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Testimony before Committee on Science - March 6, 1996

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Statement of
Dr. Robert T. Watson
Associate Director for Environment
Office of Science and Technology Policy
Executive Office of the President
before the
Committee on Science
United States House of Representatives
March 6, 1996

Mr. Chairman and Members of the Committee:

I greatly appreciate being given the opportunity to discuss global climate change with you and your subcommittee. I am the Associate Director of the Environment Division in the White House Office of Science and Technology Policy. The Administration believes that this is an extremely important environmental issue of profound importance to this and future generations.

My testimony on the scientific knowledge of climate change is based on the latest findings of the Intergovernmental Panel on Climate Change (IPCC) Assessment, conducted under the auspices of World Meteorological Organization (WMO) and United Nations Environment Programme (UNEP). I will discuss the U.S. Global Change Research Program (USGCRP) within the context of this international scientific consensus.

The IPCC reports were prepared by over five hundred authors and reviewed by over one thousand scientists from universities, government laboratories, industry, and other private sector organizations from developed and developing countries. They were subjected to both an "expert" review and an in-depth governmental review. The three Summaries for Policymakers and the Synthesis report, were ultimately approved line-by-line by governments and technical experts.

Two other international assessments, the UNEP Global Biodiversity Assessment, and the UNEP-WMO Stratospheric Ozone Depletion Assessment also provide a sound scientific basis for elements of the USGCRP, given the inter-relationship between these different issues.

Scope and Importance of the Climate Change Issue

While climate change is inherently a global issue, it is critical that we understand how climate will change at the regional scale and what the potential consequences may be. To be specific, we need to know how climate will change in the United States, what the consequences will be in different regions, and whether there are cost-effective solutions to slow climate change or adapt to it. Therefore, the scope of a comprehensive climate change research program should evaluate:

  • how human activities affect regional and global climate;
  • what the potential consequences of climate change are; and
  • the options for mitigation and/or adaption to climate change.

Current Understanding of Climate Change

The large majority of scientific experts have concluded, based on empirical evidence and simulations, that human activities have already affected the Earth's climate and that further human-induced climate change is inevitable. While a number of key scientific uncertainties remain, for the first time, the scientific community through the IPCC has stated "there is a discernible human influence on global climate." In other words, the question is not whether climate will change in response to human activities, but rather where (regional patterns), when (the rate of change) and by how much (magnitude).

It is also clear that climate change will, in many regions, adversely affect human health, ecological systems, and socio-economic sectors, including agriculture, forestry, fisheries, water resources, and human settlements. The good news is, however, that significant reductions in greenhouse gas emissions are technically feasible due to an extensive array of technologies and policy measures in the energy supply and energy demand sectors at little net cost to the economy. Such measures can slow climate change, but will require concerted R&D and demonstration to have these technologies penetrate the marketplace domestically or worldwide.

The following section summarizes the main IPCC conclusions for each of the three questions.

1. How do human activities affect regional and global climate?

Our ability to predict changes in climate at the regional level remains low, however we do know that:

  • Human activities are increasing the atmospheric concentrations of greenhouse gases -- which tend to warm the atmosphere, and in some regions, aerosols -- which tend to cool the atmosphere;
  • The Earth's climate is changing: the surface temperature this century is as warm or warmer than any other century since 1400 AD; the Earth's surface temperature has increased by about half a degree centigrade over the last century; and the last few decades have been the hottest this century;
  • The balance of evidence suggests a discernible human influence on the Earth's climate;
  • Models that take into account the observed increases in the atmospheric concentrations of greenhouse gases and sulfate aerosols simulate the observed changes in both surface temperature and its vertical distribution quite well;
  • In addition to changes in surface temperature, sea level is projected to increase by 15-95 cm by 2100, glaciers are retreating world-wide, and the incidence of extreme weather events is increasing in some parts of the world. Even with a stabilization of greenhouse gas concentrations in the year 2100, temperature would continue to increase for several decades, and sea level would continue to rise for centuries;
  • The atmospheric lifetime of many greenhouse gases, coupled with the thermal inertia of the oceans, means that the warming effect of anthropogenic emissions will be long-lived -- even sharp reductions in greenhouse gas emissions would reverse warming very slowly; and
  • Without global climate specific policies to mitigate greenhouse gas emissions, the Earth's temperature is projected to increase by between 0.8 to 3.5 degrees Centigrade by 2100: a rate faster than anything observed during the last 10,000 years; higher latitudes are expected to warm even more.

