Pollution's Surprise Consequence: A Slowdown in Global Warming


Which do you want first: the good news caused by bad news, or the straightforward bad news?

Let’s start with the kinda good news, which is that Reuters reported recently that many climate scientists have acknowledged an “apparent slowdown” in global warming since 2000. This is a reversal of the fast warming they observed in the 1990s. But the scientists went on to note that, “the long-term trend is up. So far, 2012 is the eighth warmest year in records back to the mid-19th century, according to U.S. data.”

However, that latter bit of information is not the bad news. For that we need to look to China. Myles Allen, a professor of Geosystem Science at Oxford University, told Reuters that, "The simplest explanation is that China's sulphate emissions did not go down as they suggested they would,” and he indicated that rising pollution in many emerging nations was also a factor.

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When Allen was contacted by TakePart he explained that he was referring to the fine aerosols that are generated by sulphur pollution, mostly from coal-fired power plants. “Although China is doing a lot better than it has in the past on cleaning up smokestacks, the general consensus seems to be that earlier projections of how fast it would clean them up were over-optimistic,” he said.

“So the massive increase in coal-fired power in China over the past decade may have had some cooling impact on climate,” Allen said. The reason is that the sulphate that’s expelled by coal-fired power plants dims sunlight and thus offsets warming. Allen adds that, “The downturn in power output of the sun is probably also a contributor, and trends in stratospheric water vapor have also been suggested.”

But a decade’s worth of data may not be enough to draw conclusions regarding any long-term trends. “It has long been acknowledged, for example by the IPCC, [Intergovernmental Panel on Climate Change] that a decade is too short a time to observe climate trends because there is so much variability in climate on this timescale,” said Allen. 

He referenced an article he and his colleagues published in Nature in 1994 where, “We estimated about 15 years as the minimum we should expect to detect a trend, and even then, there is a chance that any given 15-year period will be exceptional. I was involved in the 2001 IPCC report, and we made a point of not over-interpreting the apparent acceleration of warming from the 1980s through the 1990s, for precisely this reason. So it also doesn't make sense to over-interpret the apparent deceleration from the 1990s through the 2000s. The simplest explanation seems to me to be that we just had a run of exceptionally warm years around the millennium, and the system is now reverting to trend.”

On the other hand, some scientists simply believe that natural variations are the main cause of rising temperatures, not the emissions caused by human activity. And that’s not a trend that’s expected to reverse itself any time soon.

Are you surprised to learn that industrial pollution can slow the rise in global temperatures?

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Lawrence Karol is a writer and editor who lives with his dog, Mike. He is a former Gourmet staffer and enjoys writing about design, food, travel and lots of other stuff. @WriteEditDream | Email Lawrence | TakePart.com