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Updated 16 November 2004
Consequences (title)
Consequences Vol. 5, No. 1, 1999


See also: article overview






Beyond Kyoto:
Toward A Technology
Greenhouse Strategy

A review assessment published in

CONSEQUENCES vol 5 no 1 1999, pp. 17-28

During the first two weeks in December of 1997 representatives of more than 130 of the world’s nations gathered in Kyoto, Japan to consider next steps to be taken by the international community in confronting the issue of global climate change. The culmination of their deliberations was a draft document, or protocol, for later ratification by the governments involved. The Kyoto Protocol was neither the first nor the last step in a long journey toward finding an appropriate response to the challenge of ever-increasing amounts of carbon dioxide and other greenhouse gases in the atmosphere. A great deal remains to be done to forge a draft agreement into a lasting and effective tool. That work, moreover, must be done in the laboratory and market place as well as around the negotiating table.

Out of Hawaii

The origins of the global greenhouse warming issue are deeply rooted in scientific findings, and can be traced to a set of observations, initiated during the 1958 International Geophysical Year, when David Keeling at the Scripps Institute of Oceanography first began to compile a continuous record of the concentration of carbon dioxide (CO2) in the air. To minimize the effects of local pollution, Keeling set up an observatory near the top of Mauna Loa, a towering mountain on the island of Hawaii.

The average concentration for 1959, the first complete year of Keeling's measurements, was 316 parts per million by volume (ppmv) – or slightly more than 0.03% of the sampled volume of air. By 1998, the concentration had climbed steadily upward to 367 ppmv, approaching 0.04% by volume (see Box below). In the meantime, other scientists were able to demonstrate that the inexorable increase that Keeling was measuring had started long before any of us was born.

Glaciologists were able to extend the Mauna Loa measurements backward in time, by measuring the amount of CO2 in tiny bubbles of air that had been trapped and preserved in accurately-dated ice cores, drawn from Arctic and Antarctic glaciers. These time capsules from the past revealed that the amount of CO2 in the air of long ago had held quite steady at roughly 260 to 280 ppmv for thousands of years. Then, beginning roughly 300 years ago, it started to climb: first slowly, then – as time went by – faster and faster. The rise coincides with a period of time when new lands were being cleared for agriculture and settlement, releasing more carbon into the air, and later, with the start of the Industrial Revolution when first coal and then oil came into heavy use. Today there is about 35 percent more carbon dioxide in the air than was the case in pre-industrial times. Nearly all of the increase has come from clearing land, and from burning coal, oil, and the refined products of petroleum. And almost all that we have added in the last 100 years is still there.

CO2 in the Air
in parts per million by volume

from ice cores and in bold, direct measurements
   4000 B.C. to about A.D. 1700 260-280
   1750 280
   1800 285
   1850 291
   1900 300
   1950 312
   1959 316
   1990 340
   1994 358
   1998 367
   2000 380?

The effects and causes of
more CO2

As we all know, CO2 is a "greenhouse gas" that serves as a kind of natural thermostat for the planet. When the amount of CO2 in the air increases, we can expect, in time, a change in the global climate, in the direction of warmer average surface temperatures. CO2 is one of a number of greenhouse gases that also include water vapor (H2O), methane (CH4), nitrous oxide (N2O), the chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs), and sulfur hexaflouride (SF6). Other components of the atmosphere also play an indirect role: a variety of gases such as carbon monoxide (CO), nitrogen oxides (NOx), and volatile organic compounds (VOCs) can affect the concentration of certain greenhouse gases through chemical reactions. The net cooling affect exerted by very fine particles in the air – called aerosols – and especially those containing sulfur, further complicates the relationship between human activities and climate. Thus, in the short run, reducing sulfur emissions, for example, by restricting the use of sulfurous coal, might do the climate more harm than good, since sulfur particles and CO2 in coal smoke have opposing effects on the temperature of the air.

Estimates vary as to the climatic consequence of doubling the pre-industrial concentration of CO2, but almost all climate researchers conclude that the average temperature, worldwide, will rise between 1.5 and 4.5 degrees Centigrade, or about 3 to 9°F. Interestingly, in spite of extensive research, this range of estimates in the projected increase has not narrowed in more than a decade. While our understanding of the climate system has expanded dramatically in recent years, so has our appreciation for the complexity of predicting long-term climate in more than the most general terms.