2. What are the potential consequences of climate change?

  • Regional and global changes in temperature, precipitation, soil moisture, and sea level are expected to have wide-ranging and potentially adverse effects on physical and ecological systems, human health and socio-economic sectors, thus affecting the economy and the quality of life for this and future generations;
  • Human-induced climate change is an important new stress, particularly on ecological and socio-economic systems that are already affected by pollution, increasing resource demands, and non-sustainable management practices;
  • Most systems (human health, ecological and socio-economic systems) are sensitive to both the magnitude and rate of climate change;
  • While impacts of climate change are hard to quantify because of uncertainties in regional climate projections, the fact that systems are subject to multiple stresses, and incomplete understanding of some key processes, we can project significant, often adverse affects on:
    - human health: there may be an increase in heat-related mortality, vector-borne diseases such as malaria, dengue, yellow fever, and encephalitis, and non-vector-borne diseases such as cholera and salmonellosis;
    - food security: significant regional dislocations could occur especially in the tropics and subtropics, where many of the world's poorest people live; even though the effect of climate change on overall global food production may be small to moderate;
    - natural ecosystems: the composition, geographic distribution and productivity of many ecosystems will shift as individual species respond to changes in climate. There will likely be reductions in biological diversity and in the goods and services ecosystems provide to society. For example, climate change is expected to occur at a rapid rate relative to the speed at which forest species grow, reproduce and re-establish themselves. Therefore, species composition of forests is likely to change, entire forest types may disappear, and new assemblages of species and hence new forest ecosystems may be established. Between one-third and two-thirds of vegetation types in forests are expected to change in response to a doubled-carbon dioxide climate;
    - human habitat loss: small islands and delta areas are particularly vulnerable to sea level rise. A one-meter sea level rise is projected to result in land losses ranging from as little as 0.05% in Uruguay, to 1.0% for Egypt, 6% for Netherlands, 17.5% for Bangladesh, and to about 80% of the Marshall Islands. Large numbers of people will be affected, e.g., tens of millions of people in both China and Bangladesh.

In some cases, such as species loss, the impacts of climate change are irreversible. Developing countries are more vulnerable than developed countries to climate change because of their socio-economic conditions.

3. Are there technically feasible and cost-effective options to mitigate or adapt to climate change?

  • Stabilization of the atmospheric concentrations of carbon dioxide at any level at, or below, three times pre-industrial levels will eventually require global emissions to drop below today's levels;
  • Significant "no-regrets" opportunities, these which make sense for other reasons in addition to climate change, are available in most countries to reduce net greenhouse gas emissions. Furthermore, the risk of aggregate net damage due to climate change, consideration of risk aversion, and the precautionary principle provides rationale for actions beyond "no regrets;"
  • A range of cost-effective technologies and policies can be used in both developed and developing countries to markedly reduce the net emissions of greenhouse gases from industrial, energy supply, energy demand, and land management practices. Projected greenhouse gas emissions can be reduced by 10-30% using current technologies over the next two to three decades at little cost;
  • It is technically possible to realize deep emissions reductions in the energy supply sector in step with the normal timing of investments to replace infrastructure and equipment as it wears out or becomes obsolete; and
  • Successful adaptation depends upon technological advances, institutional arrangements, availability of financing, technology transfer and information exchange;
  • Climate change concerns must be incorporated into resource-use and development decisions.
  • Flexible, cost-effective policies relying on economic incentives and instruments, as well as coordinated instruments, can considerably reduce mitigation and adaptation costs.

Research Priorities Related to Climate Change

This section will highlight some of the highest priority areas of research for each of the three major areas/questions discussed above.

1. What is the impact of human activities on regional and global climate in the context of natural climate variability?

There are a number of major challenges facing the scientific community if we are to improve our ability to predict future changes in regional and global climate. We need to:

  • develop more accurate projections, by sector and region, of future emissions of greenhouse gases in order to improve our projections of their future atmospheric concentrations, and subsequent warming;
  • conduct further research on the carbon cycle in order to more accurately quantify the atmospheric lifetime and future atmospheric concentrations of carbon dioxide, hence improving our projections of additional warming;
  • extend our understanding of the past, current and future distribution of aerosols and their radiative properties, hence develop projections of regional impacts;
  • improve our understanding of the response of the climate system, regionally and globally to additional radiative forcing, with emphasis on water vapor and clouds, and the exchange of energy between the atmosphere and oceans;
  • develop more reliable transient ocean-atmosphere climate models in order to quantify the rate and regional distribution of climate change, and the future location, severity, and frequency of extreme events;
  • continue to quantify natural variations and long-term trends in climate variables on a variety of spatial and temporal scales using the paleoclimatic record and a variety of space and non-space observational techniques;
  • continue to combine observations and models to establish the cause of long-term trends in climate variables.

