When Mount Pinatubo erupted in 1991, 10 tons of sulfur were blasted into the stratosphere, which is 10-40 kilometers above the earth's surface. As a result of this eruption, earth's average surface temperature decreased by 0.6 degrees celsius (1 degree Fahrenheit) for two years afterwards.
The plan is to send rockets carrying sulfur up to the stratosphere, where they would explode.
"After the injection at high altitude, it started to move around the globe with the air motions; first in an east-west direction, but also with time in a north-south direction. After about a year, the initial input of pollutants in the stratosphere by the volcano had spread rather evenly around the world," said Nobel Laureate Paul Crutzen.
Crutzen won the Nobel Prize in Chemistry for explaining how earth's ozone layer is formed and destroyed. Partially as a result of his research, world governments banned chlorofluorocarbons (CFCs) that were depleting ozone over Antarctica. CFCs were commonly used in refridgerators and as propellants in aerosols.
Based on the observed effects of the Pinatubo eruption, Crutzen thinks that adding sulfur to the ozone layer will have a protective effect for earth by creating a "blanket" that repels some of the sun's rays (pictured), thereby reducing global warming. However, this idea is controversial because when sulfur is found at lower altitudes, it causes a lot of damage in the form of acid rain. In fact, in the mid-1950s, thousands of people died annually due to respiratory disease caused by sulfur pollution. To reduce this damage, Clean Air Acts were put into effect to reduce sulfur emissions.
"We want to clean up the environment because air pollution is unhealthy," said Crutzen. "But this pollution also cools the Earth by reflecting solar radiation into space."
To avoid more acid rain, Crutzen proposes adding sulfur to high altitudes. Unfortunately, the likely consequences of adding sulfur to the stratosphere are unknown. Even though it would be at very high altitudes, it may give rise to more acid rain, or it may further destroy the ozone layer.
However, Crutzen is more worried about the effects of unmitigated global warming. "I am prepared to lose some bit of ozone if we can prevent major increases of temperature in the future, say beyond two degrees or three degrees," Crutzen says.
Cited story and image source.
.
- Log in to post comments
More like this
How would they add sulfur to the ozone layer?
I would suggest that eggs and other foodstuffs that human gut flora will metabolised to create noxious gasses could be added to the diets of airline passengers, balloonists and astronauts.
Bob
Sulfur aerosols do not stay in the stratosphere. Please see these graphs from the IPCC TAR . The bottom one shows the cooling effects of volcano's, in watts per square meter. The rightmost downward spike on the bottom graph is the cooling effect of Mt Pinatubo. It peaks at about -2.2 watts per square meter, but then rapidly declines, and by 1998 has weakened to -0.4 watts per square meter. By the top graph on the same page, you can see that the forcing of WMGHG (Well-Mixed Green House Gasses) on the climate had already reached +2.3 watts per square meter by about 1998.
If WMGHG levels were maintained at constant 1998 levels, a Mt Pinatubo-sized injection of sulfur aerosols would be needed every few years. (I estimate the average forcing over the final 7 years to be about -1.1 watts per square meter - or about 1/2 the necessary amount to offset 1998 WMGHG levels over the same period.)
That's an awful lot of sulfur to have raining down on us (remember - once it sinks down into the troposphere, it will fall with the next rain.)
The article seems to assume, with no explanation, that stratospheric injection might somehow avoid these problems. But most of the volcanos on graph (d), which I link to above, injection sulfur into the stratosphere, and yet all of them had very short-lived cooling effects. So there's no reason to believe stratospheric injection will prevent the sulfur from returning to earth.
I would like to know what Crutzen's responses to these serious problems are.
10 tons? This must be some kind of a typo; it was more like 20e6. Otherwise, fascinatingly funny.