It’s Time to Explore Plan G: Only Geoengineering Has the Potential to Prevent Climate Change Disasters

by Thomas B. Stoel, Jr. © 2011

Table of Contents


I The Science of Climate Change

II The Political Situation

III The Challenge We Face Now

IV The Emissions Reduction Approach Has Inevitable Drawbacks

V If Possible, We Should Act to Cool the Earth Quickly

VI Geoengineering Research and Establishment of Governance Mechanisms Should Be an Urgent Priority

VII Next Steps


For those who aren’t familiar with the term “geogengineering,” we should start with a definition: Geoengineering consists of a large-scale human intervention in the Earth’s climate system in order to moderate global warming.

The basic message conveyed on this site is a simple one. Even if we do all we can to reduce emissions of greenhouse gases to slow global warming, scientists tell us that climate change disasters are inevitable. If we aren’t so successful in reducing emissions, or if nature reacts to warming in truly catastrophic ways, the outcome could be much worse. It appears that the only way of preventing disasters due to global warming is to use geoengineering to cool the earth in the relatively near future. If geoengineering is to be an available option, we must act very soon to increase our research into its likely environmental impacts and to negotiate a global treaty that legitimizes its use.

There is a strong scientific consensus that global warming is occurring, that it is largely driven by greenhouse gas emissions due to human activity, and that it will have disastrous impacts unless actions are taken to limit it. That view is shared by the overwhelming majority of the world’s qualified climate scientists. It is based both on theoretical models and on thousands of real-world observations of the effects of climate change, including effects that are apparent in our own lives or in readily available images, such as the earlier arrival of the spring season, the worldwide retreat of glaciers, and the diminished extent of Arctic sea ice in summer.

Scientists are warning that disastrous consequences of global warming – such as droughts, floods, heat waves, and more intense typhoons and hurricanes — will intensify as the Earth continues to warm, and that there is no natural stopping point to the warming process so long as greenhouse gas emissions continue at anything like the present rate. To prevent climate-driven catastrophes by reducing greenhouse gas emissions will require a very rapid revolution in energy production and consumption in both industrialized and developing countries, based on a global regime featuring goals, timetables, and financial assistance from rich nations to poor ones.

The disappointing outcome of the December 2009 international conference in Copenhagen, Denmark, a conference that had been expected to set the stage for a treaty requiring the world’s nations to limit sharply their emissions of greenhouse gases, revealed how difficult it will be to institute such a global regime. The task has been made more difficult because efforts to enact legislation establishing a U.S. emissions reduction regime collapsed this past summer. Moreover, if we’re able to establish an international regime in the next few years, it may not be implemented on schedule, because of missteps due to national rivalries and economic and technological uncertainties. In the meantime, the gases that cause global warming will continue to accumulate in the atmosphere.

Even if we assume that all of these obstacles can be overcome and greenhouse gas emissions reduced by the amounts suggested by scientists, global warming is still likely to have disastrous impacts. Scientists remain uncertain about key elements of the global warming problem, such as the likely rate of sea-level rise and “positive feedback” effects — such as large-scale releases of methane from melting Arctic tundra — that could cause greater-than-predicted warming. So the consequences of warming could be greater than scientists currently expect. That’s what has happened with respect to past scientific predictions, such as those concerning the melting of Arctic sea ice.

Even if we’re lucky with regard to these uncertainties, scientists tell us that global warming is bound to have effects that can properly be termed disastrous. These include:

  • The extinction of one-sixth or more of all the terrestrialspecies on earth.
  • Catastrophic impacts on marine species and habitats.
  • Major losses in food production.
  • Droughts that will cause horrendous wildfires and loss of human life.
  • Severe shortages of fresh water.
  • Calamities in poor nations due to sea-level rise and more intense hurricanes.

Moreover, the global warming that is bound to occur in the future even under an effective emission reduction regime will essentially be irreversible. Even if all human-caused emissions of carbon dioxide, the main greenhouse gas, were to stop right now, global temperatures wouldn’t decline for centuries.

These considerations suggest that, in addition to reducing greenhouse gas emissions as fast as possible, we should act to stabilize or decrease the earth’s temperature in the relatively near future, if it’s possible to do so without unacceptable adverse impacts. This does not imply that the world community should relax its efforts to reduce greenhouse gas emissions. The higher the level of greenhouse gases in the atmosphere, the worse will be the ensuing catastrophes. We must do our utmost to reduce greenhouse gas emissions.

There have been discussions of various methods of cooling our planet at an affordable cost. It appears that the most effectivetechnique would be to inject sulfate aerosols into the atmosphere, in order to reflect sunlight and cool the Earthin a manner similarto the way particles emitted during volcanic eruptions are known to block sunlight and lower the Earth’s temperature. This apparently could be done in the very near future at a relatively low cost. The key question is whether this kind of geoengineering would have unacceptable environmental impacts.

Some discussions of geoengineering appear to assume that we can afford to explore the option in a leisurely fashion, an assumption reflected in the frequent descriptions of geoengineering as a “method of last resort.” There are two problems with this mindset. First, it overlooks the severe harm from climate change that is predicted to occur or become inevitable within a few decades, or even a few years, unless the warming trend is reversed. Second, it supposes that we will learn that the Earth is approaching a tipping point that would trigger a “doomsday effect” or “climatic disaster” — like shutting down the Gulf Stream or a gigantic release of methane from permafrost — while there is still time to employ the geoengineering option. But that assumption ignores the very realpossibility that we will discover that we are near a tipping point only after we have passed the point of no return and disaster has become inevitable.

It follows that there is an urgent, near-term need to make the geoengineering option a real possibility. Yet scientific research on geoengineering and its effects is now being carried out on a tiny scale by a relatively few scientists, with very little governmental funding. The United States should move quickly to establish a strong, comprehensive, well-funded research program, and to persuade other nations to do the same.

The effects of a large-scale geoengineering experiment will be felt globally, or at least over a large part of our planet. Full-scale use of geoengineering to reduce the Earth’s temperature would affect all of humanity. Considerations of fairness dictate that such an effort should take place only with the informed consent of those who might be affected. It follows that there must be an internationally agreed decisionmaking process that ensures that kind of informed consent. Legal and politicalthinkers from many parts of the world should begin as soon as possible to lay the groundwork for an international treaty that creates such a process.

I The Science of Climate Change

The IntergovernmentalPanel on Climate Change (IPCC) is a broad-based, international scientific body that was established by governments in 1988 to review and assess scientific findings concerning climate change, and provide updated information to decisionmakers.  The IPCC issues periodically an “assessment report” that includes a summary for policymakers. The most recent report, issued in 2007, reflected the work of more than 2500 experts from 130 countries, who served as authors and reviewers.

The IPCC’s 2007 Assessment Report states that there is an overwhelming scientific consensus that global warming is occurring, that it is largely driven by greenhouse gas emissions due to human activity, and that warming is likely to have severe adverse effects. (IPCC, Fourth Assessment Report, Summary for Policymakers, The IPCC concluded that those adverse effects can be mitigated, though not entirely prevented, by altering human activities so as to reduce greenhouse gas emissions.

The IPCC’s2007 Report cites both climate models and many types of observationalevidence to support its conclusion that “[w]arming of the climate system is unequivocal” (see the Summary for Policymakers cited in the last paragraph). The observational evidence includes:

  • Data showing that 11 of the preceding 12 years ranked among the 12 warmest in the record of global surface temperatures since 1850, and evidence that average Northern Hemisphere temperatures during the second half of the 20th century were “very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years.”
  • Measurements showing a significant rise in the global average sea level since 1961.
  • Satellite data since 1978 showing large decreases in the extent of Arctic sea ice, especially in summer.
  • Measured declines in the extent of mountain glaciers and snow cover in bothhemispheres of the Earth.
  • Evidence showing a likely increase in the area of the globe affected by drought.
  • Evidence showing a strong likelihood that over the past 50 years “cold nights and frosts have become less frequent over most land areas, and hot days and hot nights have become more frequent.”
  • Evidence showing a likelihood that heat waves have become more frequent over most land areas.
  • Evidence showing a likelihood that “heavy precipitation events” have increased over most areas.
  • Observational evidence of an increase in intense tropical cyclone activity in the North Atlantic since about 1970, and some evidence of increases elsewhere.
  • Strong evidence of earlier timing of spring events and poleward and upward shifts in plant and animal ranges in terrestrial ecosystems (i.e., animal and plant species are migrating toward the poles and to higher altitudes, when that is possible).
  • Strong evidence in some marine and freshwater systems of temperature-related changes in algal, plankton and fish abundance, as well as changes in ice cover, salinity, oxygen levels and circulation.

These findings have been corroborated by many other scientific authorities. For example, NASA’s website on Key Indicators of Global Climate provides updated evidence that: (1) globalsurface temperatures are rising, and the period from January 2000 to December 2009 was the warmest decade on record; (2) sea levels are continuing to rise; (3) September Arctic sea ice is declining at a rate of 11.2% per decade (September is the monthwhen the ice reaches its minimum extent); (4) the land ice sheets in both Antarctica and Greenland are losing mass. (See

Some people continue to express doubts about the IPCC’s conclusion that global warming is due in large part to human activities, a view that is shared by almost all scientists who are qualified to make a judgment. Skeptics should keep in mind that:

  1. The greenhouse effect — in which solar radiation strikes the earth and is reflected back toward space in the form of heat (infrared radiation), and that heat is absorbed by “greenhouse gases” in the earth’s atmosphere, thereby warming the atmosphere — is a proven reality. Without the greenhouse effect, the earth would be about 60 degrees Fahrenheit colder than it is now.
  2. Greenhouse gas emissions due to human burning of fossil fuels have increased substantially the concentrations of greenhouse gases in the atmosphere. For example, the concentration of carbon dioxide, the main greenhouse gas, has risen from its pre-industrial level of 280 parts per million to about 390 ppm, and is rising by about 0.4% per year.
  3. Since greenhouse gases cause global warming, it is to be expected that a denser layer of greenhouse gases around the earth would add to that warming. The burden is on the skeptics to show that a “negative feedback” effect, such as a change in the amount of cloud cover, is operating to prevent additional warming. The scientific consensus is that they haven’t done so.