Evidence has mounted that the ever-increasing concentration of CO2 is most likely the result of our own activities – principally the burning of fossil fuels, mainly coal and oil, and deforestation. It now seems almost certain that in the absence of global policy restraints, we will eventually increase the amount of CO2 in the air above 550 ppmv before the end of the 21st century, which is a far richer mixture than any the Earth has known in at least the last 200,000 years.

Down to Rio

While meteorologists and other scientists had long been aware of the prospects for global greenhouse warming, the gravity of impending climate change was largely unknown outside of scientific circles until about ten years ago. In 1988 things changed. A combination of political and weather events in that year conspired to lift the issue out of the halls of academia and into the public consciousness. Since that time there has been continued open debate about the unrestrained accumulation of greenhouse gases in the atmosphere.

The birth of the FCCC

In 1990 the United Nations initiated a set of international discussions intended to lead to an international response to these concerns. What first came out of them was a document called the Framework Convention (i.e., an international agreement) on Climate Change (FCCC). The FCCC was formalized and signed by 155 nations at the "Earth Summit" in Rio de Janeiro, Brazil in June of 1992. As of June 1999 it had been endorsed by 179 parties, including most of the 185 member nations of the UN, and all the major greenhouse-gas-emitting countries of the world.

The FCCC is comprised of twenty-seven Articles, covering matters which range from lofty principles to more mundane definitions. The ultimate objective, underlined here, is set forth in Article 2:

The ultimate objective of the Convention and any related legal instruments that the Convention of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

The FCCC is a political response to a highly complex social and scientific problem, which differs in fundamental ways from other environmental issues with which policy makers are familiar, such as local and regional air or water pollution. One of the more significant of these differences is the complex way that the quantity of greenhouse gases that are emitted each year is related to the total amount that remains in the air.

Although the ultimate objective of the Convention was stated in terms of concentrations, the target ceiling was defined only qualitatively, in terms of "the level that would prevent dangerous anthropogenic interference with the climate system." More quantitative goals were attached to emissions of CO2. These proposed restrictions applied only to what were called the Annex I nations: the developed countries and those in economic transition (see Box below). By the terms of the FCCC, the more economically able nations and those with economies in transition were to strive to reduce emissions to 1990 levels, in the year 2000. No attempt was made to link the proposed reductions to any specific ceiling on concentrations. As the year 2000 draws near, it appears that only nations with special circumstances, such as the economies in transition (whose restructuring and economic malaise has reduced emissions without need for climate policy intervention) and a handful of other nations such as the reunified Germany (which shut down many inefficient facilities in the East) and the United Kingdom (which underwent a conversion from coal to North Sea gas), will meet the year 2000 goal.

Emissions vs. concentrations

The climate change issue – like that of stratospheric ozone and harmful ultraviolet radiation – has to do with the concentration of minor chemical constituents of the atmosphere: in this instance, principally CO2, CH4, N2O, and CFCs. In the case of more familiar pollutants in the air, such as carbon monoxide or sulfur dioxide, a concern about concentrations is wholly equivalent to a concern about emissions: that is, how much is there at any place and time is a good indication of how much is being added.

The climate problem is different, due to the fact that the gases involved, once released to the air, remain there for such a long time. The amount of CO2 – the most important of the greenhouse gases released by human activities – is the cumulative result of human activities over the last several hundred years. In the short run, how much is added each year makes but a modest incremental difference in concentration. Moreover, because of its long residence time, the CO2 that we release into the air is ultimately circulated throughout the global atmosphere: what anyone adds (or added, long ago) affects everyone, everywhere else. Nor is there much that can currently be done, beyond waiting for carbon dioxide to be slowly taken up by plants, accumulated in soils, dissolved in the waters of the oceans, or, in the very long run, deposited in rocks.

Implications for national and international policy

These features of carbon dioxide have important policy implications.

