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Geoengineering: A Possible Climate Change Insurance Policy?

Michael MacCracken's picture
 A possible Climate Change Insurance Policy

   Photo © ochus b at Flickr under a
   Creative Commons license.

Even if all emissions of greenhouse gases and aerosol precursors ended today, more warming would occur in coming decades than the 0.8°C that has occurred to date, greatly intensifying climate change and its associated impacts. Already, sea level is rising, sea ice and mountain glaciers are retreating, the ranges of plant and animal species are shifting poleward and upward, and the Greenland and Antarctic ice sheets are both losing mass. Each round of the assessments of the Intergovernmental Panel on Climate Change has found that change is occurring more rapidly than previously projected.

With coal, petroleum, and natural gas providing over 80% of the world’s energy, greenhouse gas emissions cannot be stopped today, or next year, or even in a few decades. While international negotiations have the potential to limit emissions and the ultimate changes in climate to be experienced by future generations, much greater changes in climate than have occurred to date are inevitable, and their impacts will continue to intensify. The changes are so rapid and large that it is becoming much more likely that critical thresholds will be exceeded, triggering potentially unstoppable Earth system responses. Most serious would be initiation of large releases of methane from thawing permafrost or sea level rise of over a meter per century as deterioration of the major ice sheets accelerates. The resources required to deal with the consequences if this occurs would be enormous.

While limiting emissions through mitigation is essential and can help slow climate change, the problem is that just reducing emissions will only very slowly limit climate change over the next few decades. And while adaptation is also essential, there are many consequences of climate change for which no practical adaptive response exists—societies will have to suffer, migrate, or find new ways to provide the lost services. With international negotiations moving slowly, the situation continues to become more and more problematic.

The urgency of the situation has resurrected consideration about whether it might be appropriate to not just limit what we are doing to the climate, but, in addition, to attempt to deliberately manipulate the climate and/or atmospheric composition in a way that would counteract the changes being induced by the energy-related emissions of carbon dioxide and other greenhouse gases. This category of effort has been dubbed geoengineering, although it might better be termed georestoring of the climate, because the intent would be to moderate climate change and its impacts.

For example, nations might choose to try to emulate the cooling influence of major volcanic eruptions by, on a continuing basis, augmenting the amount of particulate matter in the stratosphere. Injecting sulfate aerosols globally or at the right latitudes could be done in a way that would reflect an amount of solar radiation equal to the increased trapping of energy by the greenhouse gases. Although this could limit global warming, thus reducing impacts like the loss of sea ice and slow the increase in sea level, there would be several side effects, including whitening of the sky, perhaps altering the course of storm systems, and reducing the efficiency of many types of solar energy systems. While this might seem an acceptable tradeoff today, it is worth noting that future generations would have to continue these injections for centuries, or the warming that was being offset would reappear relatively rapidly. The report, Beyond Mitigation: Potential Options for Counter-Balancing the Climatic and Environmental Consequences of the Rising Concentrations of Greenhouse Gases, just published provides an overview of the range of proposals that have been made over the past few decades.

In addition to limiting global change through mitigation, a conceivable complementary approach could be to augment the international approach could be augmented with specially designed efforts to limit the intensity of specific, particularly severe impacts. In my view, four possible actions deserve intense analysis because the potential losses appear to be far larger than the likely cost of implementation:

  1. Limiting the solar radiation that reaches the Arctic and Antarctic in order to restore conditions needed by the region’s species and to limit sea level rise from the melting of the Greenland and West Antarctic Ice Sheets.
  2. Enhancing uptake of carbon by the ocean, storing it in the deep ocean in order to moderate ocean acidification and limit damage to the marine food web. Alternatively, ocean acidification might be limited in specific areas such as the Great Barrier Reef by adding a buffering compound to ocean waters.
  3. Limiting the warming of the ocean in the regions that contribute to intensification of tropical cyclones (i.e., hurricanes, typhoons, etc.).
  4. Actively managing the global emissions of sulfur dioxide in order to maintain, or even enhance, the global cooling influence of tropospheric aerosols.