In May 2010, the U.S. National Research Council, the institution that is charged by Congress with providing science, technology and health policy advice to the U.S. Government, responded to a congressional mandate to “investigate and study the serious and sweeping issues relating to global climate change” by issuing a report entitled “Advancing the Science of Climate Change.” (see The Report’s Summary begins with an unequivocal conclusion:

Climate change is occurring, is caused largely by human activities, and poses significant risks for—and in many cases is already affecting—a broad range of human and natural systems.

This conclusion is based on a substantial array of scientific evidence, including recent work, and is consistent with the conclusions of recent assessments by the U.S. Global Change Research Program (USGCRP, 2009a, and others), the Intergovernmental Panel on Climate Change’s Fourth Assessment Report (IPCC, 2007a-d), and other assessments of the state of scientific knowledge on climate change.

II The Political Situation

Because the IPCC is a scientific rather than a political body, the IPCC’s reports haven’t identified a specific goal for limiting the increase in global temperature. However, in view of the IPCC’s findings, there is a growing consensus among scientists and politicalleaders that a temperature increase of more than 2.0-2.4 degrees Centigrade above pre-industrial levels would pose unacceptable risks.

Some highly qualified scientists have dissented from the two-degrees-Centigrade goal because they find it too modest. For example, one renowned climate researcher, Dr. James Hansen of NASA, said in 2008:

[T]he disturbing conclusion, documented in a paper I have written with several of the world’s leading climate experts, is that the safe level of atmospheric carbon dioxide is no more than 350 ppm (parts per million) and it may be less. Carbon dioxide amount is already 385 ppm and rising about 2 ppm per year. Stunning corollary: the oft-stated goal to keep global warming less than two degrees Celsius (3.6 degrees Fahrenheit) is a recipe for global disaster, not salvation. (

The IPCC Working Group that focused on mitigation found in 2007 that to limit the temperature increase to two degrees C, global emissions of carbon dioxide, the major greenhouse gas, would have to peak by about 2020 and decline 50-85% by the year 2050, as compared with the level in the year 2000. (IPCC Working Group III, Summary for Policymakers, Table SPM 5 ( Achievement of these goals would require heroic efforts both by industrialized nations, which now account for about 55% of global greenhouse gas emissions, and by developing countries, which emit the remaining 45% (about 40% of developing-country CO2 emissions result from burning of forests). Simple arithmetic tells us that if the industrialized nations are able to reduce their emissions by 80% between now and 2050, the developing countries must reduce theirs by about 10% in order to reduce global emissions by 50%.

A second May 2010 report by the U.S. National Research Council, “Limiting the Magnitude of Future Climate Change,” reaches broadly similar conclusions. It focuses on the desirability of reducing U.S. greenhouse gas emissions by 50-80% below 1990 levels by the year 2050. (See The “Report Brief” recommends that the United States:

[adopt a] policy goal stated in terms of a budget for cumulative greenhouse gas emissions over the period 2012-2050. With only so much to “spend” during this period, the nation should act now to: (1) take advantage of key near-term opportunities to limit greenhouse gas emissions (e.g., through energy efficiency and low carbon energy sources), and to create new and better emission reduction opportunities for the longer term (e.g., invest in research and development); (2) create a national policy framework within which actors at all levels can work toward a common goal; and (3) develop policy mechanisms durable enough to persist for decades but flexible enough to adapt to new information and understanding.

Outside the United States, some political leaders already have taken strong action in response to scientific findings. In 1996, the European Union heeded early warnings from the IPCC and adopted the goal of limiting the rise in average global temperature to two degrees C. In 2007, the EU — which by then comprised 27 member nations with a total gross domestic product of more than $15 trillion and a combined population of nearly 500 million – agreed to reduce community-wide greenhouse gas emissions by 20% below 1990 levels by the year 2020 in order to meet that target. EU nations are negotiating an action plan to achieve the required reduction in emissions, including specific emission goals for each member nation.

At the global level, since 1998 about 175 nations have ratified the Kyoto Protocol to the international Framework Convention on Climate Change. Industrialized nations that became parties to the Protocol pledged that they would reduce greenhouse gas emissions by specified amounts by the year 2012. The goal is for the average reduction by all industrialized nations to equal 5% as compared with 1990 emissions.

In the fall of 2007, the EU reported that the “EU-15″ nations — the 15 countries that were members of the European Union in 2004 and account more than 10% of global greenhouse gas emissions — were on track to reach their Kyoto Protocol emissions target, an 8%
reduction below 1990 levels by the year 2012. Between 1990 and 2005, the EU-15 succeeded in reducing their total emissions by 2%.

This was encouraging news. However, there are sobering elements even in this success story. Eight of the EU-15 nations lessened their emissions between 1990 and 2005, the last year for which data are available. But 90% of the emissions reductions achieved by those nations came from just two countries: Germany and the United Kingdom. Germany and the UK achieved those reductions mainly by switching from coal to natural gas, a fuel that emits less greenhouse gases (as well as less conventional air pollutants) when it is burned. That one-time gain probably would have occurred anyway, in order to reduce air pollution. It can’t be replicated.

There has been no such success in the United States, which until recently was the biggest emitter of greenhouse gases. The EPA’s ”2010 U.S. Greenhouse Gas Inventory Report” found that “total U.S. emissions have risen by almost 14 percent from 1990 to 2008.”  ( The United States hasn’t ratified the Kyoto Protocol, and as of now is subject to no limit on its emissions. The Obama Administration has pledged to reduce U.S. emissions 17% by the year 2020, as compared with emissions in the year 2005, but it’s far from certain that we will meet that goal.

Developing nations that became parties to the Kyoto Protocol weren’t required to reduce their emissions. Most of them continue to resist the adoption of legally binding limits, citing the overriding need to increase the economic welfare of their citizens from its current low level. They point out both that Western nations have accounted for the great bulk of past greenhouse gas emissions, and therefore are responsible for most of the global warming that has occurred to date, and that per capita emissions from developing nations are much lower than in industrialized countries.

Yet the emissions growth that is projected to occur in developing countries seems certain to push the earth above the two-degree-Centigrade limit unless those nations act to control their emissions. China has overtaken the United States as the largest emitter of greenhouse gases, and India is thought to be the fifth biggest emitter. In recent years, China and India have been among the world’s fastest-growing economies, and in coming decades they are expected to account for a huge proportion of the worldwide growth in coal-fired power plants and motor vehicle use.

In the absence of limits, increased emissions from these two nations, which have a combined population of 2.4 billion people and currently account for more than 20% of worldwide emissions, could offset most of the emissions reductions achieved by industrialized countries, even if the latter make heroic efforts. Other developing nations including economic powerhouses like Brazil and Mexico, as well as rapidly deforesting Indonesia, also account for a significant share of world emissions. Their emissions are growing relatively fast and must be controlled if the earth is to remain within temperature limits.

Against this background, much was expected from the December 2009 Copenhagen conference of the parties to the Kyoto Protocol, which is scheduled to expire in 2012. Many people expected that the conference would set the stage for a new global treaty that requires all significant emitters of greenhouse gases to reduce their emissions by agreed amounts.

The Copenhagen meeting ended without any such agreement, due to major disagreements between developing and industrialized nations. Only a last-minute intervention by President Obama resulted in a final text: the “Copenhagen Accord.” ( However, the nations assembled at Copenhagen agreed only to “take note” of the Accord rather than to be legally bound by it.

The first paragraph of the Accord acknowledges the goal of holding the eventual global increase in temperature to 2 degrees C. The second paragraph states:

We agree that deep cuts in global emissions are required according to science, and as documented by the IPCC Fourth Assessment Report with a view to reduce global emissions so as to hold the increase in global temperature below 2 degrees Celsius, and take action to meet this objective consistent with science and on the basis of equity. We should cooperate in achieving the peaking of global and national emissions as soon as possible, recognizing that the time frame for peaking will be longer in developing countries and bearing in mind that social and economic development and poverty eradication are the first and overriding priorities of developing countries and that a low-emission development strategy is indispensable to sustainable development.

Unfortunately, these aspirational statements weren’t accompanied by any legally binding requirements. Instead, the Accord was described only as “politically binding” on the countries that chose to sign it. Moreover, the Accord contains no requirement that nations reduce emissions beyond the levels already agreed to by some industrialized countries. Instead, it says that all nations except the least developed are to set their own national goals and report them to the Kyoto Protocol’s secretariat. The Accord doesn’t even set forth any numerical emission goals (according to the December 30, 2009, issue of the Economist, a Swedish delegate explained this omission by saying “China don’t like numbers”), and it says nothing about further efforts to develop internationally binding emission limits. The Accord did make some gains with respect to verification of actions to achieve emission-reduction goals established by countries, efforts to reduce deforestation, and resource transfers from industrialized to developing nations. However, because of its deficiencies, the overall effect of the Accord in limiting emissions remains highly uncertain.

Thus the result of the Copenhagen meeting fell far short of the kind of agreement that would be necessary to hold the increase in the earth’s temperature below two degrees C. The conference was widely described as a failure. Thoughtful environmental activist Bill McKibben called it a “train wreck.” ( The Financial Times said the meeting produced “the emptiest deal one could imagine, short of a fist fight” (editorial, Dec. 20, 2009). Some observers played the “blame game,” pointing their fingers at alleged villains including the United States, China, host country Denmark, and various developing nations.