  • First, no single year's emissions—or reductions in emission—matter that much. It is the accumulated total that affects the climate.
  • Second, while some nations indeed contribute more than others, no single country's emissions are solely responsible for the build-up. Nor by acting alone, can any country fix the problem.
  • Third, regardless of what course the nations of the world follow, total annual global emissions, which have been rising throughout the last 300 years, must be forced to peak and then decline, if successively higher and higher concentrations are to be avoided. But, importantly, this does not mean that total emissions must decline immediately; nor does it mean that fossil fuel use need ever decline.

The grand challenge of the next century will be in finding ways to simultaneously preserve and improve the quality of life in both developed and developing nations. Ultimately, global emissions—and not merely those of the developed countries—must decline. If, for example, the world is to avoid CO2 concentrations that exceed 550 ppmv, its inhabitants must find ways to reduce average global emissions, per person, to 1990 levels or lower, by the end of the twenty-first century.

The Annex I Nations of the Rio FCCC
Australia Greece Poland
Austria Hungary Portugal
Belarus Iceland Romania
Belgium Ireland Russia
Bulgaria Italy Spain
Canada Japan Sweden
Czechoslovakia Latvia Switzerland
Denmark Lithuania Turkey
Estonia Luxembourg Ukraine
Finland Netherlands United Kingdom
France New Zealand United States
Germany Norway  

Economic consequences

Projections regarding the economic consequences of global greenhouse warming vary widely, as reflected in the Second Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), published in 1996. Estimates of the global economic consequences of doubling the pre-industrial concentration of CO2 disagree even as to whether the overall impact will be detrimental or beneficial. Some studies suggest that climatic conditions associated with CO2 concentrations of 550 ppmv would on average bring net economic benefits to the world, while others anticipate losses.

The divergence arises from the compounding effect of uncertainties (i) in the climate impacts of doubled CO2, and (ii) in quantifying and valuing the economic consequences of these environmental changes. The second of these is especially difficult in the case of those consequences of climate change that do not pass through markets, and hence are difficult to quantify in economic terms. Examples are the value of replacing a hardwood forest with pine, or with prairie; or the value of lost species of plants or animals. As the predicated CO2 concentration increases, however, disagreement as to the sign of the net economic impact tends to disappear. Virtually all analysts agree that large amounts of warming are undesirable.

The degree of urgency with which the international community has embraced the challenge of climate change cannot be easily explained in terms of economics alone, for the extent of disagreement among economists is too great. The more compelling motivations to act stem more likely from concerns about possible unforeseen and undesirable climatic surprises, and from fears that certain natural ecosystems will be seriously disrupted and that some species and ecosystems may disappear entirely.

Made In Japan

The Rio FCCC was not cast in stone, for there are provisions within it that call for review and revision at periodic Conferences of the signatory members, or "Parties." To date, four such conferences have been convened (see Box below). The first Conference of the Parties (COP-1) was held in Berlin in 1995. By that time – about a third of the way between the 1992 Earth Summit and the target year 2000 – the parties to the FCCC were pessimistic about the likelihood of meeting its goals, and decided that more stringent measures should be taken. They could not agree, however, on what these steps should be. What was created instead was the Berlin Mandate: a charge to the parties involved to negotiate, before the end of 1997, a set of international commitments to actions that went beyond what was more vaguely stated in the original FCCC. After many preliminary meetings, a second COP, and countless preliminary discussions, the parties met again in Kyoto, in December of 1997, at the third Conference of the Parties, COP-3, to negotiate the protocol that had been called for in the Berlin Mandate.

Carbon Dioxide:
The Road to Mitigation
Milestone Date Location Result
Earth Summit June 1992 Rio de Janeiro Framework Convention on Climate Change (FCCC)
First Conference of the Parties March 1995 Berlin Berlin Mandate

Second Conference
of the Parties

July 1996 Geneva Technical progress
Third Conference of the Parties December 1997 Kyoto Kyoto Protocol
Fourth Conference of the Parties November 1998 Buenos Aires Technical progress



The Kyoto Protocol

The Kyoto negotiations created a more specific framework for reducing, or mitigating, greenhouse gas emissions. Country-by-country emissions reductions, averaging 5.2 percent, were established as goals for the Annex I nations. Other definitions and clarifications were also included. It specified the six greenhouse gases – CO2, CH4, N2O, HFCs, PFCs, and SF6 – that were targeted for reduction, and bundled their climatic impacts together in terms of "CO2 equivalent emissions." It forestalled compliance for the stipulated Annex I reductions until a bounded period of commitment a decade in the future, from 2008 to 2012. To help control costs it established the principle of emissions trading for Annex I nations, a mechanism for actions implemented jointly, and a "Clean Development Mechanism," which could create emissions credits in participating non-Annex I nations.

