April 25, 2008

‘Geoengineering’ Could Damage Ozone Layer

A proposed method of injecting sulfate particles into the stratosphere in order to fight the effects of global warming, would have a drastic impact on Earth's protective ozone layer, researchers said in a new study.

Simone Tilmes of the National Center for Atmospheric Research (NCAR) and colleagues conducted the study, which was published Thursday in Science Express.

Researchers looked at the possible effects of "geoengineering" methods of cancelling out the impacts of global warming.

One of the most discussed ideas, analyzed by Nobel laureate Paul Crutzen and other researchers, would be to regularly inject large amounts of Sun-blocking sulfate particles into the stratosphere.

Sulfur particles from volcanic eruptions have shown a reduction in the surface temperatures of the Earth, however Tilmes said more time is needed to plan before action is taken.

"Our research indicates that trying to artificially cool off the planet could have perilous side effects," said Tilmes. "While climate change is a major threat, more research is required before society attempts global geoengineering solutions."

Researchers implied that over the next few decades, hypothetical artificial injections of sulfates likely would destroy between about one-fourth to three-fourths of the ozone layer above the Arctic. This would affect a large part of the Northern Hemisphere because of atmospheric circulation patterns.

Although temperatures have been rising worldwide, the interior region of Antarctica has actually cooled in summer, which researchers attribute to the depletion of ozone overhead.

"If the successful control of ozone-depleting substances allows for a full recovery of the ozone hole over Antarctica, we may finally see the interior of Antarctica begin to warm with the rest of the world," said Judith Perlwitz of the Cooperative Institute for Research in Environmental Sciences, a joint institute of CU-Boulder and NOAA.

By using a supercomputer from NASA, researchers were able to create a model of interactions between the climate and stratospheric ozone chemistry.

A return to pre-1969 ozone levels would mean atmospheric circulation patterns now shielding the Antarctic interior from warmer air to the north will begin to break down during the summer, they concluded.

The sulfates would also delay the expected recovery of the ozone hole over the Antarctic by about 30 to 70 years, or until at least the last decade of this century, the authors conclude.

"This study highlights another connection between global warming and ozone depletion," said co-author Ross Salawitch of the University of Maryland.

"These traditionally had been thought of as separate problems but are now increasingly recognized to be coupled in subtle, yet profoundly important, manners."

The Intergovernmental Panel on Climate Change and the Kyoto agreement have worked to help countries reduce their greenhouse gas emissions. Some countries, particularly in Europe, have taken steps to reduce emissions.

But carbon dioxide emissions, primarily from burning fossil fuels such as coal, oil and gas have continued to increase.

Since 2000, annual increases of two parts per million or more have been common, compared with 1.5 ppm per year in the 1980s and less than one ppm per year during the 1960s, NOAA's Earth System Research Laboratory said. Last year the increase was 2.4 parts per million.

The study received funding from the National Science Foundation, which is also NCAR's principal sponsor, as well as NASA and European funding agencies.


On the Net:

The National Center for Atmospheric Research

Science Express

Original Press Release - Stratospheric Injections to Counter Global Warming Could Damage Ozone Layer

Companion Article: NOAA Reports Annual Increase of Greenhouse Gases