Each of these actions, and there may be others worthy of consideration, would focus on intervening to moderate a specific impact. There are viable technological approaches for each of these activities, and they would be readily reversible if unexpected, adverse consequences arose. What is needed now is an aggressive research and development effort that determines the optimum approach, carries out small scale tests, investigates and compares unintended side effects with the impacts of greenhouse gases that are alleviated, and puts forth a near-term plan for active consideration at an appropriate regional or global forum.

None of these actions would be a substitute for aggressive global mitigation of emissions or alleviate all of the adverse consequences. However, they could more evenly spread the burden of global warming and potentially slow the onset of at least some of the irreversible consequences. In this way, geoengineering could buy a small amount of time for global mitigation to be negotiated and take hold. Undertaking research on these impact interventions seems important and timely.
 

Comments

Submitted by Anonymous on
It is a striking feature of planetary convection systems that they exhibit directionality. One of the most significant factors determining climatic conditions on any planet is likely to be the effect of planetary rotation. This force operates independently of temperature and may well be more significant than variability in the chemical composition of atmospheric gas or the liquid of the oceans. In the upper atmosphere or stratosphere the jet stream flows from West to East. This fact is presumably explained by the direction of the earth’s rotation. Closer to the surface of the planet there is a contra-flow system that also exhibits a similar directionality. Water rising in the east falls on the land mass lying to the west. For example, water from the Indian Ocean falls in Africa. Water from the Atlantic falls in Brazil and water from the Pacific falls in Queensland and South Eastern Asia. As a result of such rainfall patterns, the major desert areas tend to lie on the Western side of continental land masses. In Africa there is Namibia and Western Sahara. In the Americas there are the deserts of Chile and California. In Asia much of the desert is found in the south western part of the land mass. A similar directionality exists in the surface liquid of the planet. The Gulf Stream is the best known part of a global conveyer belt of ocean currents that takes 1000 years approx. to circulate the planetary ocean system. The cool high density current flows in an east to west direction, whilst the faster flowing, lower density current flow in a west to east direction. It is a reasonable prediction that a similar conveyor belt must exist in the internal liquid core of the planet. Low density fast moving material will flow from west to east whilst a deeper current of hot dense material will circulate in an east to west direction closer to the centre of the planet. The speed of rotation is presumably fastest in the equatorial or tropical zone. I n regard to weather systems, one therefore finds the active tropical weather systems enclosed by stable high pressure areas in the polar regions. A cross section of the planet shows it to be composed of a gas atmosphere and two liquid zones, the inner core and the oceans. It is probable that this causal mechanism, planetary rotation, dominates the effects of minor variations in temperature or CO2 composition. There are other many factors effecting climate including the distribution of the continental land mass and the seasonal gyration in axis of the planet. The notion that a fractional change in the level of Co2 could have such large effects on climate is intrinsically improbable.

Given the massive movements of the atmosphere and the oceans, and the varied locations of large continents and mountain ranges, it can certainly be hard to imagine that the limited activities of humans can modify the global climate. Yet, we also can observe that the change in location of the warm waters of the Pacific Ocean (called an El Nino) and the gases and dust injected by volcanic eruptions can indeed change global weather and the average global temperature. On even finer scales, we experience the effects of additional water vapor in the atmosphere when we stay warmer through humid nights than night when the air is dry and clear. Earth history also indicates that the CO2 concentration can be different than at present, and that, along with changes in other factors, these changes can contribute to climate change (e.g., the Cretaceous—the time of the dinosaurs—had a CO2 concentration several times as high as today—and palm trees in arctic regions).We also know that the surface of Venus is very hot, and not because it is closer to the Sun—the reason instead is that the atmosphere of Venus has a lot of carbon dioxide, and this large amount traps the solar radiation that is not reflected to space and makes the surface scorching hot (because of its bright clouds—which is why we can see it--Venus absorbs less solar radiation per square meter than the Earth). Studies of all of this have been going on since the 19th century, and the various proposals have since then stood up to withering criticism because they are confirmed by observations, by past climatic behavior, by theoretical analyses, and, yes, by computer models of the Earth’s climate system that are based on the rigorous physical laws of conservation of mass, momentum, energy, etc. (plus some empirically determined relationships). The problem being so complex, the nations of the world created the Intergovernmental Panel on Climate Change to draw together scientific understanding from the scientific community around the world. They have now issued four major assessments that have been accepted UNANIMOUSLY by the nations of the world and also by all of the major national academies of science. So, while the notion of humans causing global warming may seem counter-intuitive and not be completely understood, its basis is very soundly based, as explained in the assessments, and, for policymakers, the risks created are sufficiently clear and serious that it is time (or far past time) that they be addressed in a significant and serious manner.