The rules by which these principles will be implemented were left, however, for future negotiations. Like the Rio FCCC, the Kyoto Protocol established no penalties for non-compliance. And like the original FCCC, emission reduction goals were established for only a limited period, and with no reference to a specified ceiling in terms of global concentrations in parts per million.

Beyond Buenos Aires

Much work remains to be done in Bonn (when the Fifth Conference of the Parties will be held, in 1999) and at similar conferences to follow, if the principles of Kyoto are to be realized. The agreement framed in Kyoto will not become binding until the parties return to the United Nations with instruments of ratification. None of the major emitters, including the United States, has as yet ratified the agreement. Given concerns expressed in the U.S. Senate, which must ratify the Protocol if this country is to participate, the prospects for the agreement ever entering into force are as yet uncertain. But even if Kyoto's goals were fully met, it would still be no more than a start in terms of what is ultimately needed to stem the continuing increase in greenhouse gas concentrations.

To illustrate this point, we show in Figure 1 the potential effect of the Kyoto Protocol on first the amount of CO2 that is emitted, each year, and then on the resulting concentration, through the next 100 years, based on modeled calculations at Battelle. The black line in each of the two diagrams is an IPCC projection of possible future emissions and concentrations if no concerted action is taken to reduce them. The blue lines, in each case, show our calculations of how emissions and concentrations would be affected were the Annex I nations to abide by the Kyoto Protocol, with the further assumption that the Protocol – which establishes emissions objectives for only five years, 2008 to 2012 – is renewed to apply throughout the remaining eighty-eight years of the 21st century. In addition, we assume that the reductions in Annex I nations do not lead to any increases in the emissions in other countries: that is, reduced oil demand and reduced oil prices do nothing to stimulate fossil fuel use and emissions in non-Annex I nations. The "extended Kyoto Protocol," as we have defined it, cuts global emissions by roughly 15 percent – or about two and a half billion metric tons (called "tonnes," each equal to 2200 lbs) of carbon per year – by the end of the century. But despite the reductions on the part of Annex I nations, total global emissions continue to rise, about as steeply as before, throughout the period.

Concentrations will of course also be affected. By the end of the next century, in the year 2100, the amount of CO2 in the air drops about 50 ppmv below the unencumbered IPCC projection. But as with emissions, the concentration still continues to climb. Furthermore, the date when the concentration first exceeds 550 ppmv – a doubling of the pre-industrial value – is postponed by less than a decade.

It is clear that the Kyoto Protocol, even if extended throughout the next century, is highly unlikely to achieve the underlying goal of the FCCC.

Back to Basics

The relationship between the amount of CO2 we release each year and the eventual concentration in the air around us is not a simple one. Almost all of Nature has a hand in the game. Complex interactions among the air and oceans and soil and living things can both add to and subtract from the carbon we have added to the air. Some natural reservoirs, like the deep oceans, can absorb and hold carbon from the air for hundreds of thousands of years; others, like the trees, give much of it back in a matter of months. Almost all of these processes depend on the temperature, which is affected by the CO2 we emit, and some are affected directly by CO2 itself.

Workable strategies for stabilizing greenhouse gases in the atmosphere must nevertheless address both emissions and concentrations, and link them, reliably, to each other. Will negotiated emission reductions of certain amounts (as in the Kyoto Protocol) hold concentrations within a specified ceiling? What should that ceiling be, in ppmv? Are there efficient (i.e., least painful to all involved) emission paths to get there?

Some possible emission paths

Considerable effort has gone into developing emissions paths (or profiles) that are consistent with alternative concentration ceilings. But, despite the wide variety of paths that have been considered – immediate cutbacks on the part of all or some nations versus more tailored or tapered ones – all share a number of common characteristics. Any that endeavor to meet ceilings of 450 ppmv or higher allow global emissions to continue their present rise for some period before peaking and eventually turning downward.

