Science Looks At Cooling Particles, Effect On Warming Estimates

Vivi Gorman
Posted on Monday 13th July 2009

Greenhouse gases are emitted every day in the daily generation of power used to power our economy, businesses, buildings and homes. These gases are considered by many scientists to cause climate warming. However, airborne pollution also includes particulates, and scientists are now saying that while some particulates add to warming, others have a cooling effect.

According to a Science Daily article published July 9, black carbon has a warming effect because it absorbs radiation. At the same time, aerosols like sulfur, nitrate and organic carbon are emitted by human activities and once in the atmosphere cause global cooling. These particles mask the assessment of the extent of climate warming caused by humans, says Gunnar Myhre of from the Center for International Climate and Environmental Research (CICERO) in Oslo. Myhre’s report was published in Science Express on June 18 and in Science July 10.

Myhre’s research was aimed at resolving a discrepancy between global aerosol models and observation-based estimates to get a more accurate picture of our impact on climate warming. Satellite observations are used to calculate the climate impact from aerosols, Science Daily said. Some estimates indicate that aerosols have masked upwards of 50 percent of climate warming from carbon dioxide, it said. However, Myhre suggests that there may have been a defect in the estimates. He sought to reconcile somewhat the discrepancy between models and estimates from observations, Science Daily reports. Myhre said the estimates are not able to account for the portion of black carbon particles that have grown at a much faster rate than all of the particles.

Myhre concludes that the earlier discrepancy between models and observation-based estimates is due to the fact that the increase in black carbons is much larger than the overall increase in amount of aerosols.

This is important because, as Myhre says, particles only remain in the atmosphere for a few days whereas carbon dioxide stays in the atmosphere for several hundred years. As carbon dioxide emissions increase, climate warming will grow significantly, he says. Aerosols’ effect of masking warming will lessen, Myhre says.

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