Global Climate Change Briefing Book
Congressional Research Service
Redistributed as a service of the National Library for the Environment

John R. Justus and Susan R. Fletcher

The Issue

Scientists have discovered that changes in the Earth's climate and biosphere might be induced by the increasing concentrations of certain gases that are now measurable in the Earth's atmosphere -- some naturally occurring, others man-made -- that have the potential to significantly alter the planet's heat and radiation balance. Popularly termed "global warming," an increase has been measured in average global temperatures of approximately 0.9 degrees Fahrenheit over the past century. If current trends continue, the latest projections for future warming have been increased to between 2.7 and 10.8 degrees Fahrenheit over the next century.

Included among these "greenhouse" gases are carbon dioxide, methane, and nitrous oxide, as well as several other gases occurring in trace amounts in the atmosphere. Such alterations of Earth's heat and radiation balance could lead to an increasingly warmer climate in the next century, portending a potpourri of possible effects -- both potentially adverse and beneficial -- for human health and welfare and for the land and aquatic biospheres. As the ramifications of those developments become better understood, and given what scientists are currently able to tell planners and policymakers about the magnitude, timing, rate, and regional consequences of any potential climatic change, the key issues include questions of what are the appropriate policy responses both at the national and international levels. (For more information, see CRS Issue Brief IB89005: Global Climate Change. [pdf 8/13/01] [html 4/11/01)


It is now widely accepted by the scientific community that human activities, such as the burning of fossil fuels, deforestation, and certain land-use practices, are increasing atmospheric concentrations of carbon dioxide (CO2), which, along with increasing concentrations of other trace gases (methane, nitrous oxide, hydrofluorocarbons-HFCs, perfluorinated compounds-PFCs, sulfur hexafluoride-SF6, and trifluoromethyl sulfur pentafluoride-SF5CF3), could affect global climate. Careful monitoring and direct measurement of the concentrations of those gases in the atmosphere, and analysis of ice cores in Greenland and Antarctica that have captured past concentrations of some of those gases, leave no doubt that their global concentrations are increasing. Emissions of CO2 and the other greenhouse gases are not regarded as criteria pollutants (e.g., carbon monoxide, nitrogen oxides, volatile organic compounds, ozone, particulate matter) in terms of direct effects on human health and, therefore, have not been regulated directly in such pollution control laws as the Clean Air Act. In addition, they are emitted by most major productive activities in human societies -- transportation, use of power to heat and cool buildings, industrial activity, etc. Their pervasive nature makes limitations seem potentially restrictive in all these areas. Any specific emissions limits are shaping up to be very controversial.

According to recent projections based on computer models of the atmosphere, if these gases continue to accumulate, a globally averaged warming of 2.7 to 10.8 degrees F could occur over the next 100 years through enhancement of Earth's naturally occurring "greenhouse effect" -- the process by which the atmosphere traps infrared radiation emitted by the Earth, warming the Earth's surface in a process somewhat analogous to that which occurs in a greenhouse. The potential for impacts of such a climate change -- some positive, some negative -- on natural systems, national economies, and quality of life is uncertain and the subject of intense investigation. Thus far, scientific evidence suggests that, in some regions of the world, climate change could be detrimental for human health, ecosystems, food security, and water resources.

Globally averaged air temperatures at the Earth's surface have warmed by about 0.9 degrees F over the last 100 years. Natural variability of climate is large enough, however, that even the record-setting warmth of some years in the 1980s and 1990s or singular events such as a severe summer drought or seasonal flooding have not allowed a majority of scientists to state with any certainty that a global warming signal attributable to human activities has been identified . . . at least not until now. The Intergovernmental Panel on Climate Change (IPCC), jointly established in 1988 by the United Nations World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), reported in its Second Assessment (1996) that ". . . [such] a change is unlikely to be entirely natural in origin . . . [and that] the balance of evidence, from changes in global mean surface air temperature and from changes in geographical, seasonal, and vertical patterns of atmospheric temperature, suggests a discernible human influence on global climate." And now, the latest report (January 2001), the Intergovernmental Panel's Third Assessment, concedes that a firmer association between human activities and climate seems to have emerged. That is news, because reservations about the source of the past century's warming and whether it bore a human fingerprint are often cited in policy debates, usually in support of deferring actions aimed at mitigating possible global warming. In addition, the IPCC reports a higher range of potential warming - roughly between 3 and 11 degrees Fahrenheit over the next 100 years.

The so-called "global warming" theories and the IPCC findings have not gone unchallenged, however, within the scientific community. Critics argue that scientific proof supporting scenarios of future global warming is incomplete, and that many uncertainties remain surrounding the nature and direction of Earth's climate itself -- including the timing, rate, magnitude, and extent of any model-projected global warming. They question the ability of the atmospheric simulation models to project accurately a future global warming when computer runs using those same models yield more warming over the past 100 years than has actually been measured at the Earth's surface. They point to satellite instruments, which indirectly measure the conditions of the atmosphere in a vertical column of air well above the Earth's surface. Interpretation of the data record from those satellite instruments shows little or no positive global warming trend over 21 years (1979-1999) of record. Still others question whether the roles of such natural drivers and governing factors of climate as the Sun, and its various solar cycles, the world ocean, or the land and aquatic biospheres are properly accounted for in simulations of climate, past and present. Continued research is indicated if such questions are to be answered and if unknowns and uncertainties are to be reduced. In this regard, the IPCC is currently in the final stages of producing what will be its Third Assessment Report, scheduled for release in early 2001. (For further information see Greenhouse Effect and Global Climate Change in this Briefing Book.)

