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Cash for Climate

How to get your money's worth on climate change geoengineering

Ronald Bailey
August 11, 2009

Let's say the world will spend $250 billion a year for the next 10 years to minimize the suffering caused by climate change. What's the best bargain we can get for the money?

The Copenhagen Consensus Center (CCC), a think-tank in Denmark headed by Skeptical Environmentalist Bjorn Lomborg, has commissioned 21 papers from leading climate experts and economists to answer that very question. Over the coming month, the CCC will be looking at the benefits and costs of proposed actions in four different areas: climate engineering, cutting future greenhouse gas emissions, economic growth, and green energy technologies. Each topic will feature a main research paper accompanied by a series of critiques by other experts called perspective papers.

At the end of the process, the CCC will assemble a panel of five leading economists, three of them Nobelists, to rank all of the proposed solutions as to their relative cost-effectiveness. This ranking process is the CCC's specialty—it has twice used this technique to rank order various proposals for solving some of the world's biggest problems, including disease eradication, sanitation, economic development, malnutrition, and the oppression of women.

This week, the CCC kicked off the process with the high-tech topic of climate engineering, starting with a paper by J. Eric Bickel, an assistant professor at the University of Texas at Austin in Operations Research and a fellow in the Center for International Energy and Environmental Policy, and Lee Lane, a resident fellow at the American Enterprise Institute in Washington, D.C., where he also serves as the co-director of the Institute's Geoengineering Project. Bickel and Lane accept that global warming poses some risks to humanity and use cost-benefit analysis to weigh various proposals for engineering global climate. The chief question that they address is how much research and development funding should be devoted to investigating the feasibility of climate engineering.

The two geoengineering options to manage climate change that Bickel and Lane consider are blocking sunlight or capturing carbon. They favor blocking sunlight—or solar radiation management—over taking carbon out of the atmosphere—or air capture. Bickel and Lane estimate the costs of various solar radiation management scenarios that would offset 0.6° C, 1.3° C, and 1.9° C of future warming, and find that the benefits of deploying some proposed solar radiation management techniques outweigh the costs by between $4 and $18 trillion. (Assuming the calculations of Dynamic Integrated Model of Climate and Economics developed by Yale University economist William Nordhaus, which suggests that the 200-year present value of climate damages would be about $22 trillion, are in the right ballpark.) Air capture involves technologies that would remove ambient carbon dioxide from the atmosphere and most likely bury it underground. Bickel and Lane argue that air capture technologies are too expensive and so do not spend a great deal of time on the topic.

The planet is warming because greenhouse gases like carbon dioxide re-radiate heat from the sun back toward the earth as it tries to escape into space. Solar radiation management techniques aim to increase the amount of sunlight radiated back into space in order to lower the globe's temperature. Bickel and Lane look at proposals that would purposely inject sulfur or other reflective particles into the stratosphere on an ongoing basis to counter the effects of man-made global warming.

This phenomenon sometimes occurs naturally. Volcanoes occasionally inject sulfur particles high into the stratosphere 8 to 12 miles above the earth's surface where they reflect sunlight back into space cooling the planet. For example, when Mount Pinatubo erupted in 1991 in the Philippines, it injected huge amounts of sulfur particles into the stratosphere lowering the globe's average temperature by about 0.5° C for the next year.

The priciest option that Bickel and Lane analyze is a proposal to install a sunshade involving about 4 trillion autonomous "flyers" placed at about 1 million miles in space to dim the sunlight before it reaches the earth. To offset temperatures by 0.6° C, it would take 4 trillion flyers, each about 400-inches square, and weighing a total of 5 million tons. Assuming each launch could carry 800,000 flyers up at a time, that would mean 5 million launches. If a launch occurred every 5 minutes, the entire sunshade could be in place in about 50 years. Using current numbers for launch and satellite manufacturing costs, the sunshade would cost $135 trillion to make and $395 trillion to get it into space. These costs greatly exceed mainstream estimates of the damages that might be caused by climate change. In fact, those figures add up to about 10 times the size of the current world GDP.

Stratospheric aerosols are next up for consideration. Bickel and Lane report that one recent study suggested it would be possible to use a fleet of 167 F-15 airplanes flying three times per day to inject about 1 billion million tons of sulfur particles into the stratosphere each year. This would cost about $4.2 billion per year. The same study calculated firing 8,000 artillery shells daily loaded with sulfur into the stratosphere would cost about $30 billion annually or launching 37,000 stratospheric balloons daily would cost between $21 billion and 30 billion per year. Bickel and Lane calculate that the benefit-cost ratio for using artillery shells to loft aerosols into the stratosphere is 27 to 1. The F-15 option's benefit-cost ratio would be even more favorable.

