Proposals to cool down the Earth's climate with high-risk chemical or mechanical technologies have been largely dismissed in the debate over global warming, but a panel of the nation's top scientists say the time has come to significantly increase research efforts and prepare to step in should there be a climate catastrophe.
The most exhaustive U.S. examination of direct intervention in the Earth's climate was released Tuesday by the National Research Council in two reports that assessed the significant costs and risks of such ideas as removing carbon dioxide from the air with massive machines, fertilizing the oceans to increase plant activity, chemically modifying the atmosphere to reflect more sunlight back to space and a wide range of other ideas.
"Let's hope it never happens, but if we ever have our back against the wall we will know ahead of time what we need to do," said Marcia McNutt, chair of the committee and editor in chief of Science magazine. "There are no silver bullets for the current climate situation that comes from any kind of climate intervention. We agree with the majority of people that these are not solutions that we want to turn to."
Indeed, McNutt and a large group of the nation's top academic scientists who wrote the reports said the best approach to the problem of global warming continues to be reductions of greenhouse gases.
The lack of progress for more than two decades, however, makes it "increasingly likely that as a society we will need to deploy" some forms of the least-risky technologies to reduce the Earth's temperature, they said.
The scientists acknowledge that developing risky tools to counteract global warming carries a "moral hazard," in which nations may become even less motivated than they are now to take immediate steps to combat climate change. But not having the tools in hand might also result in future actions without adequate scientific research.
"People are going to read these reports and they are going to be very scared about the future," McNutt said.
The research council's work was divided into two lengthy reports, one that assessed a very high cost and relatively low-risk approach of removing carbon dioxide from the atmosphere.
Isolating carbon dioxide at power plants and injecting it into deep wells remains expensive and unproven at the scale that would be necessary to have a big impact, the report said. Even seemingly benign ideas like reforesting large tracts of land might reduce greenhouse gases, but also cut food production and alter human diets.
And direct reduction of carbon dioxide is not only expensive, but could take centuries to have an effect on temperatures. If carbon dioxide is sharply reduced in the air, the world's oceans would release some of their massive stores to offset the improvement.
A much faster and lower-cost emergency approach would involve changing the Earth's albedo, or the amount of solar radiation that is directed back into space.
The most-discussed approach involves injecting aerosols into the upper atmosphere, similar to the action of a volcano when it releases sulfur dioxide. After the 1991 eruption of Mt. Pinatubo in the Philippines, 20 million tons of the gas entered the atmosphere and the Earth cooled by about 5 degrees over the next three years.
But the risks of albedo modification are very high because it is not well understood and could have unintended consequences, the authors say. It also would not address one of the major consequences of global warming — the increasing acidification of the oceans. And while the average temperature of the globe may drop, the effect would not be uniform.
McNutt said that such a program, if it were undertaken, would not restore Earth's climate to the past. Some regions could actually grow even warmer and rainfall patterns could be disrupted. She said humans — from Southern California to New England — have adapted their lifestyles, homes and infrastructures to specific climates, all of which could be upended.
The technologies at issue have long been on the fringe of the climate-change debate. Many policymakers have considered them an unrealistic approach to a pressing problem. Most geoengineering technology is untested and critics warn that some techniques could end up causing more problems for the environment than they solve. As a result, not much money has been allocated to researching the area.
The U.S. is currently spending $4 billion on climate research, but just $100 million of that money goes to areas relevant to climate intervention and just $2 million to albedo research. The report does not say how much more money should be devoted to the technologies, but it should be more than the current one-tenth of 1%, McNutt said.
The reports devoted a full chapter to reviewing the prognosis for the climate, noting that the average temperature could rise by about 10 degrees by the end of the century or as little as 1 degree. Concentrations of carbon dioxide in the atmosphere have reached as high as 400 parts per million, up from 320 in 1960s.
One report urges that the government create controls that would set clear guidelines on experimentation, as well as prepare for the international agreements in case intervention becomes necessary. It also warns that the technologies "present serious known and possible unknown environmental, social, and political risks, including the possibility of being deployed unilaterally."
But the fight against global warming is becoming increasingly urgent. As the National Research Council dived into its investigation on geoengineering many months ago, scientists said governments could not afford to overlook any options.
"That scientists are even considering technological interventions should be a wake-up call that we need to do more now to reduce emissions, which is the most effective, least risky way to combat climate change," McNutt, a former director of the U.S. Geological Survey, said in a statement. "The longer we wait, the more likely it will become that we will need to deploy some forms of carbon dioxide removal to avoid the worst impacts of climate change."
Vartabedian reported from Los Angeles and Halper from Washington.
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