, really?) to conflating two separate and distinct ice anomalies, and more.

Really, there’s a lot of info out there.  I suggest you (or anyone who thinks you made any valid points with your posts) visit skepticalscience.com and get yourself up to speed on the truth, instead of reciting the tired, bogus stuff you’ve so eagerly bought into.

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