Wednesday, October 24, 2007

Seeding the Stratosphere: Is it Cool?

After a long blogging hiatus for fundraising, here's one prevailing view on on how to combat global warming:

Block some of the sun's rays from reaching earth.

That's what happens after major volcanic events, such as the 1991 eruption of Mount Pinatubo in the Philippines.

Fine ash and gases blasted high into the stratosphere, and the large volcanic cloud drifted around the world. It bore 22 million tons of sulfur dioxide, which combined with water to form droplets of sulfuric acid - and that blocked some sunlight from reaching the Earth. The result? A cooler world, with temperatures in some regions dropping by as much as 0.5 degrees C. (Source: USGS)

That was mild compared to the climate change effected by the biggest volcanic eruption ever recorded in human history. Nearly 200 years ago, in the middle of the Indonesian archipelago, Mount Tambora blew - the explosion was 10 times bigger than Krakatoa and more than 100 times bigger than Vesuvius or Mount St. Helens. Approximately 100,000 died in its shadow.

Tambora appears serene in these images from an airplane (top left) and from the space shuttle (top right).
Top left image courtesy of Rizal Dasoeki,Volcanological Survey of Indonesia. Top right image courtesy of NASA. Map courtesy of Tom Ford.

This week NPR's Michael Sullivan investigated Tambora's impact on global climate.

The gas cloud from the 1815 eruption was about 20 times larger than that of Pinatubo, and produced the "year without summer." Average global temperatures decreased about 0.4–0.7 °C (0.7–1.3 °F). On 6 June 1816, snow fell in Albany, New York, and Dennysville, Maine. Such conditions occurred for at least three months and ruined most agricultural crops in North America. Canada experienced extreme cold during that summer. One foot of snow accumulated near Quebec City from 6 to 10 June 1816. (source)

Crops failed and people starved. Hundreds of thousands of people died. People were reduced to eating rats and fighting over roots. Most of these people were killed by epidemic diseases and other things related to starvation. They simply couldn't find enough food.

Yet some scientists believe that artificially creating these post-eruption stratospheric conditions is desirable: they see it as the answer to the global warming situation.

Ken Caldeira of the Carnegie Institution’s department of global ecology advocates this in a New York Times opinion piece today.

In How to Cool the Globe, he writes:

"If we could pour a five-gallon bucket’s worth of sulfate particles per second into the stratosphere, it might be enough to keep the earth from warming for 50 years. Tossing twice as much up there could protect us into the next century.

"A 1992 report from the National Academy of Sciences suggests that naval artillery, rockets and aircraft exhaust could all be used to send the particles up. The least expensive option might be to use a fire hose suspended from a series of balloons. Scientists have yet to analyze the engineering involved, but the hurdles appear surmountable.

"Seeding the stratosphere might not work perfectly. But it would be cheap and easy enough and is worth investigating."

Another proponent of this action is Dutch 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 paper is published in the August issue of the Springer journal Climatic Change, devoted this month to the controversial field of geoengineering.

Why should we consider Crutzen's plan?

"Given the grossly disappointing international political response to the required greenhouse gas emissions,…research on the feasibility and environmental consequences of climate engineering of the kind presented in this paper, which might need to be deployed in future, should not be tabooed,” he says. (More at Science Daily and on the BBC News article, Creating a Sulphur 'Screen'.)

Not everyone is on board. In the NPR piece, University of Rhode Island volcanologist Haraldur Sigurdsson said, "Do you want to counter one pollutant with another one? I don't think so."

These concerns are not new. A decade and a half ago, Tulane University mechanical engineer Robert Watts worried about the unknown potential side effects of geoengineering. "All of these things might have unintended consequences." Watts said: "We really don't understand the climate well enough, so we don't want to start something where the cure might be worse than the disease."

(Watts edited the proceedings of a 1992 conference on the subject called The Engineering Response to Global Climate Change - here's more on his book.)

Caldeira's view: "Which is the more environmentally sensitive thing to do: let the Greenland ice sheet collapse and polar bears become extinct, or throw a little sulfate in the stratosphere? The second option is at least worth looking into."

Caldeira does note that stratospheric seeding should only be viewed as "an insurance policy, a backup plan for climate change." He says having this option is not permission to give up trying to reduce greenhouse gas emissions. Likewise, Crutzen says his experiment should only be used as an emergency measure: it “should not be used to justify inadequate climate policies but merely to create a possibility to combat potentially drastic climate heating.”

Caldeira: "Ninety-nine percent of the $3 billion federal Climate Change Technology Program should still go toward developing climate-friendly energy systems. But 1 percent of that money could be put toward working out geoengineered climate fixes like sulfate particles in the atmosphere, and developing the understanding we need to ensure that they wouldn’t just make matters worse."

Wait - putting sulfur into the atmosphere - isn't that what we've been telling power plants to stop doing? Haven't we heard for years that sulfur dioxide is "a deadly gas...toxic to communities near power plants? Have we not been told that sulfate particulate is unhealthy - fine particles that pollute our communities and places hundreds of miles away, and sulfuric acid that damages our environment? (Clean Air Task Force) Hmm...I'll have to think a bit more about this.

Whatever scientists and politicians choose to do, they'd better do it quick.

Note: stratosphere seeding is only one geoengineering scheme. Read about other proposals here.