An Emergency Cooling System for the Planet - Can geoengineering save us from global warming?

Last week, the American Enterprise Institute (AEI) held a conference that asked if geoengineering was a feasible solution to lower our planet's temperature, at least temporarily. The question is what to do if man-made global warming turns out to be a serious problem? At AEI, climatologist Tom Wigley from the National Center for Atmospheric Research in Colorado defined geoengineering as the deliberate modification of the earth's short wave radiation budget in order to reduce the magnitude of climate change. In his presentation, Wigley looked mostly at two possible approaches to geoengineering: injecting sulfate or other aerosols into the stratosphere, and changing the reflectivity of clouds.

Why consider geoengineering in the first place? As Columbia University economist Jeffrey Sachs wrote in Scientific American in April: "[O]ur current technologies cannot support both a decline in carbon dioxide emissions and an expanding global economy. If we try to restrain emissions without a fundamentally new set of technologies, we will end up stifling economic growth, including the development prospects for billions of people."

So if we don't want to perpetuate poverty in the name of preventing climate change, geoengineering may be our way out. Why? Because geoengineering would provide more time for the world's economy to grow while inventors and entrepreneurs develop and deploy new carbon neutral energy sources to replace fossil fuels. Wigley also noted that cutting greenhouse gas emissions is a tremendous global collective action problem. It seems unlikely that fast-growing poor countries like India and China will agree cut back on their use of fossil fuels any time soon. If that's the case, then emissions reductions in rich countries would have almost no effect on future temperature trends. Geoengineering could give humanity more time to resolve this collective action problem, too.

So let's take Wigley's second proposal first—changing the reflectivity of clouds. Researchers know that this can be done because it already happens with ship tracks. Ship exhaust over the oceans injects particles into the atmosphere that serve as cloud condensation nuclei, creating clouds in the wakes of ships. Ship exhaust produces and brightens clouds so that they cool the planet by reflecting sunlight back into space, but only by a little bit. However, recent modeling research by University of Edinburgh engineer Stephen Salter and his colleagues calculates that doubling the number of cloud condensation nuclei would more than compensate for any warming associated with a doubling of carbon dioxide in the atmosphere. This could be accomplished by having ships deliberately inject seawater into the atmosphere where salt particles would serve as extra cloud condensation nuclei.

In 2006, Chemistry Nobelist Paul Crutzen proposed injecting sulfate particles into the stratosphere to reflect some sunlight back into space (an idea discussed by reason contributor Gregory Benford more than ten years ago). This might be done with giant cannons. Crutzen argues that it would cost between $25 and $50 billion per year to shoot enough sulfate particles into the stratosphere to reduce incoming sunlight by 1.8 percent. This would be enough to counter the predicted warming produced by doubling atmospheric carbon dioxide. An earlier study by Yale University economist William Nordhaus estimated that the sulfate injection proposal would cost about $8 billion per year. This compares nicely with the $125 billion per year Nordhaus calculated it would have cost the U.S. to implement the Kyoto Protocol.

Wigley spent most of his time at AEI discussing the possible risks involved with the sulfate injection proposal. Wigley argued that sulfates injected into the stratosphere would be equal to only about 10 percent of those humanity already injects into the lower atmosphere, so this wouldn't greatly boost acid rain. In April, a study by some of Wigley's National Center for Atmospheric Research colleagues found that injecting sulfates would further deplete the ozone layer that shields the earth's surface from damaging ultraviolet light. Wigley simply noted in passing that even more recent research suggests that the damage to the ozone layer will be less than the April study estimated.

Stratospheric sulfate injection might also change rainfall patterns, perhaps reducing precipitation from the monsoons on which millions of Asian farmers are dependent. In response to these worries, Wigley noted that stratospheric sulfates might reduce the intensity of monsoons by two to three percent which contrasts with a current monsoon variability of 30 percent.

But one big problem that sulfate injection would not solve is the continuing acidification of the ocean that is occurring as extra carbon dioxide from the atmosphere dissolves into the seas. This acidification could eventually pose problems for creatures such as mollusks and corals that use calcium carbonate to grow their shells and skeletons.

What is the safe level at which to stabilize carbon dioxide? The current greenhouse gas concentrations are equivalent to 385 parts per million (ppm) of carbon dioxide, up 100 ppm over pre-industrial levels. In the past some researchers suggested that stabilizing concentrations at 550 ppm would avoid the most serious effects of global warming. Now other researchers are arguing that we have to get back to 350 ppm. Wigley sees no signs that humanity is on a track to stabilize carbon dioxide concentrations at 550 ppm. Consequently, he believes that we will have to resort to geoengineering as a way to buy the time humanity needs to figure out how to cut carbon dioxide emissions. He foresees an effort to ramp up stratospheric sulfate injection over 75 years to counter the climatic effects of rising carbon dioxide concentrations.

