Thinking Big on Global Warming

Actually, there is. One approach rarely discussed at global warming conferences is to develop capabilities for increasing the fraction of sunlight that is reflected outward by the upper atmosphere back into space. This approach is called "climate geo-engineering." Expressed in terms of the metaphor of the "greenhouse effect," it would work like this: Geo-engineering would put a "parasol" over the greenhouse to deflect 1% or 2% of the sunlight that now affects the Earth. Scattering this small fraction into space would reduce global warming. In the language of climate science, we would increase by a few percent the Earth's "albedo" -- the ratio of incoming sunlight reflected back into space relative to the total inbound from the sun.

We know it would work because it happens naturally all the time. Clouds routinely deflect sunlight and thereby cool the Earth. Volcanoes -- when they erupt and inject millions of tons of fine particulate material into the stratosphere (mostly sulfate aerosols) -- have also cooled large regions of the globe. Mount Pinatubo in the Philippines erupted in 1991 and cooled most of the Earth for a few years, erasing for a short time roughly half of the global warming that took place during the entire 20th century.

The idea of artificially increasing the Earth's albedo is not new. In 1992, a report by the National Academy of Sciences found the prospect of stratospheric albedo enhancement "feasible, economical, and capable." And there are a great many geo-engineering options apart from adding sulfate aerosols into the stratosphere.

But beware. Do not try to sell climate geo-engineering to committed enemies of fossil fuels. Although several geo-engineering options appear to be highly cost-effective, ideological opposition to them is often fierce. Fashionable blogs are replete with conspiracy theories and misinformed attacks. Because of this intimidating opposition, no serious geo-engineering research programs have been started. And without some small-scale tests, not enough data will be available to assess the benefits, cost and possible harmful side effects of such approaches.

Much could be learned about this other half of the global warming picture with a tiny fraction of the funds that have been allocated to climate-change studies focused on greenhouse gas emissions. Those who now oppose climate geo-engineering should understand that none of the suggested options is meant to be a free-standing, long-term solution to global warming. If the greenhouse effect continued to increase, the geo-engineering measures would not only have to be maintained indefinitely but also be gradually augmented to keep pace. Moreover, accumulating CO2 in the atmosphere would make the oceans harmfully acidic over the next few centuries.

Clearly, we need both: adequately explored geo-engineering options for contingent climate stabilization, and truly effective, practical measures to reduce emissions of greenhouse gases.

Mankind's current energy system evolved during the 20th century as an offspring of the Industrial Revolution. It may take almost as long to replace this system with the novel energy sources and distribution networks that future generations will need. This huge transition would be greatly facilitated if geo-engineering options are developed and tested to provide a safe breathing space without a massive global-warming crisis.

Mr. Iklé, an undersecretary of defense policy for President Ronald Reagan, is with the Center for Strategic & International Studies. Mr. Wood, a research fellow at the Hoover Institution, is affiliated with the Lawrence Livermore National Laboratory and Intellectual Ventures LLC. A version of this article will be published in the January issue of The National Interest.