2. What are the potential consequences of climate change?

To gain an improved understanding of the potential consequences of climate change, in the context of other stresses, will require a significant improvement in our ability to predict climate change at the regional level (including the location, severity, and frequency of extreme events), an improved understanding of key processes (including ecological, social, and economic), and an improved understanding of other stress factors such as air and water pollution, the demand for natural resources, and unsustainable management practices. We need to:

  • Improve our understanding of the response of ecosystems (distribution, function and composition) to changes in temperature, water availability, and atmospheric composition (e.g., carbon dioxide).
    More specifically:
    - How will ecosystem functions such as purifying and storing water, regulating water runoff, controlling coastal erosion, and regulating climate be affected by climate change?
    - At what rate can species re-establish themselves in new locations as climatic conditions change, and can human interventions be developed to assist this process?
    - How will increased levels of atmospheric carbon dioxide -- which has been shown to increase growth of some important plant species under laboratory conditions -- affect whole ecosystems over long periods of time?

  • Investigate how global change will affect employment opportunities, economic growth, national and international trade flows, and other social and economic characteristics that support the communities which make up the fabric of U.S. society.
    In particular, we need to understand how:
    - Agricultural and forest productivity will be affected by changes in climate and atmospheric composition, taking into account changes in the ranges and incidence of pests, the costs of adjusting cropping and forestry systems so that they are optimized with respect to new conditions, and the opportunities for growing new crops and changing land use;
    - Water resources will be affected by changes in temperature and precipitation; how these will affect the ability of water resource managers to cope with increased demand for freshwater, and the implications for planning and construction of water catchment and storage systems;
    - Climate change and sea-level rise will affect coastal systems, including commercial fisheries and buildings, and other infrastructure located in vulnerable coastal regions;
    - Changes in extreme weather events will affect the insurance and financial insurance industry; and
    - Changes in climate will affect human health, in particular how the range of vector- and non-vector-borne diseases will change in response to changes in climate variables.

3. Are there technically feasible and cost-effective options to mitigate or adapt to climate change?

Assessing the technical feasibility and cost-effectiveness of options to mitigate or adapt to climate change will require an evaluation of the technical potential of mitigation technologies, their cost-effectiveness, and the barriers to the diffusion of these technologies into the market place for each of the key sectors including: energy supply (including fossil, renewables, and nuclear); energy demand (including transportation, buildings, industry and utilities); and land-use practices (including carbon sequestration in vegetation and soils in rangelands, agriculture and forests). This will require emphasis on:

  • The development of improved technologies, including;
    - more efficient end-use energy technologies in all sectors, including transportation, buildings and industry;
    - non-greenhouse gas emitting supply-side technologies including nuclear and renewable energy technologies, especially biomass, solar thermal and electricity, wind and micro-hydropower; and
    - more efficient conversion of fossil fuels.
  • Understanding the major constraints which limit the commercialization of emerging "cleaner" technologies, and identification of the opportunities that can be used to overcome them;
  • Understanding the potential to reduce emissions and increase storage of carbon in grasslands and in the agriculture and forestry sectors, taking into account the relative benefits and costs of reducing net emissions by changing agricultural practices or establishing new forests.

Scope of the U.S. Global Change Research Program and Related Programs

The U.S. Global Change Research Program (USGCRP), which has a broader scope than global climate change, is a critical tool in addressing the uncertainties discussed above. It is designed to address a number of highly inter-related global environmental issues, including global climate change, seasonal to inter-annual climate fluctuations, stratospheric ozone depletion, changes in tropospheric chemistry, and land-use/land-cover changes. In addition, the USGCRP is closely coordinated with other research programs that study related environmental issues such as biological diversity, resource use and management, air quality, water resources, and natural disasters. This coordination is achieved through the Committee on Environment and Natural Resources (CENR) of the National Science and Technology Council (NSTC).

Importance of the Federal Government Role in USGCRP

Significant progress in understanding global climate change (and the other global environmental issues as mentioned above) has been made over the past decade or so because of the strong bipartisan commitment to the USGCRP. This was a program initiated by President Reagan and further developed by President Bush and Clinton with strong support from Congress. All three Administrations and Congress recognized the social and economic importance of the global environmental issues encompassed by the USGCRP. There was general agreement that enhanced scientific understanding is essential for the development of appropriate, cost-effective options to mitigate or adapt to climate change, ensure environmental protection, protect the health of our citizens, and ensure that economic and national security are not jeopardized.

The Federal government, in conjunction with the private sector should, and must, continue its commitment to a better understanding of our global environment. While the private sector has some limited research capability in the area of climate change, only the Federal government, in strong collaboration with its colleagues in academia, can adequately address the breadth of this critically important social issue.