As part of the “pledging” process that followed the Copenhagen meeting, China stated that it aims by 2020 to reduce its “carbon intensity” — the carbon emissions associated with each unit of economic gain — by 40-45%, compared with 2005 levels. India pledged a corresponding 20-25% reduction in intensity, and Brazil committed to reduce its greenhouse gas emissions by nearly 40% below the levels projected for 2020. However, the bottom-line reductions in emissions remain uncertain, since none of these pledges, with the possible exception of Brazil’s, includes an absolute emissions target. And these goals are only aspirational, not internationally binding.

The same nations met again in Cancun, Mexico, from November 29 to December 10, 2010, to engage in climate change negotiations. The resulting “Cancun Agreements” reaffirmed the commitment of the world community to hold the eventual rise in global temperature to two degrees Centigrade. The Agreements fleshed out important elements that were identified in the Copenhagen Accord, including establishment of a “Green Climate Fund” that will provide financial assistance to enable poor countries to adapt to climate change and develop green technologies; monitoring mechanisms — including an independent panel of experts — to ensure that nations fulfill their pledges to reduce greenhouse gas emissions; and an international system for reducing emissions from deforestation and forest degradation, including transfers of funds from rich countries to poor ones.

The Cancun meeting revived a spirit of international cooperation that had was largely absent at Copenhagen and reestablished the United Nations as a credible forum for climate change negotiations. Yet, as explained in Part III below, experts think it’s extremely unlikely that we can reduce greenhouse gas emissions enough to remain within the two-degree-Centigrade limit unless nations — including all the major emitters of greenhouse gases — agree to binding limits on their emissions. The Cancun meeting didn’t address this issue directly, and most of the current limits on emissions by industrialized nations will disappear when the Kyoto Protocol expires in 2012 (the nations of the European Community have agreed to achieve longer-term emission reductions).

Unfortunately, other developments during 2010 have reduced the odds of achieving the required post-Kyoto agreements. With respect to the United States, the US House of Representatives is now controlled by Republicans, many of whom actually deny the reality of human-caused climate change; the ranks of deniers in the Senate have increased; and polls show a drop in the percentage of Americans who believe their country should act against climate change. Against this backdrop, any pledge by the United States to achieve long-term emission reduction goals will lack credibility, and there is little chance that the Senate will ratify a successor agreement to the Kyoto Protocol (which the United States has never ratified) or any other treaty establishing binding limits on US emissions. In addition, Japan and Russia both announced during the Cancun talks that they would not sign a successor treaty to the Kyoto Protocol, and Canada also was reported to oppose extension of the Protocol. (The Guardian, Dec. 10, 2010,

Global greenhouse gas emissions are on a growth trajectory that soon will make it impossible to limit the eventual rise in the Earth’s temperature to two degrees Centigrade. It’s hard to exaggerate how severe the consequences may be if emissions continue along that path. Altering the earth’s climate so much that it falls outside the limits experienced by any human civilization amounts to an enormous gamble, with no fallback position if the gamble doesn’t succeed. Hurricane Katrina, record-setting heat waves in many parts of the world, widespread droughts, and disastrous wildfires like the recent ones in Southern California, Australia, and Russia are just a taste of what may be in store. The unforeseen rapidity of ice melting in the Arctic and Antarctic, which could result in catastrophic sea-level rise, suggests that even greater calamities may await us.

Moreover, one hard truth about global warming is that there appears to be no natural stopping point. Unless the world community takes strong actions, continued greenhouse gas emissions will cause temperatures to climb indefinitely. It’s possible, perhaps even likely, that the rate of increase will accelerate due to positive feedback effects like the release of methane from the decay of vegetation that is now sequestered in Arctic permafrost, less reflection of incoming solar radiation back into space as Arctic sea ice disappears, and reduced absorption of carbon dioxide by the oceans as ocean waters become saturated with CO2. It’s sobering to contemplate our planetary neighbor, Venus, where global warming has contributed to surface temperatures of more than 700 degrees Fahrenheit.

A second hard truth is that it’s not only the ultimate amount of global warming that matters: the rate of warming is also important. One reason is that the ability of key ecosystems to adapt to higher temperatures depends on the rate at which temperatures change. For example, forests will be greatly affected as temperatures become too high for particular tree species to grow in an area. Yet forests have limited ability to “migrate” toward the earth’s poles in search of lower temperatures. If the temperature rises too fast, that limit will be exceeded and forest types may disappear instead of changing location. The same is true of many marine species and ecosystems.

There are huge obstacles to achieving the emission reductions necessary to limit the eventual global temperature increase to two degrees C, much less the more stringent limits proposed by James Hansen and others. Fossil fuels, the greatest source of greenhouse gases, currently account for about 85% of US energy use and about the same proportion of marketed world energy consumption (excluding energy sources like locally collected wood). To reduce its fossil fuel use by 80%, the United States will have to increase its reliance on non-fossil energy from about 15% of total consumption to the great majority in just a few decades. Europe, Japan, and other industrialized economies face a similar challenge. For developing nations to reduce their emissions by the required amounts, they will have to satisfy from non-fossil sources most of the huge increase in energy services which will be needed if they are to grow at anything like present rates. Developing countries are unlikely to settle for slower growth, since that would compel more of their people to remain in a state of poverty that is unimaginable to most Americans and Europeans.

The last paragraph, like most analyses, focuses on reducing emissions of carbon dioxide, which account for about 80% of the contribution to global warming of all greenhouse gas emissions. However, there are other significant greenhouse gases, notably the “trace gases” methane, nitrous oxide, and chlorofluorocarbons (CFCs).  Per molecule, these gases absorb infrared radiation and heat the atmosphere much more strongly than carbon dioxide. CFC emissions are strongly regulated to protect the stratospheric ozone layer. Various efforts are underway to reduce emissions of methane and nitrous oxide, and additional actions have been proposed (see, e.g.,;; and “Methane Blue Ribbon Panel: A Fast-Action Plan for Immediate Methane Abatement,”

The foregoing makes it clear that limiting the global temperature increase to only two degrees Centigrade would require mammoth, sustained, coordinated actions on a global scale over a period of decades. The only remotely comparable effort in human history may be the cooperation of the Allies during World War II. Some expert analyses have suggested that even with a maximum effort, the task may be impossible. The International Energy Agency found in 2006 that a heroic global effort using all available technologies could only stabilize global emissions at present levels by 2050, far from the goal of reducing emissions by 50-80%. (IEA, Energy Technology Perspectives 2006 — Scenarios & Strategies to 2050; Princeton University scientists Robert Socolow and Stephen Pacalareached a similar conclusion in a July 2006 Scientific American article entitled “A Plan to Keep Carbon in Check.” ( They declared: “To hold global emissions constant while the world’s economy continues to grow is a daunting task.”

Another useful analysis is that in Stern Review: The Economics of Climate Change. (see This extensive review, commissioned by the British Government and led by British economist Nicholas Stern, concluded in 2006 that the benefits of strong actions to reduce greenhouse gas emissions greatly outweigh the costs:

[I]f we don’t act, the overall costs and risks of climate change will be equivalent to losing at least 5% of global GDP each year, now and forever. If a wider range of risks and impacts is taken into account, the estimates of damage could rise to 20% of GDP or more. . . . In contrast, the costs of action – reducing greenhouse gas emissions to avoid the worst impacts of climate change – can be limited to around 1% of global GDP each year. . . . The investment that takes place in the next 10-20 years will have a profound effect on the climate in the second half of this century and in the next. Our actions now and over the coming decades could create risks of major disruption to economic and social activity, on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century. And it will be difficult or impossible to reverse these changes. . . . .

Climate change is the greatest market failure the world has ever seen, and it interacts with other market imperfections. Three elements of policy are required for an effective global response. The first is the pricing of carbon, implemented through tax, trading or regulation. The second is policy to support innovation and the deployment of low-carbon technologies. And the third is action to remove barriers to energy efficiency, and to inform, educate and persuade individuals about what they can do to respond to climate change. (Stern Review, Summary of Conclusions.)

As noted in the Stern Review, success in reducing emissions will depend on wide, rapid deployment of new, cost-effective energy technologies. Yet highly touted approaches often resemble mirages, as their promise recedes into the future. For decades, people have hoped that solar energy will soon become as cheap as energy from fossil fuels. That may happen, but no one thinks the day is at hand. Another tantalizing prospect is to make coal — the most carbon-intensive fossil fuel — harmless by sequestering its carbon-laden effluent in places where it can’t reach the atmosphere. R&D efforts are underway in the United States and abroad, but it’s clear that sequestration of carbon on a large scale won’t begin soon. (See US Department of Energy, “Carbon Sequestration,” at

As the Stern Review also points out, it’s hard to see how emission reduction goals can be reached without a mechanism that rewards low-carbon energy production and penalizes “dirty” methods, because fossil-fuel energy currently has a significant cost advantage over low-carbon energy sources. Yet only the EU and some of its members have put in place a “cap-and-trade” regime that does this (another approach would be to impose a tax on carbon emissions). It will be difficult for the EU act strongly enough, or for others to follow its example, in the absence of a global system that prevents carbon-intensive economies from gaining a competitive advantage.

In short, the world has scarcely begun to address the enormous challenge of preventing catastrophes due to climate change. The disappointing outcome of the Copenhagen meeting shows how far we are from the sort of international cooperation that is needed. At present, there is no binding global emissions cap or tax that favors low-carbon energy production, and no plan to develop them. Only the European Union has embarked on an energy path that would achieve the global goal set forth at Copenhagen. The outlook for achieving the U.S. emissions reduction goal endorsed by the Obama Administration is highly uncertain, especially since the Congress has refused to pass a “cap and trade” bill (the Environmental Protection Agency does have power to regulate greenhouse gas emissions). Even if the goal is achieved, the United States will by 2020 reduce emissions by only 4% as compared with 1990 levels, far short of the EU’s target of a 20% reduction.