International political implications have proven significant. By far the majority of greenhouse gases are emitted by sources in industrial and transportation sectors (especially automobiles) that are concentrated in developed countries. Those countries have shown concern not only about their own emissions, but about increased emissions from poorer countries as they expand their economies. Friction has been evident in the debates over which actions, by developed and developing countries should be undertaken, on what schedules, and which parties should pay incremental costs for mitigation measures. Developing countries generally have argued that the financial burden of change should be borne by developed countries, which are mainly responsible for current atmospheric change due to human activity.

The nations of the world have been meeting annually under the auspices of the United Nations Convention on Climate Change, and at Kyoto, Japan, in December 1997 agreed on legally binding reductions in greenhouse gas emissions for the most developed nations. The United States signed the Kyoto Protocol on November 12, 1998, but the Clinton Administration did not submit it to the Senate for advice and consent, citing the lack of developing country participation in the commitments to limit greenhouse gas emissions, which the Senate had indicated in S.Res. 98 would be necessary for its approval for ratification. As of November 2000, some 84 nations had signed the Protocol, and 31 had ratified. None of the industrial nations with binding reduction commitments have ratified the Protocol. Without these ratifications the Protocol will not enter into force. (For more information on the background of the Protocol and recent negotiations, see CRS Report RL30692, Global Climate Change: The Kyoto Protocol.[pdf: 8/13/01] [html: 4/11/01)

Technical work has been progressing on many of the methodologies and procedures needed to implement the Convention and to ensure that the Protocol would be fully operational at such time as it might enter into force: A number of specifics relating to commitments, emissions trading mechanisms, implementation, compliance, and enforcement of the Protocol remain to be clarified and finalized. It was a goal of the parties that these issues would be resolved by the sixth conference of the parties (COP-6), held in The Hague, November 13-25. However, these negotiations collapsed without agreement due to major political differences, especially among the developed countries, in addition to the technical difficulties in getting agreement on how to make the Protocol's mechanisms operational. The Bush Administration asked for a delay in resumption of these negotiations, to allow time for consideration of its approach and policies, and talks are now likely to be scheduled for the second half of July.

Several committees of relevant jurisdiction in the House and the Senate held hearings in the 106th Congress, reviewing the details of the Kyoto Protocol and related issues. In that milieu, arguments were presented that policy actions to reduce emissions of carbon dioxide and other greenhouse gases should be taken now, in line with the intent of the Kyoto Protocol. Alternative arguments called for delay, citing scientific uncertainty, the need to expand technological options for mitigating or adapting to the effects of any climate change, and the associated high cost of replacing capital stock before the end of its economic life. Of particular interest was whether enacting measures that would focus on carbon dioxide and other greenhouse gas reductions to meet the terms of the Protocol could be achieved at little or no net cost to the national economy, as some have suggested, or whether the Protocol might result in increased taxes, loss of jobs, or a dramatic jump in energy costs for Americans, as others have suggested. (See Energy Issues and Economic Issues in this briefing book). Other questions related to whether any environmental benefit at all would be achieved under the levels of greenhouse gas reductions mandated by the Protocol. Those committees also engaged in examining the details of federal spending initiatives related to climate change research, technology investments, and tax incentives with an eye toward determining first, if they were worth the money, and second, what portion of that spending might constitute sound contingency actions to deal with the potential of global climate change versus what portion might prematurely commit the United States to the as yet unratified Kyoto Protocol.

Debate in Congress over the prospect of global warming, to the extent it occurs, and what the United States could or should do about it, has produced legislation in the years since the Kyoto Protocol was agreed in 1997 from both sides of the issue (see Legislation in this Briefing Book), including a number of proposals aimed at finding ways to give credit to activities that lower greenhouse gas emissions, even if the Kyoto Protocol is not finally approved, and provisions in several appropriations bills to prohibit funding for activities to implement the Kyoto Protocol prior to its ratification by the United States.

Domestically, environmental groups welcome the Kyoto Protocol, but many industrial and labor groups either oppose it or argue for major modifications. The Protocol would require the United States to reduce greenhouse gas emissions -- mostly carbon dioxide -- by 7% from 1990 levels, on average, in the period 2008-2012. Language in the Protocol does allow for the conduct of emissions trading and joint implementation, although details for such are left to be fleshed out by the annual meetings of the Conference of the Parties to the Framework Convention. The Protocol does not, however, contain any new commitments for developing countries, as called for by the President in October 1997 and set by the Senate in S.Res. 98, passed 95-0 on July 25, 1997. That resolution also expressed Senate opposition to any protocol whose binding provisions would seriously harm the U.S. economy or were not backed by sound scientific and economic analysis

It is likely that the debate over whether the Kyoto Protocol is the appropriate mechanism to address climate change concerns will continue, within Congress and in public opinion, and that additional research will provide further insights into the science of climate change, adding new perspectives to this debate.

Page last updated March 8, 2001.

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