Calls for curbs on ozone-forming pollutants

The rarified air of Switzerland's Jungfraujoch helps scientists understand the effects of pollution on the environment. Jungfraujoch research station

Scientists meeting in the Swiss resort of Interlaken are examining the role of ozone in climate change.

They have called for an international agreement – along the lines of the Kyoto Protocol – to reduce the emission of pollutants, which lead to the formation of the gas.

Until now, international attention has focused on ozone depletion in the stratosphere, the layer of atmosphere which lies about 10-50 kilometres above the Earth.

However, the Interlaken meeting is focusing on ozone in the troposphere – the layer of atmosphere, which surrounds us and extends up to about ten kilometres in altitude.

Unanswered questions

“We need to understand how it is produced and how it is destroyed, where it is coming from and where it is going to,” said Guy Brasseur, director of the Max Planck Institute of Meteorology in Hamburg, Germany.

“Tropospheric ozone plays a role in climate production because ozone is a greenhouse gas. Because it is an oxidant, it also determines the way a lot of pollutants are destroyed so it is very important that we maintain our ozone in the troposphere at the present level because it participates in all the global environmental balances.”

It’s only in the last ten years that scientists have really begun to appreciate how closely the ozone problem is related to the climate problem.

Ozone is now ranked the third most important climate gas after carbon dioxide and methane, and some scientists believe it may even come second to carbon dioxide in its effects on climate change.

Measurements from ice cores have provided invaluable data about carbon dioxide levels in the past but this system does not work for ozone because it is too reactive.

“The only way we can get at it is trying to understand what’s going on now and then make estimates of what may have been going on 100 years ago in terms of how much human beings were putting into the atmosphere,” Professor Stuart Penkett of the University of East Anglia in Britain told swissinfo.

Jungfraujoch research

Penkett and his students have been running experiments at the Jungfraujoch research station in the Bernese Oberland since 1996 to try and assess the impact of ozone on the current climate system.

Scientists are particularly keen to know how much ozone in the troposphere is made from pollutants and how much comes down from the stratosphere where most atmospheric ozone – a naturally occurring gas that filters the sun’s ultraviolet radiation – is concentrated.

“We don’t quite know how much ozone we had 100 or 150 years ago because we had almost no measurements and not knowing what is the natural ozone layer it’s very difficult to say how much it has changed but we believe that in the northern hemisphere, the ozone concentration has more than doubled in the last 100 years,” Brasseur told swissinfo.

“That is a big change from a global environmental point of view. It is possible that in regions of high pollution like western Europe, north-west China, Japan and the east coast of the United States, the ozone has maybe increased in the summer time by a factor of three to five.”

International agreement

Ozone is not included in the1997 Kyoto protocol, which seeks to reduce emissions of six greenhouse gases including carbon dioxide and methane in the 39 industrialised countries concerned.

Each of these countries is to pursue the goal of cutting its emissions (expressed as carbon dioxide equivalents) by a given percentage compared with the 1990 baseline. For Switzerland, it is an eight per cent reduction.

Scientists would like to see an international agreement, which seeks to reduce the emission of a number of chemicals which under solar radiation convert to ozone.

“We need to mitigate these emissions and take action so that carbon monoxide, nitrogen oxide, methane and hydrocarbons are not emitted in too large quantities,” said Brasseur.

The four-day meeting in Interlaken, which includes participants from Europe, Japan and the US, continues until Thursday.

by Vincent Landon