IV The Emissions Reduction Approach Has Inevitable Drawbacks

We have seen that the obstacles to an effective global emission reduction regime are formidable. But let’s wave a magic wand and assume that we soon will live in a world where all nations are taking steps designed to reduce global greenhouse gas emissions 50% by the year 2050. Unfortunately, there still would be good reasons to fear catastrophic consequences from global warming.

Reason # 1: Scientific uncertainties. Up to now, the effects of global warming have mainly proven to be more severe than scientists had foreseen, due to the fact that there are major uncertainties about the climate system and the relationship between that system and the biosphere, and that scientists tend to be cautious in the face of uncertainty (see, e.g., James Hansen, “Scientific reticence and sea level rise,” Eviron. Res. Lett., vol. 2, no. 2 (2007)). There are numerous examples:

  • The rapid warming and sea-ice melt that is now being observed in the polar regions wasn’t foreseen by most scientists. The impending disappearance of Arctic summer sea ice surely will be considered a disaster by those who care about polar bears, walruses, and other elements of the Arctic ecosystem. And rapid warming of Arctic permafrost may cause very large releases of methane from previously frozen tundra.
  • There are ominous signs that the massive ice sheets of Greenland and Antarctica are melting much faster than predicted. Their loss could cause sea levels to rise on the order of 20 feet in as little as a century (see J. Hansen, “Huge sea level rises are coming – unless we act now,” New Scientist, 25 July 2007). On this crucially important question, the IPCC’s 2007 report says only: “There is better understanding than in [our 2001 report] that the risk of additionalcontributions to sea level rise from both the Greenland and possibly Antarctic ice sheets may be larger than projected by ice sheet models and could occur on century time scales. This is because ice dynamical processes seen in recent observations but not fully included in ice sheet models assessed in [this report] could increase the rate of ice loss.” (IPCC, Climate Change 2007: Synthesis Report, Summary for Policymakers, p. 19)
  • Another major impact of CO2 buildup in the atmosphere – the threat to marine life from acidification of the oceans — wasn’t recognized until recently and isn’t well understood. Ecologist Thomas Lovejoy said in 2008: “It’s the most profound environmental change I’ve seen in my entire career, and nobody saw it coming.” Researchers believe that continued acidification could largely eliminate coral reefs and damage other important marine ecosystems on a worldwide basis. The IPCC noted that acidification is occurring, but stated that “the effects of observed ocean acidification on the marine biosphere are as yet undocumented.” (IPCC, Climate Change 2007: Synthesis Report, Summary for Policymakers, p. 9)
  • Greenhouse gas emissions may trigger “positive feedback” effects that will lead to further warming. For example: (1) disappearance of Arctic sea ice will reduce the amount of solar radiation that is reflected back into space and thereby increase warming; (2) warming that is already inevitable may cause the release of methane, a potent greenhouse gas, from previously frozen Arctic vegetation, and thereby increase warming; (3) the ability of the oceans, which currently soak up about half of the carbon dioxide that is emitted into the atmosphere, may decline as they become more saturated with CO2, resulting in increased atmospheric concentrations of CO2 that will cause additional warming.
  • Other disasters are probable. Renowned climatologist Wallace Broecker has warned for many years about the likelihood of “unpleasant surprises in the greenhouse,” including possible catastrophes such as the “shutting down” of the Gulf Stream that warms the North Atlantic. It’s impossible to be specific about unexpected events. But the earth’s atmospheric and biological systems are complex and by no means fully understood. And a recent University of California study found that “[climate] regime shifts with potentially large consequences can happen without warning — systems can ‘tip’ precipitously.” (“Climate ‘Tipping Points’ May Arrive Without Warning, Says Top Forecaster,” Science Daily, Feb. 10, 2010)

Reason # 2: Significantly higher temperatures seem inevitable and will have catastrophic effects. Even under the most stringent emissions reduction regime that is being considered by policymakers, scientists predict that globaltemperatures will continue to rise well into the 22d century, and that the eventualincrease will be at least two degrees Centigrade above pre-industrial levels. The consequences for the world’s human, biological, and geophysical systems under this scenario can properly be termed catastrophic. They include:

  • The likely extinction of one-sixth or more of all the terrestrial species on earth by the year 2050. A 2004 study published in the prestigious scientific journal Nature concluded that “anthropogenic climate warming . . . is likely to be the greatest threat [to globalbiodiversity] in many if not most regions” and that “[m]inimum expected (that is, inevitable) climate-change scenarios for 2050″ will drive18% of terrestrial species to extinction. (C. Thomas, et al., “Extinction risk from climate change,” Nature, vol. 427, p. 145 (8 Jan. 2004))
  • Enormous adverse impacts on marine ecosystems and species. Global warming is adding substantially to the pressures that are driving many marine species to extinction, especially in species-rich coral reef ecosystems, and is damaging other marine systems — including coastal habitats threatened by sea-level rise — on which millions of people rely for food and economic welfare. Moreover, recent research suggests that global warming is a major cause of the substantial recent decline in marine phytoplankton, tiny marine organisms that account for half of all photosynthetic activity on earth and therefore absorb huge amounts of carbon dioxide. (D. Boyce, et al., “Global phytoplankton decline over the past century,” Nature, vol. 466, pp. 591-596 (29 July 2010))
  • Changes in natural systems short of extinction that will impose huge natural, economic, and social costs. To cite just one example, global-warming-induced infestations of Canadian and U.S. forests by the mountain pine beetle have destroyed tens of thousands of square miles of forests and imposed economic losses totaling tens of billions of dollars. (See, e.g., G. Hamilton, “Pine beetle moves south in B.C.,” Vancouver Sun, Sept. 18, 2007). In addition, the dead forests have changed from a small net carbon sink to a large net carbon source, a positive feedback effect that will cause more global warming.
  • Loss of food production and increased wildfires due to severe droughts and heat waves. The IPCC says that global warming probably has contributed to recent droughts and is likely to result in more droughts in the future. The Australian drought that began in 2003 was the worst in Australia’s history; contributed to a spike in world food prices; and led to horrific wildfires in the Australian state of Victoria that killed some 200 people in 2009. In 2008, drought-induced fires in California caused more than $1 billion in damage. A Russian heat wave and drought in the summer of 2010 set temperature records; contributed to widespread wildfires; caused an estimated 15,000 deaths and $15 billion in economic costs; and forced Russia to ban grain exports until the end of 2010.
  • Shortages of fresh water due to the disappearance of glaciers and reduction of mountain snow packs. As global populations rise and economies grow, fresh water will be an increasingly precious resource. The effects of water shortages will be severe in US regions like Southern California. In developing countries, including those near the Andean and Himalayan mountain ranges, they will cause widespread suffering and hamper efforts to pull hundreds of millions of people out of poverty.
  • Sea-level rise along the coasts of poor nations that constitutes a slow-moving catastrophe. A 2007 analysis by the World Bank concluded that “even a one meter rise would turn at least 56 million people in the developing world into environmental refugees.” Severely affected countries would include Vietnam, where 11% percent of the nation’s population would be displaced; Egypt’s Nile Delta, with more than 10% percent of the population at risk and 25% of the delta flooded; and Bangladesh, where a densely concentrated population of more than 200 million would be forced into an even smaller land area. (World Bank summary of a 2007 working paper entitled “The impact of sea level rise on developing countries: a comparative analysis.”)
  • Disasters due to the increased intensity of tropical cyclones (which Americans call hurricanes). The IPCC report says only that “Regional scale changes [due to global warming] include . . . likely increase in tropical cyclone activity.” This seems like a modest statement, but such an increase could have horrific consequences, as illustrated by the May 2008 cyclone that killed more than 100,000 people in low-lying parts of Myanmar and the economic and human damage inflicted by Hurricane Katrina.

Non-scientists sometimes assume that large reductions in greenhouse gas emissions not only will limit the future increase in global temperatures but will cool the atmosphere in a relatively short time, so that temperatures will return to current or even pre-industrial levels. Unfortunately, that’s not the case. Even if all human-caused emissions of carbon dioxide, the main greenhouse gas, were to cease immediately, global temperatures wouldn’t decline for centuries. (See Susan Solomon, “Irreversible climate change due to carbon dioxide emissions,” Proceedings of the National Academy of Sciences, Jan. 2009.) The reason is simple. The intensity of the greenhouse effect depends on the atmospheric concentration of greenhouse gases. Reducing human-caused emissions only lessens the rate at which that concentration increases or, at best, prevents it from increasing further. The oft-cited analogy is to a bathtub in which human-caused emissions are represented by the water flowing in through the tap; reducing or even shutting off the flow does nothing to reduce the water level in the bathtub. Diminishing the atmospheric concentration of CO2 and lowering the temperature will depend on the slow absorption of CO2 by natural systems, most notably the world’s oceans, which have a circulation timescale of millennia.

V If Possible, We Should Act To Cool the Earth Quickly

The foregoing demonstrates that it will be extremely difficult to limit the increase in atmospheric temperature to two degrees Centigrade, and that even if we succeed in doing so over the next 40 years, we won’t be able to prevent catastrophic consequences. This does not imply that the world community should relax its efforts to reduce greenhouse gas emissions. The higher the level of greenhouse gases in the atmosphere, the worse will be the ensuing catastrophes. We must do our utmost to reduce greenhouse gas emissions.

However, the substantial chance that we won’t succeed in meeting our emission reduction goals, and the likelihood of catastrophic impacts from global warming even if we do succeed, suggest that in addition to reducing emissions we should act to lower globaltemperatures relatively quickly, something that emission reductions cannot accomplish. If that effort is successful, we will avoid many of the catastrophes listed above, with the major exception of acidification of the oceans. A number of ways have been suggested by which we might intervene to modify the earth’s climate system in order to moderate or reverse global warming. These methods have come to be known as “geoengineering.”