Submitted by Anonymous on
Dear Michael, Your point is well taken that atmospheric CO2 (parts per million) causes temperature increase. The following graphic http://www.ipcc.ch/graphics/graphics/syr/fig2-3.jpg shows an increase in atmospheric CO2 parts per million for 1960-2000 of 50. It is a simple linear function and one can therefore use simple extrapolation to estimate a figure for the increase in atmospheric CO2 parts per million of 125 per 100 years. Taking a current value of 390 CO2 ppm for 2010 and taking 1760 as the base year for the pre-industrial initial state of CO2 ppm =280, one might thus estimate cumulative atmospheric CO2 as follows: 1760 280 ppm approx. 1960 340 ppm approx. 2010 390 ppm approx. 2060 450 ppm approx. 2110 515 ppm approx. 2145 560 ppm approx. Compare these figures with what the UK government says: “The rate of growth in atmospheric CO2 concentration depends on future fossil fuel usage, and on the ability of the biosphere to absorb CO2. The IPCC SRES scenarios used for UKCP09 all predict emissions of CO2 to increase during the first half of the 21st century, while the land carbon cycle is expected to become less efficient at absorbing CO2 as the climate warms. Consequently, the rate of CO2 build up in the atmosphere over the next 50 years is projected to be higher than in the recent past. There is still substantial uncertainty in the strength of feedbacks between climate and the carbon cycle that determine CO2 uptake, so the UKCP09 projections sample a range of land carbon cycles consistent with current understanding. For the SRES A1B scenario the projected median value for mean atmospheric CO2 concentration for the period 2050-2070 is 600 ppmV. The projected 10-90% range for this period is 520-650 ppmV with A1B forcing. More detailed analysis will be presented in future publications from the Met Office Hadley Centre.” You will note that there is a difference of 150 CO2 ppm between the Hadley centre prediction for atmospheric CO2 and one given above that is based on historical extrapolation of a trend. The UK government and many others have a policy of switching to a low carbon economy. However, the actual advice they get from their own advisers is: 1.The direct effect of burning fossil fuel on atmospheric CO2 is quite small, about 25%-30%. 2.There are many causes of increased atmospheric CO2 that have nothing to do with burning fossil fuel. An increase in solar activity or cutting down a large amount of rain forest could cause increase atmospheric CO2. The science is highly uncertain. 3. There are also causes of temperature increase, other than atmospheric CO2, such as methane, water vapour etc. The science is highly uncertain. 4. Increasing quantities of atmospheric CO2 have a diminishing temperature/greenhouse effect. Therefore, future economic growth is less polluting than past economic growth. So one can establish the “saturation” level of atmospheric CO2 p.p.m. at which carbon use is pollution-free. On this point see: "...This means that a doubling of CO2 from a different value (say, from the present value or from 560 ppm) gives the same forcing as a doubling from 280 ppm. But the response of the climate system, of course, could differ somewhat for different initial states, which is why “doubling from 280 ppm” should be included in any exact definition..." Stefan Ramhstorf, member of IPCC. The basic historical model of the CO2 greenhouse effect is that, starting from the initial pre-industrial level of 280 p.p.m. of atmospheric CO2, a doubling from 280 ppm to 560 ppm has a temperature effect of 3c +/- 1. Leaving aside other factors such as the methane effect, aerosols and claims about water vapour and applying this greenhouse effect for CO2 to the above “historical” estimates of future levels of atmospheric CO2, one can make the following estimates of future temperature increase, based on CO2 emissions alone: For: the period 2010-2060 (390 ppm to 450 ppm) = 60 increase in CO2 ppm At 3c (per doubling of CO2):= 0.64 deg.cent increase. At 4c (per doubling of CO2):= 0.857 deg.cent increase. These values are below the range of the Hadley estimates. If CO2 were the major cause of global warming, the 2c temperature increase that is proposed by the Hadley Centre would require a CO2 ppm increase in the order of 210 ppm over 50 years. This is only possible if non-fossil fuel effects and feedbacks account for 2/3 of the increase in CO2 ppm. It is not fossil fuel and future economic development per se that causes temperature increase. The problem of fossil fuels is not nearly as serious as institutions such as the World Bank suggest. In this context see the recent post: "Is temperature increase good for the planet?" Such posts are merely intended as polemic to ensure a proper balanced debate. Best Regards,ANONYMOUS P.S. I was fascinated by your remarks about Venus. In terms of geo-engineering, could one make it habitable by pumping the Venus atmosphere full of Oxygen? "We also know that the surface of Venus is very hot, and not because it is closer to the Sun—the reason instead is that the atmosphere of Venus has a lot of carbon dioxide, and this large amount traps the solar radiation that is not reflected to space and makes the surface scorching hot (because of its bright clouds—which is why we can see it--Venus absorbs less solar radiation per square meter than the Earth)." M.MacCracken

