July 27, 2006
Sulfur Could Reverse Global Warming

Nobel Prize winning chemist Paul Crutzen says we could cool the planet by injecting sulfur into the atmosphere.

Injecting sulfur into the atmosphere to slow down global warming is worthy of serious consideration, according to Nobel laureate Paul Crutzen from the Max Planck Institute for Chemistry in Germany and the Scripps Institution of Oceanography, University of California at San Diego.  His thought-provoking paper1 is published in the August issue of the Springer journal Climatic Change, devoted this month to the controversial field of geoengineering.

The sulfur would reflect light back into space.

Crutzen’s proposed planet-saving scheme, which artificially injects sulfur into the earth’s stratosphere (the second atmospheric layer closest to earth) to offset greenhouse gas warming, is based on this phenomenon.

His “albedo2 enhancement method”, or, in other words, his proposed way of increasing the earth’s reflective powers so that a significant proportion of solar radiation is reflected back into space, aims to replicate the cooling effect these man-made sulfate particles achieve.

If we get into desperate straits sulfur could be used as an emergency climate treatment. It would require continuous application since the sulfur does not stay in the atmosphere.

In Crutzen’s experiment, artificially enhancing earth’s reflective powers would be achieved by carrying sulfur into the stratosphere on balloons, using artillery guns to release it. In contrast to the slowly developing effects of global warming associated with man-made carbon dioxide emissions, the climatic response of the albedo enhancement method could theoretically start taking effect within six months. The reflective particles could remain in the stratosphere for up to two years.

Would the sulfur cause acidic rains or other problems? How big would those problems be? Volcanoes inject large amounts of sulfur. What other effects does that sulfur cause?

On most issues involving fears of worst case outcomes of human activity my take on them is that we can use technology to prevent or reverse the outcomes. That's not an argument for total complacency. But it is an argument against claiming that civilization is going to collapse or that we are going to suffer terribly.

The best way to cut carbon dioxide emissions is to develop cleaner energy technologies that are cheaper than the dirtier ones. Then we'd get both cheaper energy and a cleaner environment.

Share |      Randall Parker, 2006 July 27 11:35 PM  Climate Engineering

Jim said at July 28, 2006 12:39 PM:

another downside is that uniform reduction in sunlight across the globe would reduce crop yields.

I wonder how large a sheet of mylar you'd need at the equator to offset the effects of global warming? if you suspended it from many helium balloons high in the sky, you'd increase the projected area. would a square mile of mylar at a feasible height work?

Lou Pagnucco said at July 29, 2006 12:13 PM:

Perhaps this experiment is already in progress.

See "Why the Sun seems to be 'dimming'" at the BBC website:

The article starts out:

We are all seeing rather less of the Sun, according to scientists who have been looking
at five decades of sunlight measurements. They have reached the disturbing conclusion that
the amount of solar energy reaching the Earth's surface has been gradually falling.

Paradoxically, the decline in sunlight may mean that global warming is a far greater
threat to society than previously thought.

Apparently sunlight has been reduced in the U.S. by 10% by particulate pollution - the reduction is still
higher in other parts of the world.

A question I have is whether the radiative energy is being thermalized at a higher altitude instead of
simply reflected back into space, resulting in a less dramatic temperature shift than the article indicates.

Another problem, not discussed in the BBC article, is the effect that particulate pollution is having on
ice masses. I've read that the coating of pollution on glaciers is causing them to absorb more heat and melt much faster. This is over and above the impact of global warming.

Engineer-Poet said at August 1, 2006 6:20 PM:

Less intense light seems to improve carbon uptake, if the Keeling curve behavior after the 1991 Pinatubo eruption is any indication.  Or maybe it's the reduction in temperature and thus heat and water stress.  Either way, a little appears to be a good thing.

If other Nobel winners hadn't already talked this up, I could have claimed a scoop.  But anyone who was aware during Pinatubo, or has read about the year without a summer, should have had enough hints to think of it independently.

ryan said at February 13, 2008 9:47 AM:

I really was interested in the sulfur thing and I want to know where you would get all the sulfur, and what about the crops how much food will we lose? When do you think you would try this.

Robert said at July 19, 2008 12:51 PM:

Sulfur seems an odd element to inject as the efforts to reduce acid rain included nearly eliminating sulfur from diesel fuel. The conflicting research on carbon dioxide effects on green plants more likely will lead to more sensible atmospheric stabilization particularly as plant consumption of CO2 is the major actor in releasing oxygen for breathing.

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