Stabilization can only be achieved by cutting current carbon dioxide emissions by 80 percent. This means implementing highly unpopular policies of carbon rationing and higher energy prices. So some climate change researchers and environmental activists worry that the public and policymakers will see geoengineering as way to avoid making hard decisions. "If humans perceive an easy technological fix to global warming that allows for 'business as usual,' gathering the national (particularly in the United States and China) and international will to change consumption patterns and energy infrastructure will be even more difficult," writes Rutgers University environmental scientist Alan Robock.

Perhaps. But that is not an argument against pushing ahead with a vigorous research program on geoengineering responses to climate change. Insisting on cuts in carbon dioxide emissions is like trying to require a healthy diet and exercise regimen to prevent heart disease. But when you have a heart attack, you are happy to have a bypass surgeon handy.

Location: > Prometheus: An Order of Magnitude in Cost Estimates: Automatic Decarbonization in the IEA Baseline Archives

June 09, 2008

An Order of Magnitude in Cost Estimates: Automatic Decarbonization in the IEA Baseline

Posted to Author: Pielke Jr., R. | Climate Change | Energy Policy | Technology Policy

Last week I mentioned the conclusions of the IEA Energy Technologies Perspectives report. I have had a chance to look at the full report in some depth, with an eye to the assumptions in the report for the spontaneous decarbonization of the global economy.

All assessments of the costs of stabilizing concentrations of carbon dioxide start with a baseline trajectory of future emissions. The costs of mitigation are calculated with respect to reductions from this baseline. In the Pielke, Wigley, and Green commentary in Nature (PDF) we argued that such baselines typically assume very large, spontaneous decreases in energy intensity (energy per unit GDP). The effect of these assumptions is to decrease the trajectory of the baseline, making the challenge of mitigation much smaller than it would be with assumptions of smaller decreases in energy intensity (and a higher baseline trajectory). Obviously, the smaller the gap between the baseline scenario and the mitigation scenario, the smaller the projected costs of mitigation.

The annotated figure below is from the IEA ETP report (Figure 2.8, p. 74), and shows the assumptions of decreasing energy intensity in the baseline scenario (BASELINE), as well as the two mitigation scenarios (ACT [emissions stabilized at current values] and BLUE [emissions half current values]).

IEA Decarb.jpg

In the annotation I show with the red call out the difference between the BASELINE and BLUE scenarios, which the report identifies with a cost of $45 trillion. The magnitude of this difference is about 0.8% per year. However, the report assumes that about twice this rate of decarbonization of the global economy will happen spontaneously (i.e., the magnitude of the BASELINE reductions in energy intensity). With the green call out I ask how the baseline is actually to be achieved.

In numbers, the BLUE scenario assumes that by 2050 a trajectory consistent with stabilization at 450 ppm carbon dioxide will require reductions in emissions from 62 Gt carbon dioxide to 14 Gt. But what if we use a "frozen technology" baseline as recommended in PWG?

Using the assumptions from Annex B of the report for global economic growth (4.2% to 2015, 3.3% 2015-2030, and 2.6% 2030 to 2050 -- we could play with these assumptions as well) results in a frozen technology baseline of 115 Gt carbon dioxide. Thus, 53Gt of carbon dioxide are assumed in the BASELINE to be reduced by the automatic decarbonization of the global economy. This spontaneous decarbonization will occur without any of the technologies proposed in the report to get from the baseline to the mitigation level (otherwise the report would be double-counting the effects of these technologies). What these technologies are is anyone's guess, as the report does not describe them.

If the world does not automatically decarbonize as projected in the IEA baseline, then the costs of mitigation will be considerably higher. By how much?

If we take the report's marginal cost estimate of $200 to $500 per ton for mitigating carbon dioxide, then a simple estimate of the full costs from a frozen technology baseline would be an additional $210 to $530 trillion above the $45 trillion cited in the report. Yes, you read that right.

What if the assumption of automatic decarbonization was off by only 10%? Then the additional cost would be an additional $21 to $53 billion, or about the same magnitude of the IEA's total cost estimate of mitigation (i.e., of moving from the BASELINE to the BLUE trajectory) .

What does this exercise tell us about costs estimates of mitigation?

1. They are highly sensitive to assumptions.

2. Depending on assumptions, cost estimates could vary by more than an order of magnitude.

3. We won't know the actual costs of mitigation until action is taken and costs are observed. Arguments about assumptions are unresolvable.

Meantime, it will be easy to cherrypick a cost for mitigation -- low or high -- that suits the argument that you'd like to make.

Anyone telling you that they have certainty about the future costs of mitigation -- whether that certainty is about high costs or low costs -- is not reflecting the actual uncertainty. Action on mitigation will have to take place before such certainty is achieved, and modified based on what we learn. Posted on June 9, 2008 02:07 AM

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June 09, 2008

An Order of Magnitude in Cost Estimates: Automatic Decarbonization in the IEA Baseline