Effective international cooperation is needed as well. The USGCRP provided most of the critical scientific information needed to develop national and international policies for safeguarding the Earth's protective ozone layer. Only a well-funded, scientifically-based USGCRP can provide the enhanced scientific and technical information needed to guide effective policy formulation for coping with climate change.

Implication for the Current USGCRP

The USGCRP is a well designed scientific program that is providing high quality policy-relevant information. During the last decade or so the program has made a large number of significant scientific advances and demonstrated flexibility in responding to new scientific challenges. Let me provide just two examples of scientific progress and programmatic responsiveness -- there are dozens more:

  • In response to the discovery of the spring-time Antarctic ozone hole, USGCRP agencies (NASA, NOAA and NSF) established a coordinated program of laboratory studies, theoretical modeling activities and observational programs (ground-based, balloon, aircraft, and satellite) to study this phenomenon. Within three years of its discovery the USGCRP had established its cause: long-lived industrially produced chlorine- and bromine-containing chemicals. It also established the cause of the mid- and high-latitude loss of stratospheric ozone, and quantified the impact of stratospheric ozone depletion on the Earth's climate.
  • In response to the 1990 IPCC Assessment Report which highlighted the potential importance of sulfate aerosols, several USGCRP agencies established research programs to better understand the role of aerosols in the Earth's climate. While key uncertainties still remain, these programs have led to a considerable improvement in our understanding and important convergence between observations and model simulations.

The scope and balance of activities in the USGCRP will need to continue to evolve in the future just as they have in the past. This program must, and does, devote significant resources to space and in situ observations and data management in addition to process studies, modelling and analysis. To understand climate change, both natural and anthropogenic, USGCRP will have to place an increasing emphasis on understanding the consequences of climate change at the regional level and on some key socio-economic aspects, including the costs and benefits of reducing greenhouse gas emissions. To perform such an analysis will require, among others, improved techniques to value biological resources and biodiversity, both in terms of market and non-market value, and understanding barriers to the diffusion of technologies into the market place.

We need to maintain the high quality science-driven USGCRP that emerged during the Reagan and Bush Administrations and which has been strongly supported by the Clinton Administration. The need to observe, understand and predict the Earth system has been given even greater emphasis by the latest set of findings from the IPCC. In particular, we need to improve our ability to predict climate change at the regional level, and we need an increased emphasis on understanding the consequences of climate change. The latter will require more research into basic ecological processes, development of more sophisticated modeling frameworks, and the establishment of improved capabilities for ground- and space-based monitoring and data management. In addition, we need better databases for vulnerability assessment and planning of adaptation, including data on population trends, resource utilization, and the value of natural and economic resources. The development of a broad range of sectoral and integrated modeling capabilities is also required to determine the potential significance of global change for the United States and the world.


The scientists of the world have agreed that climate is changing and that there is a discernible human influence. However, policymakers are faced with responding to the risks posed by anthropogenic emissions of greenhouse gases in the face of scientific uncertainties about the details -- the magnitude, regional impacts, and rate of climate change. Climate-induced environmental changes cannot be reversed quickly, if at all, due to the long time scales associated with the climate system. Ultimately, it is not for scientists but rather for decisonmakers to decide what "dangerous" means under the Framework Convention on Climate Change.

Decisions taken during the next few years may limit the range of possible policy options in the future because high near-term emissions would require deeper reductions in the future to meet any given target concentration. Delaying action might reduce the overall costs of mitigation if potential technological advances are vigorously pursued in the interim, but could increase both the rate and the eventual magnitude of climate change, and hence the adaptation and damage costs.

Policymakers will have to decide on the degree to which they want to take precautionary measures by mitigating greenhouse gas emissions and enhancing the resilience of vulnerable systems by means of adaptation. Uncertainty does not mean that a nation or the world community cannot position itself better to cope with the broad range of possible climate changes or protect against potentially costly future outcomes. Delaying such measures may leave a nation or the world poorly prepared to deal with adverse changes and may increase the possibility of irreversible or very costly consequences. Options for adapting to change or mitigating change that can be justified for other reasons today (e.g., abatement of air and water pollution) and make society more flexible or resilient to anticipated adverse effects of climate change appear particularly desirable.

Finally, it is precisely the fact that aspects of global climate change remain uncertain that argues most strongly for a comprehensive research effort. Dealing with the issue of climate change requires a greater understanding of the Earth system. The complexity of the Earth system, a complexity agreed on by all those who have testified today, makes this an immense scientific challenge. I think nearly all the panelists would also agree that strong Federal science programs and Federally funded University research are critical to meet this challenge. The sheer magnitude of this task, combined with the seriousness of the potential consequences of climate change, provide a clear justification for the maintenance of a strong national research program focused on this issue.

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