Possible Geoengineering Methods

The best discussion of geoengineering from the perspectiveof the natural sciences and engineering is contained in a September 2009 report by Britain’s Royal Society entitled “Geoengineering the climate: science, governance and uncertainty” (hereafter cited as “RS Report”), which can be found at The Royal Society Report focuses on carbon dioxide, the main greenhouse gas. It divides geoengineeringmethods into two categories: (1) “carbon dioxide removal” techniques that remove greenhouse gases from the atmosphere; and (2) “solar radiation management” (SRM) techniques that offsetthe impacts of increased greenhouse gas concentrations by causing the Earth to absorb less solar radiation.

In the first category, the Royal Society Report discusses six methods for removing carbon dioxide from the atmosphere (RS Report, pp. 9-21):

  • Changes in forestry and land use practices to maximize CO2 absorption by vegetation and soils.
  • Using biomass as a “carbon neutral” energy source or sequestering CO2 in biomass (e.g., in the form of charcoal).
  • Enhancing natural weathering processes, either on land or in the oceans, to remove CO2 from the atmosphere.
  • Using various methods to capture CO2 from the air, as is now done by some commercial systems.
  • Enhancing ocean uptake of CO2 by methods such as fertilizing the oceans with naturally scarce nutrients.
  • Modifying the processes of oceanic upwelling or downwelling so as to increase the rate at which atmospheric carbon is transferred to the deep sea.

The RoyalSociety Report finds that “removalof CO2 from the atmosphere is technically possible,” but it concludes that all of the carbon dioxide removal methods it considered “have a slow effect on the climate system due to the long residence time of CO2 in the atmosphere and so do not present an option for rapid reduction of globaltemperatures” (the Report discusses ocean fertilization, a method that has been the subject of controversy, at pages 16-19).  Since the focus here is on the potential of geoengineering to prevent near-term disasters due to global warming, these techniques won’t be discussed any further.

In the solar radiation management (SRM) category of geoengineering methods, the Royal Society Report analyzes four basic techniques for managing incoming solar radiation so as to reduce the amount of heat that is absorbed by greenhouse gases (RS Report, pp. 23-36). They are:

  • Brightening the earth’s surface (e.g., by painting roofs, roads, and pavements white).
  • Making clouds brighter (e.g., by injecting sea-salt particles into ocean clouds).
  • Placing reflective materials in space to shield the earth from solar radiation.
  • Injecting reflective particles into the stratosphere to block incoming solar radiation.

It should be noted at the outset that there are at least four general objections to use of SRM methods, all of which are recognized in the Royal Society Report. The first is that, while they may succeed in cooling the earth, these methods would do nothing to reduce the concentration of CO2 in the atmosphere. Therefore, they won’t affect impacts of a higher-CO2 world such as acidification of the oceans and the impact on plants of greater CO2 intake. In this respect, they differ from the slower-acting CO2 removal methods, which would lower the concentration of CO2.

A second general objection is that these methods, if successful, will have a “termination effect.” When use of the method is discontinued, the greenhouse gases present in the atmosphere will resume their warming effect and cause temperatures to increase rapidly to the level that would have prevailed had there been no blockage of sunlight. Since the rate of warming matters, this jump in temperature might cause more harm than if there had been no geoengineering activity.

A third drawback is that these methods would return the earth only to an approximation of its earlier temperature state. While it might be possible to lower the average global temperature to an earlier level, the variations of temperature across the earth would be different from those at the earlier time. This might affect rainfall patterns and other important environmental conditions.

A fourth objection is that the expectation of artificialcooling of the earth — or even the thought that it is possible — might reduce the willingness of citizens and politicians to take the hard steps necessary to reduce greenhouse gas emissions. The existence and extent of this effect are hard to measure in advance. Some havedismissed this fearas irrational (climate scientist Ken Caldera has said: “[T]hinking of geoengineering as a substitute for emissions reduction is analogous to saying, `Now that I’ve got the seatbelts on, I can just take my hands off the wheel and turn around and talk to people in the back seat.’ It’s crazy.”), but others think it’s a legitimate concern.

The Royal Society Report assesses each SRM method according to four criteria: (1) the time required both to implement the technique and to achieve the intended effect following implementation; (2) the cost of deployment and operation; (3) the method’s likely effectiveness in reducing temperature; and (4) the potential for unintended adverse consequences. The Report notes that its findings are rough estimates, and that more research is needed to refine them.

The Report finds that brightening the earth’s surface would only have regional effects on temperature. It concludes that those effects would be relatively minor unless they involved broad areas of the earth’s surface outside urban areas, such as deserts or vegetated regions, in which case the method would be very expensive and would have problematic impacts on ecosystems and/or agriculture.

The Report finds that making marine clouds brighter by injecting them with tiny grains from drops of seawater might achieve significant regional temperature reductions. However, it might cost several hundred billion dollars per year and might affect regional rainfall patterns and ocean currents. The Report concludes that “the approach may be useful in offering extra protection to particularly vulnerable regions like the Arctic.” (RS Report, p. 36) However, it warns that applying this technique in only one hemisphere might have a major adverse impact by changing the monsoons on which South Asian agriculture depends.

With respect to space-based methods, the Report notes that these methods have the potential to cool the entire earth. As a result, they would have an especially powerful “termination effect,” because global temperatures would rise rapidly if they were discontinued.

One space-based approach would deflect sunlight away from the earthby placing reflectivematerials either in near-earthorbits or farther away. The disadvantage of the near-earth-orbit approach is that the reflectivematerials eventually would be brought back to earthby gravity or scattered by the “light pressure” exerted by sunlight. That would necessitate periodic, expensive replacement. The RoyalSociety Report finds that a more promising approach would be to place reflectors at the “L1 point” about 900,000 miles from earth, where the gravitationalforces exerted by the sun and by the earth are equal. Various types of reflectors havebeen proposed. The Report finds that this method would be very expensive to initiate and couldn’t be implemented in less than a few decades. However, if the time frame for geoengineering efforts were a matter of centuries, the Report concludes that this approach might be cost-effective. It would have the advantage of not releasing materials into the atmosphere, thus avoiding possible adverse environmental impacts, but it too would have a “termination effect” when it ended.

Injection of Sulphur Aerosols into the Stratosphere

The final space-based approach would be to inject reflective particles into the stratosphere in the form of aerosols. The climatic impacts of this method would be similar to those of major volcanic eruptions. For example, the 1991 eruption of Mount Pinatubo in the Philippines injected large amounts of sulphur aerosols into the atmosphere. The resulting aerosol cloud spread around the globe and remained in the atmosphere for several years. According to experts from the US Geological Survey, this cloud “caused dramatic decreases in the amount of net radiation reaching the Earth’s surface,” resulting in “an observed surface cooling in the Northern Hemisphere of up to 0.5 to 0.6″ degrees Centigrade, or 0.9 to 1.0 degrees Fahrenheit. (Stephen Self, et al., “The Atmospheric Impact of the 1991 Mount Pinatubo Eruption,”

Assessing the aerosol-injection approach using the four criteria listed above, the Royal Society Report finds that the method would be timely, in that it could be implemented relatively quickly, perhaps via a fleet of custom-built aircraft, and cooling would begin within a year. The Report concludes that the method would be relatively cheap and that the annual cost could be measured in tens of billions of dollars.

The Report also finds that the aerosol-injection method would be effective in reducing temperatures, as demonstrated by the cooling that has occurred following volcanic eruptions. The magnitude of the reduction would be essentially unlimited, depending on the amount of particles that were injected. Depending on the geographic pattern of the injections, the reduction could be either global or regional. The Report notes that there have been several climate modeling studies of the results of injecting sulphates into the stratosphere. While observing that these studies involved simplifications of the climate system, the Report says:

a first-order conclusion is that the model climate, withboth increased greenhouse gases and enhanced sulphate aerosol, is much closer to the present day climate than is the case withjust increased greenhouse gases. . . . A general conclusion from these studies is that geoengineering with stratospheric aerosols could, in principle, be used as a means to counteract the first-order, global effects of increased greenhouse gas concentrations. (RS Report, pp. 43, 45)

With respect to the fourth criterion, the likelihood of unacceptable adverse environmental impacts, the Report notes that research following the Mount Pinatubo eruption reached the following conclusions (RS Report, pp. 31-32):

  • Observations found decreased rainfall over land areas, resulting in less runoff and reduced river discharges.
  • Climate models suggested that there would be changes in the Asian and African summer monsoons that would reduce rainfall and potentially affect the food supply for billions of people.
  • Studies found a 2% reduction in the stratospheric ozone layer, which could delay the natural repair of the “ozone hole” over Antarctica.
  • Sulphur injection might have other effects on stratospheric ozone in the middle latitudes.
  • There might be environmental impacts due to heating of the lower stratosphere in the tropics.
  • There might be changes in surface water and soil moisture and in the intensity of solar radiation at the Earth’s surface, with impacts on the biosphere.
  • There isn’t likely to be a significant increase in acid rain, because the amount of sulphur injected would be much less than that emitted by volcanoes and industry.

The Report states that all the findings in this list must be considered tentative, and that much more research is needed to identify the likely impacts of injecting sulphur particles. The Report notes that studies carried out following volcanic eruptions provide some evidence of the likely impacts, but that there has been relatively little research in the context of geoengineering. One major difference between the two situations is that the sulphur injections from volcanoes last a relatively short time, whereas a geoengineered sulphur layer would be designed to persist longer.

Unfortunately, it appears that the only reliable way of verifying the environmental impacts of the sulphur-injection method would be to conduct a global or regionalexperiment. That experiment would affect the climate of the entire earth, or a large part of it. Moreover, some analysts have concluded that such a test would have to continue for at least ten years, because “weather and climate variability preclude observation of the climate response without a large, decade-long forcing.” (Robock, A., et al., “A Test for Geoengineering,” Science, vol. 327, p. 530 (29 Jan. 2010)).