To Anonymous— I have three primary responses to your comments that I want to cover separately: 1. Projections of changes in the CO2 concentration: The present atmospheric CO2 concentration is about 387 ppm, up from about 280 ppm during preindustrial times, so up about 38%. The rate of increase per year has been accelerating—mostly because the rate of emissions has been increasing—in the 1960s, it was about 1.3 ppm/yr; recently it is about 2.2 ppm/yr. While we do not know exactly what future emissions will be, global emissions have been increasing more rapidly than the highest projected emissions scenario prepared just a decade ago. Your note suggests a linear extrapolation, which is simple, but we really know more than that, given the international energy infrastructure, growing demands for energy, and available energy resources and technologies. Even assuming global emissions remain constant (which is very likely an underestimate given the need for more energy in China, India, and elsewhere) and that ocean and biospheric uptake rates stay the same (and as you note, these rates of uptake might well drop), then the projected increase in CO2 concentration from 2010 to 2060 would be from 390 ppm up to about 500 ppm (not 450 ppm as you suggest). Realistically, if nations cannot reduce emissions, then it is likely that the concentration could well be 550 ppm or higher. And then there are the increasing concentrations of the many other greenhouse gases. The world is in quite a predicament. You are right that cutting down a forest can also lead to an increase in the global CO2 concentration, but the fossil fuel emissions really dominate. There are only about 600 billion tonnes of carbon in above ground vegetation for the world as a whole—at the present rate of emissions, we will burn up that much carbon, we’ll burn that much in about 70 years, and with growing emissions, in even less time—and we will not be destroying all the world’s vegetation. 2. CO2’s warming influence and past changes in climate: First, we are not anywhere near saturating the radiative influence of CO2—we will simply not reach a concentration where adding more CO2 will not exert a further warming influence (recall, that during the Cretaceous, so more than 65,000,000 years ago, the CO2 concentration was likely between 1500-2000 ppm and their were palm trees at Arctic latitudes). So, the world has in the past been a lot warmer, and a higher CO2 concentration had a lot to do with it. It is true that the climate sensitivity is such that the relationship is logarithmic, so the equilibrium warming associated with each CO2 doubling is about the same, but clearly, the world can get a lot warmer. Second, there are several reasons that you cannot simply extrapolate past changes in climate to estimate future change. Even assuming that human factors are the only cause of past changes in climate, there are multiple factors that are affecting the climate—several different greenhouse gases and absorbing aerosols (like soot) are exerting a warming influence, and reflective aerosols (like sulfate) are exerting a cooling influence—and the absolute and relative influences of these factors have been changing in time. For the future, the cooling influence of sulfate aerosols is likely to decrease (as air quality is improved), thus uncovering the warming influence of greenhouse gases that have been offset by sulfates. In addition, the concentrations of greenhouse gases are building up because their atmospheric lifetimes are very long (for CO2, some of the perturbation will last for millennia). So, a simple linear extrapolation is just not going to be a reliable projection of the warming influence of human activities. Third, the response of the climate system to the increasing concentrations of greenhouse gases is slowed by the time it takes for the oceans to warm (and for some other adjustments to occur). So, you cannot just suggest that the warming to date and the rise in the CO2 concentration are linearly coupled, and then extrapolate into the future. 