Effect of Land Use Change on Climate Greater than Thought; Hazy Picture over Aerosols

Effect of Land Use Change on Climate Greater than Thought

Last year, Roger Pielke, Sr., of Colorado State University added another complicating factor to the debate over what causes rising surface temperatures when he coauthored a major study that found that land use changes may be at least as important as greenhouse gas emissions in accounting for climate change. Growing urban areas, deforestation and reforestation, agriculture and irrigation can have strong influences on regional temperatures, precipitation and large-scale atmospheric circulation.

Now, new research from Eugenia Kalnay and Ming Cai of the University of Maryland backs up Pielkes conclusions. By comparing observed surface temperatures with a reconstruction of global weather over the past 50 years, they were able to estimate the impact of land-use changes on surface warming.

They concluded that there had been an average increase of 0.27C in surface temperature per century attributable to urban and other land-use changes. This represents half the observed change in the range of daytime temperatures, and is twice as high as previous estimates based on urbanization alone. (Nature, May 29)

Hazy Picture over Aerosols

Coming hard on the heels of the findings that soot may be responsible for more atmospheric warming than was previously thought (see previous issue), a team of researchers has looked again at the question of how much the atmosphere might be cooled by the presence of sulfate aerosols.

Their research, published in the Perspectives section of Science magazine, compared the likely cooling effects of aerosols worked out from first principles with the likely effects predicted by climate models. They found a discrepancy between the two that they were unable to explain.

The authors argue that their findings suggest that anthropogenic activity will certainly lead to a strong "forcing" of the Earths climate between 2030 and 2050. However, they also admit that the discrepancy means that "the possibility that most of the warming to date is due to natural variability must be kept open." (Science, May 16)

Etc

Point / Counterpoint

"[Kyoto] is about trying to create a level playing field for big businesses throughout the world."

-- EU Environment Commissioner Margot Wallstrom, (quoted in the Independent, Mar. 19, 2002)

"Of course its about money, about rubles. They are trying to calculate how much [the Kyoto protocol] will give."

-- Wallstrom, in response to Russian reluctance to ratify the protocol, (quoted by Reuters, May 12)

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