Cleaner air may make global warming worse


IT MAY seem perverse but cleaning up our air pollution problem is going to increase global warming. The cleaner the air over our cities, the more pronounced the warming effect, according to research.

An Irish scientist at NUI Galway originally initiated the research into how air pollution has a hidden beneficial side. It shows the haze that forms due to pollution, the tiny particles discharged by motor transport, and smoke from burning help to reflect back some of the solar radiation that is warming our climate.

If we manage to clean up the pollution we may also ramp up warming, said Prof Colin O’Dowd, professor of physics at Galway and also director of the Centre for Climate and Air Pollution Studies at the Ryan Institute.

He got a project running under the commission-funded European integrated project on aerosol cloud, climate and air quality interaction. It involved scientists in 48 research institutes in 24 countries and was led by Prof Markku Kulmala of the University of Helsinki.

“We have been studying the interaction between air pollution and climate change with a focus on aerosols and particulate matter,” he said yesterday. “Greenhouse gas emissions are rising which are leading to global warming. But pollution is rising too and this is masking the greenhouse effect.”

The results are shocking given their calculations on this masking, published yesterday in Atmospheric Physics and Chemistry. Cleaner air could increase average global temperatures by 1 degree globally and by between 2-4 degrees over Europe.

“The warming may be even larger,” Prof O’Dowd said.

“With better air quality and cleaning up aerosol emissions we are removing this haze layer which has a cooling effect,” he said. “It demonstrates the need to control air pollution but also have greenhouse gas abatement strategies.”

The research team was not advocating allowing the pollution to remain as a way to control global warming, he stressed. Yet some scientists had advocated “geoengineering”, creating natural hazes by seeding the stratosphere with clean aerosols or creating them from sea water. He was not in favour of such approaches given uncertainty about hidden effects.

“The bottom line is it comes down to economics. What will the economic cost be of poorer health and reduced life-span versus the cost of reducing greenhouse gas emissions?”