Three of these possible emissions paths, and their resultant concentration ceilings, are shown in Figure 2, where they are also compared with the "business as usual" emission trajectory that was projected by the IPCC, and its modification by the (extended) Kyoto Pact. Table 1 uses the same emission profiles to illustrate how CO2 emissions would need to be reduced, and when, to remain within different concentration ceilings.

The Kyoto Protocol trajectory produces more than enough emissions reductions to satisfy the requirements, for a time, of all but the most stringent of the emission paths that are shown. However, to return CO2 concentrations to 350 ppmv – approximately the amount in the air in 1990 – more draconian measures are needed, for global (not just Annex I) emissions must begin to drop, and continue to drop rapidly toward zero, beginning a scant six years from now, in 2005. Relaxing the allowable ceiling to 450 ppmv forestalls that day by an additional six years, to 2011, when emissions must begin to decline. Were a doubled CO2 (550 ppmv) a tolerable ceiling, the (extended) Kyoto Protocol would suffice until about 2035, after which emissions must again begin to drop. But in that case the Protocol initially requires more emissions mitigation than is needed for that concentration ceiling, raising questions about the balance between costs and benefits, while ultimately proving inadequate to stabilize concentrations.

But in any of these cases, reversing the direction of the global emissions curve from upward to downward (in 2005, for example, to meet a 350 ppmv ceiling in global concentration) will never happen under the terms of the Kyoto Protocol alone. Achieving this historic turn of events will require substantial reductions in carbon emissions by both the major industrialized and industrializing countries, including the United States and other developed nations, as well as China, India, and Russia. Even if the emissions of Annex I nations were reduced to zero, which is a most unlikely scenario, it would forestall the necessity for substantial mitigation by non-Annex I countries for only forty years.

As we should expect, the 550-ppmv ceiling referred to in Figure 2 eases the task of emissions mitigation when compared to more stringent targets. The Kyoto Protocol is sufficient to keep global emissions within the bounds of the associated path until the about the year 2035. In fact, it provides more mitigation than is called for. But after the year 2035, simply renewing the Kyoto Protocol will not suffice. To stabilize the atmospheric concentration at 550 ppmv requires that after 2035, global emissions of CO2 must begin to decline.

If higher concentration ceilings, such as 650 or 750 ppmv (about double the present concentration), are considered, the required emissions mitigation is, of course, relaxed even more. In fact, if one believes that 650 ppmv or 750 ppmv were safe and responsible ceilings, then any of the cuts prescribed in the Kyoto Protocol would probably be premature. Ultimately, present actions must be based on a balance between potential risks associated with different concentration ceilings and the costs of different levels of stringency of mitigation.

The Fossil In Our Future

Energy is at the heart of the climate issue. Most of the carbon dioxide that our own activities add to the air comes from fossil fuels, which are the principal provider of energy services for the whole world. Without policy intervention things will likely continue that way, for fossil fuel energy is convenient, cheap, and abundant. Real U.S. oil prices (adjusted for inflation) were in 1998 at their lowest levels since the second World War. And energy use is growing rapidly, especially in developing nations.

The bad news is what is left behind when carbon fuels are burned. Global carbon emissions increase every year, with no obvious natural end in sight, for there is little if any chance that the world will run out of fossil fuels before global warming could become serious. Conventional oil and gas resources may indeed be limited, but they are not the major concern, for they make up but the "tip of the iceberg" in terms of the total fossil fuel inventory on the planet. Were we to burn all conventional oil and gas resources in the course of the 21st century, the global concentration of CO2 would not rise above 450 ppmv, and there would probably be no need for an IPCC, an FCCC, or this review in CONSEQUENCES. The real threat to future climate lies in the vast stores of other fossil fuels, and particularly coal and "unconventional" oil (such as shale) and gas. When coal and unconventional oil and gas are included, the global fossil fuel inventory is adequate to fuel the world's economies for centuries to come. And in the process, to load the atmosphere with enough carbon to drive CO2 concentrations to at least 1100 ppmv, or more than four times the pre-industrial level.

