One of the many methods for cooling the planet would cause an undesirable destruction of ozone over Antarctica. So then which other methods of planet cooling would avoid this problem?
BOULDER--A much-discussed idea to offset global warming by injecting sulfate particles into the stratosphere would have a drastic impact on Earth's protective ozone layer, new research concludes. The study, led by Simone Tilmes of the National Center for Atmospheric Research (NCAR), warns that such an approach might delay the recovery of the Antarctic ozone hole by decades and cause significant ozone loss over the Arctic.
The study will be published Thursday in Science Express. It was funded by the National Science Foundation, which is NCAR's principal sponsor, as well as by NASA and European funding agencies.
"Our research indicates that trying to artificially cool off the planet could have perilous side effects," Tilmes says. "While climate change is a major threat, more research is required before society attempts global geoengineering solutions."
In recent years, climate scientists have studied "geoengineering" proposals to cool the planet and mitigate the most severe impacts of global warming. Such plans could be in addition to efforts to reduce greenhouse gas emissions. 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. The goal would be to cool Earth's surface, much as sulfur particles from major volcanic eruptions in the past have resulted in reduced surface temperatures.
Why aren't governments regulating the emissions of volcanoes? Shouldn't volcanoes have to apply for a permit to do a very polluting eruption? I'm just asking.
Simone Tilmes and co-workers already knew about the problem caused by sulfates from volcanoes. So they had reason to try to model the effects when sulfates would be released intentionally by humans.
To determine the relationship between sulfates and ozone loss, the authors used a combination of measurements and computer simulations. They then estimated future ozone loss by looking at two geoengineering schemes--one that would use volcanic-sized sulfates and a second that would use much smaller injections.
The study found that injections of small particles, over the next 20 years, could reduce the ozone layer by 100 to 230 Dobson Units. This would represent a significant loss of ozone because the average thickness of the ozone layer in the Northern Hemisphere is 300 to 450 Dobson Units. (A Dobson Unit is equivalent to the number of ozone molecules that would create a layer 0.01 millimeters thick under conditions at Earth's surface).
With large particles, the Arctic loss would range from 70 to 150 Dobson Units. In each case, the larger figure is correlated with colder winters.
But if rising CO2 emissions are going to bring on a global warming disaster then a partial loss of ozone might be a price worth paying to prevent it. However, note that these researchers studied the effects of sulfates which are already thought to destroy ozone when released by volcanoes. We have other choices. Gregory Benford proposes the use of silicon dioxide as the preferred cooling agent. Will Benford's proposal run into the same problem? Does silicon dioxide interact with ozone? It is a really cheap way to do a world wide cooling.
Another method of cooling the planet uses enhanced dimethyl sulfide (DMS) production from marine phytoplankton. Salt the oceans with iron and let nature produce the cooling agent. This happens naturally all the time. Will it damage ozone?
|Share |||Randall Parker, 2008 April 27 01:20 PM Climate Engineering|