The aerosol-injection technique shares with the other solar radiation management approaches the drawback that it would have a “termination effect.” If the sulphur layer were maintained for a number of years, the world would experience a nasty shock if it ended quickly for any reason, including the discovery of unacceptable adverse impacts, since temperatures would increase substantially and would rise more rapidly than if geoengineering had not occurred. The rise in temperature would be proportional to the CO2 level in the atmosphere, so it would be larger to the extent that emission reduction efforts hadn’t succeeded in moderating CO2 emissions during the period when the artificial sulphur layer was maintained.

After its survey of the various methods of managing solar radiation, the Royal Society Report concludes:

None of the methods assessed are yet ready for deployment, and all require significant research including in some cases, pilot scale trials, to establish their potential effectiveness and effects on climatic parameters including temperature and precipitation at both the global and regional scales.

Of the methods assessed the global techniques appear to be the safest methods for reducing global average temperature. The early stage of development of the various space based methods proposed, and their high R&D costs relative to the other global methods mean that they are unlikely to be feasible in the medium term. Stratospheric aerosols therefore appear to be the most promising as they could be more rapidly developed and implemented than the space based methods. However, significant R&D would be required to identify and evaluate potential impacts on the hydrological cycle, stratospheric ozone and on the biosphere prior to deployment. (RS Report, p. 36)

Discussion and analysis of the aerosol-injection method intensified following the publication in August 2006 of an essay in the journal Climatic Change by Dr. Paul Crutzen, a Dutch atmospheric chemist who won the Nobel Prize in 1995 for his work on depletion of the stratospheric ozone layer. In that essay, Crutzencalled for research into the possibility of injecting tiny sulfate aerosols into the atmosphere via balloons or shells from artillery guns, in order to reflect sunlight and cool the earth. Crutzen estimated that this could be done at a cost of $25-50 billion dollars a year. ( In the same issue of Climatic Change, Dr. Ralph Cicerone, a highly respected atmospheric chemist who was (and is) the president of the US National Academy of Sciences, wrote in support of Crutzen’s proposal for more research. Another prominent climate researcher, Tom Wigley, suggested a similar approach at about the same time. (T. M. L. Wigley, “A Combined Mitigation/Geoengineering Approach to Climate Stabilization,” Science, vol. 314, p. 452 (20 Oct. 2006)).

A broad-ranging discussion of Crutzen’s idea took place in November 2007 at a workshop in Cambridge, Massachusetts, organized by Harvard University and the University of Calgary. The participants included 50 experts in climate science, energy, and economics. According to a report published in Science magazine, the group “gave a qualified `yes’” to the question whether “scientists [should] study novel ways of altering Earth’s climate to counteract global warming.” (Eli Kintisch, “Scientists Say Continued Warming Warrants Closer Look at Drastic Fixes,” Science, vol. 318, p. 1054 (16 Nov. 2007))

According to the Science article, workshop participants estimated that the aerosol injection approach suggested by Crutzen could be implemented at a cost of “a few billion dollars a year.” However, some were concerned that geoengineering efforts might diminish public and political support for reducing carbon emissions, which was found to be the preferable solution (Crutzen expressed the same concern in his 2006 article).

In 2008, atmospheric scientist Philip Rasch and others published a useful summary entitled “An overview of geoengineering of climate using stratospheric sulphate aerosols.” ( They concluded that injection of “sulphate aerosols could counteract the globally averaged temperature increase associated withincreasing greenhouse gases, and reduce changes to some other components of the Earth system,” but that “many uncertainties remain in understanding the influence of geoengineering on the climate system (particularly on aspects related to likely impacts on the biosphere).

Other Significant Discussions and Initiatives

There have been other important discussions and initiatives with respect to geoengineering in both scientific and policy contexts. They include:

  • A 2009 article by in Foreign Affairs magazine by Professor David Victor and a multidisciplinary group of co-authors that called for “a serious and transparent international research effort,” citing, among other reasons, the chance that a single national government or even private sector actors might implement a geoengineering scheme. (D. Victor, et al., “The Geoengineering Option: A Last Resort Against Global Warming?” Foreign Affairs, vol. 2, no. 88, March/April 2009).
  • “America’s Climate Choices,” a suite of studies sponsored by the US. National Academies and designed to inform and guide responses to climate change across the nation. (See Experts representing various levels of government, the private sector, nongovernmental organizations, and research and academic institutions were selected to serve on four panels and an overarching committee. Two of the project’s reports — on climate science and ways of limiting the magnitude of climate change — have been cited previously.
  • Three hearings on geoengineering that were held by the U.S. House Committee on Science and Technology in 2009-2010, in coordination with the corresponding committee of the UK House of Commons. In October 2010, Committee Chairman Bart Gordon (who did not run for reelection in 2010) issued under his own name a thoughtful draft report entitled “Engineering the Climate: Research Needs and Strategies for International Coordination.” The hearing records and the report can be found at
  • At the request of House Committee on Science and Technology Chairman Bart Gordon, the Government Accountability Office carried out a wide-ranging study that resulted in an October 23, 2010, report entitled “A Coordinated Strategy Could Focus Federal Geoengineering Research and Inform
    Governance Efforts” (
  • January 2010 opinion piece in the scientific journal Nature by energy and climate scientist David Keith and others that recommends “a carefully designed, incremental, transparent and international programme of [solar radiation management] research; and linked activities to create norms and understanding for international governance . . . .” The recommended research program would include field testing; the recommended budget would grow within a decade to $1 billion a year. (D. Keith, et al., Nature, vol. 463, p. 426 (28 Jan. 2010))
  • A March 2010 meeting of 175 scientists and others at the Asilomar conference center in California to discuss issues relating to geoengineering research. A post-conference statement by the organizing committee stated that “it is … important to initiate further research in all relevant disciplines to better understand and communicate whether additional strategies to moderate future climate change are, or are not, viable, appropriate and ethical,” and that the conference was intended to facilitate “a process involving broader public participation [which] should ensure that research on this issue progresses in a timely, safe, ethical and transparent manner, addressing social, humanitarian and environmental issues.” (
  • The formation in March 2010 by the National Commission on Energy Policy, a bipartisan nongovernmental organization, of a Task Force on Geoengineering. The Task Force consists of experts in science, technology, diplomacy, national security, ethics, and law, including some staff members of major environmental groups. The Task Force is charged with issuing recommendations concerning U.S. policy on geoengineering research and governance.
  • Also in March 2010, Britain’s Royal Society announced the Solar Radiation Management Governance Initiative, an effort to “ensure strict governance of any plans for solar radiation management (SRM) geoengineering … in partnership with the Academy of Sciences for the Developing World, and the Environmental Defense Fund.”   The Initiative will issue recommendations for governance of geoengineering research late in 2010. See

Two books on geoengineering aimed at a mass audience were published in the spring of 2010: How to Cool the Planet: Geoengineering and the Audacious Quest to Fix Earth’s Climate, by Jeff Goodell, and Hack the Planet: Science’s Best Hope — or Worst Nightmare — for Averting Climate Catastrophe, by Eli Kintisch. While the appearance of these books is a mark of the subject’s growing popularity, the fact that in the summer of 2010 Goodell’s book stood at #68,462 on Amazon’s “Bestsellers Rank” and Kintisch’s at #82,241 suggests that geoengineering isn’t yet a household word. Both books provide a useful, objective overview, with interesting information about the scientists involved in geoengineering research.

VI Geoengineering Research and Establishment of Governance Mechanisms Should Be an Urgent Priority

Few if any people favor immediate use of geoengineering to bring about a reduction in the earth’s temperature by the only method that is apparently available: injecting sulphate aerosols into the stratosphere. Despite humanity’s relatively benign experience with volcanic eruptions, the environmental impacts of this type of geoengineering remain uncertain. An experiment to verify the nature of those impacts would itself alter the climate over large regions, if not the entire globe. And there exists no decisionmaking process to legitimize an experiment that would affect climate on so broad a scale.

The concern about unregulated geoengineering experiments was given some legal force when the 193 nations that are parties to the UN Convention on Biological Diversity adopted at their October 2010 meeting in Nagoya, Japan, a resolution providing:

that no climate-related geo-engineering activities that may affect biodiversity [may] take place, until there is an adequate scientific basis on which to justify such activities and appropriate consideration of the associated risks for the environment and biodiversity and associated social, economic and cultural impacts, with the exception of small-scale scientific research studies. (See Juliet Eilperin, “Geoengineering sparks international ban, first-ever congressional report,” Washington Post, Oct. 29, 2010.)

Some have described this resolution as imposing a “de facto moratorium” on geoengineering experiments. However, the resolution by its terms covers only actions that “affect biodiversity,” and it’s not clear what that means. It should be noted that the United States isn’t a party to the Convention, and therefore isn’t bound by the resolution. Nevertheless, the resolution demonstrates that there is widespread concern about the possible effects of geoengineering activities and underlines the need for additional scientific research and for institutions that can assess the risks of proposed activities so as to satisfy the criteria set forth in the resolution.

The question, then, is how urgently we should pursue the research and institution-building that must precede any use of geoengineering to reduce global temperatures. Many discussions of geoengineering appear to assume that we can proceed in a leisurely fashion, an assumption reflected in the frequent descriptions of geoengineering as a “method of last resort.” The problem with this mindsetis that it ignores both the severe harm from climate change that is predicted to occur or become inevitable within a few decades, or even a few years, and the real possibility that we will experience sudden, catastrophic effects that are now thought to be unlikely.