If the nations of the world are to keep CO2 from reaching a concentration above 750 ppmv, the long-rising trend in CO2 emissions must be made to peak and then decline sometime in the twenty-first century. But it is important to note that this need not require fossil fuel use to peak and decline in that period, if there were practical methods to limit the carbon that fossil fuels emit. The development of carbon capture and storage (or "sequestration") technology, for example, would allow a continued expansion of fossil fuel use, even as fossil fuel CO2 emissions declined.

Outside the technology box

Carbon capture and sequestration holds great promise as an additional tool for controlling carbon emissions and limiting the cost of large-scale emissions mitigation. Many methods are potentially available, including capture by "scrubbing," as is now done for sulfur, or removal and storage of carbon from the fuel before combustion; possible biological methods include storage in soils or plants. A wide range of repositories for long-term storage of carbon have been considered, including depleted oil and gas wells, coal seams, and the deep ocean. In all, the notion of capture and sequestration is more like a tool box than a single implement, and none of the tools in the set has been applied to a problem of comparable magnitude to the task which looms ahead.

A great deal more research is needed before any attempt at large scale application can be made. That research must answer such questions as: How permanent are potential storage repositories? Would the large scale sequestration of carbon cause other environmental problems? How expensive will these technologies prove to be? How do we solve technical problems for handling and storing commodities such as carbon and hydrogen? Answering these questions will be a daunting challenge for the biological, material, and engineering sciences.

Two facts make these technologies and their associated science particularly important. First, given the enormous emissions mitigation challenge that lies ahead in the second half of the next century, every available approach will be needed to control costs. And second, these technologies, and particularly those associated with the biological sciences, offer the only hope presently available, nascent as it is, for lowering the concentration of CO2 in the atmosphere, should that prove necessary.

Technology Futures

The steeply-increasing carbon emissions that are projected for the future by the IPCC (as shown in Figures 1 and 2) are commonly used in economic studies and projections. They are also predicated on a wide range of assumptions, not the least of which are those concerning future energy technology. Among these technology assumptions are significant improvements in energy efficiency.


For example, the IPCC assumes that 100 years from now, renewable and nuclear energy technologies will have improved to the point where they provide more than 75 percent of all electric power, compared with but 24 percent (mostly from nuclear and hydroelectric generation) in 1990. In addition, in the same time span the scale of non-carbon technologies – such as biomass, nuclear, solar, and wind power – is assumed to grow to almost twice the size of the entire global energy system in 1990. End-use energy technologies also improve. Energy consumed per unit of economic activity declines to 1/3 of 1990 levels.

Needless to say, these assumptions pose a large technological challenge.

For purposes of illustration, we have recalculated the IPCC projections of future CO2 emissions under the assumption that the world’s average energy technology does not advance beyond 1990 levels. Such a turn of events is hardly possible, but it allows us to see more clearly the amount of technological change that is assumed in the IPCC reference case.

The heavy reliance that was placed on presumed technological advances is evident in Figure 3, for both emissions and atmospheric concentrations of CO2. Even with these presumed advances, however, the IPCC projection leads to an atmospheric concentration in the year 2100 of more than 700 ppmv, which is two and a half times the pre-industrial level of about 275 ppmv.

If we are to stabilize the amount of CO2 in the air, the world's energy system will need to shift more deliberately to non-carbon-emitting technologies. A transition from the present carbon-emitting energy technology to an alternative non-carbon technology will entail costs. The degree of sacrifice – that is, the cost of carbon emissions mitigation – will depend primarily on five factors:

1. The permitted ceiling for global CO2 concentration;

2. The extent of participation among the world’s nations;

3. The degree of flexibility as to where and when net emissions mitigation can be undertaken;

4. The non-carbon-emitting-technology alternatives that become available; and

5. The availability of carbon sinks and carbon-removing technology.

Each of these factors can exert a truly profound effect on the cost to the world of stabilizing the amount of carbon in the atmosphere.

Minimizing costs is particularly important. When the costs of reducing carbon emissions are perceived to be high, responsible actions are almost inevitably delayed – and particularly so when the threat that is posed lies in the future. Higher costs mean diverting more resources from other worthy goals, such as improving health, providing education, reversing the effects of past pollution, and raising the material standard of living.