3. Projection of changes in climate: As just noted, while linear extrapolation might be an elementary way to get a sense of future warming, in the 1970s this led some to think the world would continue cooling rather than change over to a very significant warming since the 1970s. A major contributor to the cooling influence was, it appears (and seems reasonable), the buildup of sulfate aerosols, both due to growing emissions and to going to tall stacks for their emissions, which lengthened their atmospheric lifetime from a day or two to a week or two. At the time there were many (including the President’s Science Advisory Council in their 1965 report to President Lyndon Johnson), however, who realized that over time the buildup of greenhouse gases would come to dominate because of the very long (centennial to millennial) atmospheric lifetimes of the perturbations in concentration that were being caused. And that has been shown to be what has happened—understanding of the physics of an issue are a much more reliable approach to estimating future conditions than linear extrapolation. The climate models that have been developed incorporate all the many things that we have learned—they don’t let us just focus on one process or influence—we have to consider them all quantitatively and how they interact. To build confidence in the models, they are tested in many, many ways—not the exact situation, but as many different past cases and situations that we can. Indeed, there are still uncertainties due to limits to understanding (and some due to limitations in computer resources to allow fine enough spatial resolution in the models), but there is really no basis for selecting projections based on simple extrapolations compared to the much more comprehensive representations included in models. The Hadley Centre model results are among the most respected around the world. I just cannot accept your statement that the “science is highly uncertain”—we may not know exactly what the changes will be, but we have very strong reason to project warming of several degrees, and associated shifts in precipitation zones, etc. The representations of processes, including of water vapor, sea ice, and so on, are largely consistent with all that we have learned about climate system behavior—and that the climate sensitivity is very likely within the range 2-4°C, quite likely near the center of the range. Warming over the next few decades is likely to average a few tenths of a degree per decade. This is behind the equilibrium temperature increase associated with the particular CO2 concentration. Even if the world can stabilize the atmospheric CO2 concentration, this means that warming will continue for several decades more, and sea level rise will go on for centuries as the ocean slowly warms and as ice sheets deteriorate. And if the nations of the world cannot stabilize the atmospheric concentrations, the situation is likely to be much worse—polar warming could release a lot of methane or CO2, amplifying the warming influence; warming could accelerate ice sheet deterioration, increasing the rate of sea level rise to well over a meter per century (which was the average rate from about 20,000 to 8,000 years ago as the glacial ice sheets melted—and the warming during that period was much less rapid than the world is now undergoing), and more. In summary, there is compelling evidence that indicates that the extent and challenge of dealing with climate change is as serious as the IPCC has stated, and more likely is even more severe than less, given the potential tipping points and the cautious nature of the IPCC process that is necessary to generate the unanimous endorsements of the participating nations.

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