With respect to the latter concern, it’s sometimes said in justification of the “last resort” approach that we should plan to use geoengineering only when we perceive that the earth’s geophysical/biological systems are approaching a tipping point that would trigger a “doomsday effect” or “climatic disaster” like shutting down the Gulf Stream or a gigantic release of methane from permafrost (see, e.g., D. Victor, et al.,” The Geoengineering Option: A Last Resort Against Global Warming?” Foreign Affairs, vol. 2, no. 88, March/April 2009). But the Earth’s systems are so complex that we may not discover that we’re near a tipping point until we have passed the point of no return and disaster has become inevitable.

As a thought experiment, let’s assume that geoengineering by injecting sulphur aerosols into the stratosphere has been thoroughly studied by scientists, and that the adverse environmental impacts are predicted to be relatively minor, though somewhat uncertain. Let’s assume also that the great majority of the world’s nations have entered into a global agreement establishing a process for making geoengineering decisions. In these circumstances, the issue would be whether to undertake a temporary global experiment to determine the actual environmental impacts of aerosol injection.

Even today, when the adverse impacts of global warming have only begun to be felt, it’s likely that there would be serious debate about this issue. Those in favor of conducting the experiment might include:

  • Conservationists who believethat preventing the extinction of a large proportion of the earth’s terrestrial species, as well as enormous adverse impacts on marine ecosystems, is hugely valuable, and who recognize that the number of species and ecosystems doomed to extinction is increasing year by year.
  • Scientists and others who think we should act to prevent major feedback effects that will accelerate global warming, such as the loss of Arctic summer sea ice.
  • Low-lying nations that deem it essential to halt or reverse sea-level rise, which in some cases threatens their very survival.
  • Those who believe we should reduce the incidence and severity of future hurricanes, wildfires, and droughts, and save the earth from a future in which continually rising temperatures will play havoc with regional precipitation patterns and therefore with agriculture.
  • Those who fear that continually rising global temperatures will bring us to a “tipping point” that results in a super-catastrophe, such as the “shutting down” of the Gulf Stream or an extremely large rise in sea level.

Those on the other side might include:

  • Those who fear that, despite scientists’ predictions, the aerosol-injection experiment would cause enormous, irreparable harm by altering key weather patterns, such as Asian monsoons; might alter regional weather patterns across the globe in less drastic ways that cumulatively might have devastating effects; or might do serious damage to the ozone layer.
  • Those who want to delay the experiment in order to allow more time for research to narrow the uncertainties about the experiment’s environmental impacts.
  • Those who believe the experiment, by highlighting the possibility, or even demonstrating, that geoengineering could prevent the adverse effects of higher temperatures (though not other effects of greenhouse gas buildup, such as ocean acidification), would sap the political will that is needed to reduce greenhouse gas emissions.
  • Nations, commercialinterests, and others who calculate that they would benefit from a warmer earth.

It’s not clear who would prevail in this hypothetical debate. However, the list of arguments in favor of the experiment strongly suggests that geoengineering should be regarded as something more than a last resort. Moreover, it’s probable that the adverse effects of global warming will increase as time goes on. If so, the case for carrying out the aerosol-injection experiment will become stronger, provided that researchers don’t discover unacceptable environmental impacts. The pro-experiment case could become overwhelming if scientists find, or real-world events reveal, that the adverse effects of warming are likely to be much worse than now predicted. If that happens before the scientific and institutional work that should precede any use of geoengineering has been completed, humanity will be faced with very hard choices.

In any event, the basis for weighing the predicted impacts of a geoengineering experiment should not be a comparison of those impacts with the current environmental status quo. Instead, those impacts must be compared with the environmental conditions that are predicted to exist if global warming continues, taking into account likely efforts to reduce greenhouse gas emissions. Many people might conclude that a future in which average global temperatures return to past levels, albeit with regional variations and some adverse impacts, is likely to be less risky than one in which ever-rising temperatures continue to reach levels never experienced by human civilizations. We must never forget that humanity is now engaged in a massive, inadvertent geoengineering project, and that the future offers no risk-free options.

It’s not certain that the pro-experiment forces eventually will win the argument about an aerosol-injection experiment. After all, we don’t know what adverse effects will be revealed by further research. It’s far from certain that a sufficient number of nations will agree on a process for approving such an experiment. If a process is established, the participants might decide to deny permission for the experiment even in the face of strong evidence of harm from global warming, especially if the experiment must last for many years to be valid.

The point is that the arguments in favor of carrying out the experiment are powerful, and are likely to grow more powerful. They may become overwhelming if scientists find a strong likelihood of truly catastrophic, near-term effects unless the rise in global temperatures is halted or reversed. To deny ourselves the geoengineering option because of delays in scientific research and in building the necessary institutions could lead to enormous harm that otherwise might be avoided. Climate scientist Ken Caldeira has observed: “If I had to wager, I would wager that we would never deploy any geoengineering system, and that we’re more likely just to try our best to adapt to it. . . . But we’re obviously interfering with the climate system wholesale now, and it’s possible that more intelligent interference could reduce the damage from the first interference. But it could make it worse. I don’t think we know, which is why we need the research program.” (

As noted previously, some people fear that a geoengineeringexperiment, or even a robust research program, would weaken efforts to reduce emissions. However, there are obvious reasons why that temptation should be rejected. There is a significant chance that research will reveal adverse effects that make geoengineering via injection of sulphur aerosols unacceptable. Moreover, emission reductions are the only way of avoiding the need for ever-stronger actions to reduce the earth’s temperature, and are the only remedy for the very important problem of acidification of the oceans. They should be pursued as vigorously as possible. Those who say that we must choose between the two approaches are posing a false dichotomy, since there is no direct conflict between them. With the fate of our planet at stake, we should be able to walk and chew gum at the same time.

VII Next Steps

There is an urgent need for much more scientific research on geoengineering. Equally important, nations together with relevant intergovernmental and nongovernmental organizations should move rapidly to draft and negotiate a global treaty that establishes a process for approving geoengineering actions that would have transnationalimpacts, including both geoengineering experiments and full-scale use of geoengineering methods.

A Robust Scientific Research Program

If geoengineering is to become a real option, there is an urgent need for more information about the actions that might lower temperatures, the economic costs of those actions, and especially their likely environmentalimpacts. To gain that knowledge, nations and international organizations should agree on and implement as soon as possible a robust, well-supported, internationally coordinated program of scientific research. In the meantime, countries should push ahead with national and regional research programs.

The 2009 RoyalSociety Report calls for strong research programs both at the global and European levels and within the United Kingdom. (RS Report, pp. 61-62) It states: “A realistic cost for a UK programme of research on geoengineering would be of the order of £10M [$15 million] per annum.”

The research effort has scarcely begun. As noted previously, there has been some scientific research on geoengineering. But the scale of that research is small, and no government appears to have established a significant, coordinated research program. The United States has no semblance of such an effort. President Obama’s Science Adviser, John Holdren, told the Associated Press in April 2009 that geoengineering “[has] got to be looked at” as part of the U.S. Government’s efforts on climate change, but the next day he denied that “the White House is giving serious consideration to geo-engineering.” Little has been heard from the US Executive Branch since then.

The May 2010 National Research Council report entitled “Advancing the Science of Climate Change,” cited previously, devotes 9 pages to a discussion of SRM methods; the last 2 ½ pages discuss research needs in the areas of science and engineering, ethics, and governance. (see The Report recommends an “integrated research effort.” But it conveys no sense of urgency, doesn’t suggest a lead agency, and doesn’t recommend a specific budget.

The October 2010 report by the Government Accountability Office, “A Coordinated Strategy Could Focus Federal Geoengineering Research and Inform Governance Efforts,” contains a lengthy compendium of federal research efforts relevant to geoengineering. See However, the GAOP found that found that “it was difficult to determine the full extent of federal geoengineering research activities because there is no coordinated federal strategy for geoengineering.” The GAO Report recommends that the U.S. Government “develop a clear, defined, and coordinated approach to geoengineering research in the context of a federal strategy to address climate change ….”

U.S. political leaders should recognize that, at the least, the geoengineering option offers the possibility of insurance against climate catastrophes, and that we need the option as soon as possible. They should establish a U.S. research program like the one the Royal Society has recommended for Britain. It’s essential that that program be effectively coordinated. A variety of possible coordination mechanisms are discussed in the Gordon Report that was described in Part VI.

The research program must be adequately funded. If the $15 annual budget recommended by the Royal Society is appropriate for Britain, it follows that the budget for the U.S. program should be several times as large. In addition, the United States should urge other nations to increase their research, with the aim of creating a strong, coordinated global effort.

In the real world, where partisan conflict is intense and a relatively modest effort to control greenhouse gas emissions hasn’t prevailed in the Congress, the establishment and funding of this kind of research program will require strong leadership from the President and influential Members of Congress. Much will depend on the position taken by U.S. environmental groups, a subject discussed at the end of this chapter.

At the global level, the IPCC is an obvious candidate to review and assess knowledge about geoengineering and present the results in terms policymakers can understand. Some scientists have suggested that the IPCC should include geoengineering in its next assessment report. That seems desirable. The goal of that assessment should not be to reach final conclusions about the merits of any particular approach but to state what is known, identify questions that need to be answered, and describe the research that will be needed to provide those answers.

Mechanisms for Governance, Including a Global Treaty

Some scientific research is going on, and the need for a strong, coordinated research program is being discussed at least within the scientific community. By contrast, the need to construct a decisionmaking framework that can authorize geoengineering research and deployment that might have significant transnational impacts has largely been neglected. Yet the establishment of that framework, which is essential to any large-scale geoengineering experiment, is likely to take longer than the scientific research that must precede the experiment. Therefore, it must be an urgent priority.