Policy, Technology, and Cost

If the concentration of greenhouse gases is to be stabilized, there are at least two pre-conditions that must be met. The first is a credible commitment to a future (in terms of energy usage) that is different from the past. The second is a strategy for controlling the costs of making so profound a change. If either of these fails to come about, controlling the amount of carbon in the air will prove impossible.

The need for a policy commitment

In the absence of a widely accepted policy that the unrestrained release of carbon to the atmosphere can no longer be allowed, and that global net CO2 emissions (that is, the difference between what is added to the air and what it soon loses) must eventually decline — nothing will happen. Nor can the market alone be counted on to bring these goals about. A technology strategy which works on the presumption that market forces are capable, by themselves, of carrying us into a bright new carbon-free energy future ignores the fact that climate is an un-priced commodity. As such, its value can never be fully incorporated in the marketplace.

The form of that commitment remains for the future to disclose. It may grow out of an expanded and extended Kyoto protocol, or it may require new political and institutional mechanisms. But, whatever the form, a policy commitment – one that engages all of the major emitting nations of the world, one that controls costs, and one that is structured to encompass the long-term nature of climate change – is an essential element in "solving" the climate problem.

This is not to say that the encouragement of advanced, non-carbon, energy technology development will not help to reduce the growth of CO2 emissions. Or that technological change cannot benefit both the production and consumption of fossil and non-fossil fuels. But unless we find and harness non-carbon emitting energy technologies (that are also cost competitive) at a faster rate than reference scenarios assume, carbon emissions will not peak, and we will not be able to stabilize their concentration in the atmosphere. These reference scenarios, moreover, tend to be optimistic.

Similarly, policy alone will not be enough. A policy which controls emissions without controlling costs, cannot be sustained.

Controlling the costs of mitigation

Global greenhouse warming is a long term problem and thus an intergenerational one. Our own actions, and those of our predecessors, around the world, have set natural processes in motion that will inexorably alter the climate in which we and our descendants will live.

Nor are there any quick ways currently available to erase what we have done. The degree to which we can alter the concentration of CO2 in the air is highly limited, over even a decade. It will take many tens of years to make any significant change. Thus, the actions we take this year, or next, to help solve the problem will affect our descendants far more than ourselves, and maybe not ourselves at all. The mitigation of carbon emissions calls largely on altruism. And, while there is ample evidence of altruism in the world, it is ever in short supply, given the other worthy causes that call for our attention and sacrifice.

The hope of improved energy technology

Technology is a major determinant of mitigation costs. Depending on which technologies become available – and particularly in the next twenty-five years – the minimum cost of stabilizing CO2 in the atmosphere can vary by literally trillions of dollars – by more than the annual gross domestic product of the U.S.A.

We can explore how energy technology might affect the costs of stabilizing CO2 by applying two different assumptions about technology to the projections of the IPCC. These are:

1.  1990 Technology—Technologies are frozen at 1990 levels. No energy technology improvements are allowed, but other assumptions used by the IPCC regarding population and economic growth, energy resource availability, and the cost of energy supply are unchanged.

2.  Reference Technological Progress—This is the reference adopted by the IPCC in making their projections of likely CO2 emissions, in which technology proceeds briskly, but incrementally. Significant energy technology improvements are assumed, in both fossil and non-fossil energy technologies, over the course of the coming century. Renewable energy forms, such as hydro, biomass, solar and wind power, become cost competitive and replace fossil fuels as the dominant mode of electric power generation by the year 2100. Nuclear power technology is cost effective and utilized globally. End-use energy applications improve at the rate of one percent per year on average, reducing the demand for energy service in the year 2100 by two thirds from what it would have been with 1990 technologies. It is this set of technological change assumptions which in Figure 3 leads to a CO2 concentration of more than 700 ppmv.

Each of these two technology regimes, were all else the same, would result in a different CO2 emissions profile. But to stabilize CO2 in the atmosphere, however, would require, in addition, an assumed policy mechanism.