The third solar radiation management technique Bickel and Lane consider is marine cloud whitening, a proposal that involves hundreds of ships cruising the world's oceans spewing salt water as a mist into the atmosphere. The salt particles would function as cloud condensation nuclei which would increase the extent and brightness of low level clouds over the oceans. These clouds would reflect sunlight back into space cooling the earth's surface.

In this case, to offset 0.6° C of warming would involve 284 ships spewing salt water into the air at a cost of $1 billion per year. To reduce future temperatures by 1.9° C, 1881 vessels would have to be deployed at a cost of $5.8 billion annually. Bickel and Lane calculate that the benefit-cost ratios for cloud whitening range from 7,000-to-1 to 2,500-to-1.

On the strength of these high benefit-cost ratios, Bickel and Lane argue that the Copenhagen Consensus panel of economists should allocate an average of 0.3 percent of its $250 billion climate change budget ($750 million per year) to solar radiation management and air capture research over the next decade. 

To help the final panel in their evaluations, the CCC commissioned two critiques of the Bickel and Lane paper. In her perspective paper critiquing Bickel and Lane's assessment of climate engineering, Anne E. Smith, an economist who heads up the climate and sustainability practice at the consultancy Charles River Associates, delves deeper into the uncertainties about the benefits and costs of solar radiation management. One important goal of R&D into solar radiation management is to reduce uncertainties about its risks.

A remarkably interesting observation by Smith is that such research will have no value to people who are inclined to have positive views about climate engineering. This is because partisans of the technique will tend to dismiss research that suggest that it poses higher risks as false alarms. On the other hand, research might also have no information value because it will never be good enough to convince hyper-cautious people that geoengineering is safe. Finally, Smith opines that Bickel and Lane have given air capture too short shrift and that it could serve as a backup option should new costly risks emerge after solar radiation management has been deployed.

The second perspective paper, from University of Colorado environmental studies professor Roger Pielke, Jr. takes a harder look at the costs and benefits of air capture of carbon dioxide from the atmosphere. Among other reasons, Pielke favors air capture over solar radiation management because it meets the three rules for technological fixes, which are quite useful and worth examining in more detail here.

The first rule is that the technology must largely embody the cause-effect relationship connecting problem to solution. In this case, solar radiation management fails because it addresses the effect of higher average global temperatures rather than the cause, which is accumulating concentrations of greenhouse gases in the atmosphere. On the other hand, air capture aims to remove the cause—e.g., greenhouse gases—from the atmosphere thus preventing an increase in temperature.

The second rule is that the effects of the technological fix must be assessable using relatively unambiguous or uncontroversial criteria. Air capture clearly meets this criterion. Pielke notes, "If the accumulation of carbon dioxide in the atmosphere is judged to be a problem, then its removal logically follows as a solution."

The third rule of technological fixes is that research and development is most likely to contribute decisively to solving a social problem when it focuses on improving a standardized technical core that already exists. In this case, Pielke argues that air capture technologies have been developed now that can be refined and deployed with no risk to the climate system.

To assess the costs of air capture Pielke points out that various estimates for reducing the emissions of carbon dioxide might cost between 1 to 3 percent of total global GDP over the next century. Assuming about 3 percent global GDP growth to 2100, Pielke calculates that the cost of air capture at even $500 per ton of carbon would cost 2.7 percent of global GDP if the goal is to make sure that carbon dioxide concentrations do not exceed 450 parts per million. Pielke concludes, "My bottom line is that the geoengineering of the earth system as a way to adapt to increasing concentrations of greenhouse gases is a losing proposition."

Despite the cautions of Smith and Pielke, it is hard to disagree with Bickel and Lane's conclusion on climate engineering: "The results of this initial benefit-cost analysis place the burden of proof squarely on the shoulders of those who would prevent such research."

Note: I will be reporting on the Copenhagen Consensus Center's next series of papers dealing with climate mitigation, adaptation, and green energy research as they are publicly released.

Ronald Bailey is Reason magazine's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books. This column first appeared at

Disclosure: The Copenhagen Consensus Center paid my travel expenses to report on its Consensus 2008 process. The Center exercised no editorial control whatsoever over my reporting.

Ronald Bailey is Science Correspondent

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