NZ study finds good news for clean air

Air pollution such as this from the Nikola Tesla power plant near Belgrade would be worse without the work of hydroxyl. Picture / Reuters

New Zealand scientists have injected some good news into the gloom and doom of global warming by proving the atmosphere's natural cleaning agent is still doing its good work.

A paper published today in one of the world's top science journals, Nature, shows hydroxyl, a reactive molecule of water which acts as a bleaching agent of nasty gases and hydrocarbons in the air, has remained the same over the past 13 years.

A research team from the National Institute of Water and Atmospheric Research used two measuring sites at Baring Head near Wellington and Scott Base in Antarctica to estimate hydroxyl levels.

The scientists found that after the Mt Pinatubo eruption in the Philippines in 1991 and extensive fires in Indonesia in 1997, hydroxyl levels bounced back within 18 months to previous levels after initially falling.

"If the level of hydroxyl was changing, then we might be in real trouble, but the interesting thing is levels recovered," said Niwa scientist Dr Bill Allan.

Hydroxyl cleans up the second most important greenhouse gas, methane, and nasty hydrocarbons in the atmosphere.

Dr Dave Lowe said although hydroxyl did not clean up the worst greenhouse gas, carbon dioxide, it was vital to life on Earth.

"At any one time it makes up a trillionth of the atmosphere but without it the planet would be choked by smog," he said. "The fact hydroxyl is not decreasing may be one small piece of good news in a pretty bleak scientific consensus on climate change."

Dr Allan said while global warming was bad, it was happening over the next century or so. If hydroxyl suddenly disappeared, the Earth's future could be threatened in much less than 100 years.

Atmospheric chemists have struggled to estimate the amount of hydroxyl in the atmosphere because it is present in such tiny amounts and lasts for just one second. But the team analysed and measured carbon monoxide containing radiocarbon CO14, a "proxy" for hydroxyl which reacts with it and lasts for a few months.

They used the clean air sites at Wellington and Antarctica as baseline measurements because the amount of pollution in the Northern Hemisphere would have made readings far more complex. Dr Lowe said although the study showed there was no long-term trend of hydroxyl depletion in the Southern Hemisphere, it also revealed it was more variable than suspected.

"It appears the atmosphere is subject to quite large changes but is regulating itself in some way that scientists do not yet fully understand," he said.