For purposes of illustration, and to get an idea of the minimum costs involved in either of the two technology options, we assume that mitigation is undertaken wherever and whenever it is cheapest to do so. For the moment we will ignore how this ideal might be realized, although a global carbon tax regime or a global allocation of tradable emission permits would help in this regard. The real world, of course, will never deliver a minimum cost solution. A multitude of different inefficient policy regimes are possible, and each has its own, quite-different cost. Since we have no way of predicting which road the world will ultimately follow, we shall use, for our purposes here, the single, cost-effective one and take it as a point of reference.

The value of technology

In Figure 4 we compare the costs of stabilizing the atmosphere at four different concentrations – 450, 550, 650, and 750 ppmv of CO2 – based on the global emissions trajectories shown in Table 1 and Figure 2, under the two technology assumptions that were described above.

For the reasons noted earlier, the cost estimates shown in Figure 4 should be seen as a lower bound on what would be experienced in reality. But the patterns are revealing. The costs of stabilizing the concentration at 550 ppmv with 1990 Technologies and with IPCC Reference Technological Progress differ by 1200 percent, or eleven trillion dollars. This is more than 2 percent of the world’s Gross Domestic Product for the next century, and more than the total amount that developed nations spend on all other forms of environmental compliance.

Technology lowers costs by reducing the amount that fossil fuel emissions needs to be cut back. Technology makes policy more powerful, because it reduces the required level of sacrifice. And while different economic models, even with the same technology and policy assumptions, yield different estimates of costs, they all confirm the overarching importance of energy technology in fixing the price of meeting any CO2 concentration ceiling.

Toward A Strategy

As we have said before, stabilizing the concentration of greenhouse gases will not be possible without (1) a clear commitment by most of the world's major emitting nations that the future will be different than the past – that is, that emissions will eventually decline; and (2) the development of satisfactory mechanisms for controlling costs. For a given technology, the nature of policy instruments that are applied has a major influence on the actual cost of channeling future energy developments. But the choice of technology has an equally strong influence on the potential cost.

As negotiators meet in future UN Conferences of the Parties, controlling the cost of emissions mitigation will continue to be one of the major challenges confronting them. Identifying a mechanism that would support the needed research and encourage and expedite the development and deployment of technology to limit carbon emissions and remove carbon from the atmosphere could make that task far simpler.

It will not be easy. Expenditures on energy research and development, around the world, have been in decline for more than a decade. In the U.S. they have fallen to the point where a fee of one dollar per tonne of carbon emitted – which amounts to only a quarter of a cent per gallon of gasoline at the pump – would raise enough revenue to increase energy research and development by fully 50 percent.

While technology has not been a major feature of the existing negotiations, it could be a major part of the solution to the climate change problem. Finding a way to accelerate the development and deployment of new technologies may not sound glamorous or heroic, but it could change the whole complexion of the carbon and climate dilemma.

What are the incentives for investing more, and trying harder? We need remember that finding a way to develop a robust energy and carbon technology strategy could be worth not millions, or billions, but trillions of dollars in addressing what may prove to be the central environmental problem of the twenty-first century.



Dr. M. Granger Morgan is Head of the Department of Engineering and Public Policy at Carnegie-Mellon University in Pittsburgh, where he holds the Lord Chair Professorship in Engineering. Much of his research involves studies of the human dimensions of global change.

Dr. Thomas Schelling is Professor of Political Economy, emeritus, Harvard University and Distinguished University Professor at the University of Maryland in College Park. He was president of the American Economic Association in 1991, and is a member of the National Academy of Sciences.

Dr. John Weyant is Professor of Engineering-Economic Systems and Operations Research at Stanford University, and Director of the Stanford Energy Modeling Forum. He has also served as a convening lead author for the second and third assessments of the Intergovernmental Panel on Climate Change.


For Further Reading

Climate Change 1995: Economic and Social Dimensions of Climate Change. The Contribution of Working Group III to the Second Assessment Report of the Intergovernmental Panel on Climate Change. Intergovernmental Panel on Climate Change Edited by J. P. Bruce, H. Lee, and E. F. Haites. Cambridge University Press, Cambridge, England, 1996.

Climate Change 1995: The Science of Climate Change. Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, England, 1996. Summary available on the Internet at

Primer on Greenhouse Gases, by D. J. Wuebbles and J. Edmonds. Lewis Publishers, Chelsea, MI., 1991.

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