Without rapid development of governance mechanisms there is a danger that piecemeal moratoria like the one adopted by the parties to the Convention on Biological Diversity will stifle badly needed research. House Science and Technology Chairman Bart Gordon stated in the draft report he issued in October 2010:

[T]he impact of a moratorium on research should be carefully weighed against the importance of promoting scientific freedom and accountability. Scientific research and risk assessment is essential to developing an adequate scientific basis on which to justify or prohibit any action related to climate change, including climate engineering activities. Sound science should be used to support decision making at all levels, including rigorous and exhaustive examination of both the dangers and the value of individual climate engineering strategies. A research moratoria that stifles science, especially at this stage in our understanding of climate engineering’s risks and benefits, is a step in the wrong direction and undercuts the importance of scientific transparency. The global community is best served by research that is both open and accountable. If climate change is indeed one of the greatest long-term threats to biological diversity and human welfare, then failing to understand all of our options is also a threat to biodiversity and human welfare. “Engineering the Climate: Research Needs and Strategies for International Coordination,”

A code of conduct for research as a first step. The Royal Society Report declares:

An internationally agreed (but initially voluntary) code of conduct and system for approval for geoengineering research would be highly desirable. This should include provisions for appropriate environmental monitoring and reporting, depending on the magnitude and spatial scale of the experiments. The emerging London Convention and Protocol system for regulation of ocean iron fertilisation experiments may be a model for this. . . . Only experiments with effects that would in aggregate exceed some agreed minimum (de minimis) level would need to be subject to such regulation. (RS Report, pp. 65-66)

The Report goes on to conclude:

The Royal Society in collaboration withinternational scientific partners should develop a code of practice for geoengineeringresearch and provide recommendations to the international scientific community for a voluntary research governance framework. This should provide guidance and transparency for geoengineering research and apply to researchers working in the public, private and commercial sectors. It should include:
a) Consideration of what types and scales of research require regulation including validation and monitoring;
b) The establishment of a de minimis standard for regulation of research;
c) Guidance on the evaluation of methods including relevant criteria, and life cycle and carbon/climate accounting.
(RS Report, p. 75)

As noted in Part VI above, the Solar Radiation Management Governance Initiative that was launched by the Society in March 2010 will issue late in 2010 recommendations for governance of geoengineering research. See

The need for a global treaty to regulate geoengineering. There are at least two reasons why a global treaty, not just a code of conduct, will be needed to regulate geoengineeringefforts that might affect the temperature of the earth as a whole or of large regions. First, it’s widely agreed that it would be wrong for any single nation or small group of nations, much less a set of private actors,  to carry out a geoengineering experiment that would affect the climate beyond the boundaries of the sponsoring countries. Because others would be affected, basic principles of fairness require that all those who would be affected be informed about the proposed action and be allowed them to participate in the decision whether to carry it out. This applies with special force to an experiment – much less a full-scale effort – to reduce global or regional temperatures by injecting aerosols into the stratosphere. This point is well made in the 2009 Foreign Affairs article that was cited in the last section.

Ensuring fairness to those affected isn’t the only reason why we need a global regime to govern geoengineering. A second reason is that, as shown by the preceding analysis, we are very likely to need such a framework in order to carry out the research that is necessary to find out whether geoengineering can be a real option for reversing the global rise in temperature.

Some scientists and others have expressed the hope that well-intentioned, well-justified experiments to explore the potential of the sulphur-injection method could proceed in the absence of such a treaty (see, e.g., D. Victor, et al., “The Geoengineering Option: A Last Resort Against GlobalWarming?” Foreign Affairs, vol. 2, no. 88, March/April 2009). But the very purpose of an experiment of that kind would be to affect the climate of the whole earth, or at least of large regions (for example, scientist Michael MacCracken has suggested the possibility of injecting short-lived sulphur aerosols into the troposphere over the Arctic in summer to prevent melting of glaciers and sea ice; see ”Geoengineering to moderate specific impacts,” Environ. Res. Lett., vol. 4, no. 4 (2009)). It has been suggested that such an experiment may have to last for many years. The environmental impacts are bound to be uncertain despite predictions based on the best computer models. Indeed, one purpose of the experiment will be to verify those impacts.

The concern about the impact of geoengineering activities that was reflected in the resolution adopted by the parties to the Convention on BiologicalDiversity discussed above in Part VI demonstrates that such a proposed experiment would undergo intense scrutiny. Even if it wasn’t banned by the resolution, or was alleged to be authorized under the resolution’s terms, it seems certain that some nations, or at least politically influential citizen groups, would object. The issue would surely make its way to agencies of the United Nations and to other intergovernmental bodies, triggering an ad hoc international decisionmaking process involving scientific and political debate. That process might culminate in a vote by the UN General Assembly, since some nations would be likely to question the authority and suitability of the other UN bodies — including the Security Council — to make such a decision, since they aren’t representative of all nations and, in the case of the Security Council, some countries have veto power.

Professor David Victor, a co-author of the Foreign Affairs article, has expressed the view that it’s too early to negotiate a geoengineering treaty because the negotiations would likely end in a stalemate between nations favoring a total ban and countries desiring to leave the geoengineering option open. (D. Victor, “On the Regulation of Geoengineering,” Oxford Review of Economic Policy, Volume 24, Number 2, 2008, pp.322–336) It certainly would be unwise to begin actualnegotiation of a treaty without a substantial preparatory process to discover whether the time is right. The draft treaty that is put forward for negotiation should be prepared with input from experts from key countries and from many parts of the world. The treaty should not itself authorize any geoengineering experiment or deployment that would have significant transnational impacts. Instead, it should provide criteria by which proposed geoengineering projects are to be judged and approved or disapproved, as well as outlawing unapproved geoengineering activities that would have significant transnational impacts. These conditions should minimize the likelihood of a stalemate in the negotiations.

The U.K. House of Commons Science and Technology Committee reached a similar conclusion in its March 2010 report on “The Regulation of Geoengineering” ( The Committee stated: “While accepting that the development of a `top-down’ regulatory framework may have risks and limitations, we consider that these are outweighed by the benefits of an international framework: legitimacy; scientific standards; oversight mechanisms; and management of environmental and trans-boundary risks.” (Conclusion # 11).

It’s widely agreed that no existing treaty meets the need for an international process to regulate, and authorize when appropriate, actions aimed lowering the earth’s temperature. It follows that nations, together with relevant intergovernmental and nongovernmental organizations, should move with prudent speed to draft and negotiate a globaltreaty that establishes a mechanism for approving both geoengineering experiments and full-scale use of geoengineering methods with transnational impacts, and for prohibiting unauthorized actions. The geoengineering treaty might constitute a protocol to the UN Framework Convention on Climate Change.

The task of drafting and obtaining agreement on a geoengineering treaty is bound to take considerable time. At the outset, it will be necessary to overcome the widespread view that geoengineering is a “far out” idea akin to science fiction, and that consideration of the geoengineering option implies that one is abandoning serious efforts to reduce emissions. The diverging viewpoints described in the “thought experiment” discussion in the last section are certain to affect the negotiation of a geoengineering treaty, as well as decisions taken pursuant to the treaty. Each nation is sure to calculate carefully whether it might benefit from a warmer world or might suffer disproportionate harm from geoengineering activities.

A geoengineering treaty should:

  • Be open to all nations.
  • Include a strong scientific advisory group that includes experts from many countries.
  • Cover all geoengineering activities that might have significant transnational impacts; state what types of activities are exempted; and specify the process for determining whether a proposed activity is exempt.
  • Provide that nations and nongovernmental actors may not engage in or facilitate geoengineering activities covered by the treaty, either on their territories or within the global commons (including outer space), unless those activities are approved pursuant to the treaty, and specify penalties for violation of that prohibition (difficult issues include what body would have power to decide there has been a violation; the nature of the penalties if there has been a violation; and how to enforce the prohibition when the violator isn’t a party to the treaty).
  • Describe the analyses that must be carried out prior to a decision whether or not to approve a proposed geoengineering activity and the procedures for publicizing those analyses and receiving comments on them.
  • Set forth the procedure for deciding whether to authorize a proposed geoengineering activity (this is likely to be the most difficult issue to be resolved in the negotiations).
  • Perhaps set forth the circumstances in which those who claim to be injured by an authorized or unauthorized geoengineering activity can seek and receive compensation (this would involve difficult issues such as the standard for proving that the activity caused the injury and who would be liable to pay the compensation).

A geoengineering treaty would differ from many environmental treaties in that it would be intended to authorize activities as well as to prohibit them. If the treaty is to have a realistic prospect of approving any experiments that might have widespread impacts — a category that includes any effort that might reduce global or regional temperatures — careful attention must be paid to the composition and role of the scientific advisory body and to the decisionmaking process for approving or rejecting proposed experiments. For example, there may be a practicalneed to allow proposals to be approved by less than a unanimous (or “consensus”) vote of the parties to the treaty, even though this would be contrary to the practice under many international agreements.

Discussion of the relevant issues should take place in a variety of fora, and should lead to the preparation of a negotiating draft of such a treaty. The best catalyst for preparing that draft might be an intergovernmental body or a respected international NGO, such as the International Union for Conservation of Nature. The process of preparing a draft should involve legal experts from many parts of the world. After extensive discussion, a final draft should form the basis for negotiations under the auspices of a global intergovernmental body.

The Role of Citizen Groups

In the United States and in Europe, governmental initiatives affecting the environment commonly require strong support from politically influential interest groups. Except for the groundswell in the scientific community, no such support has emerged for geoengineering research or negotiation of a treaty on geoengineering. Environmental citizen groups in the United States and Europe, which have political clout and a strong interest in climate change, are sure to play a major role by either promoting or opposing serious consideration of the geoengineering option. At this point, most of the major groups in the United States and Europe haven’t taken an overall position. None is lobbying for a strong research program or the negotiation of a treaty, but none is calling for a ban on geoengineering or opposing a research program. As was noted previously, the Environmental Defense Fund has joined with the British Royal Society in the Solar Radiation Management Governance Initiative, an effort to ensure effective regulation of actions aimed at solar radiation management geoengineering.

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