US Senate Committee on Commerce, Science and Transportation Hearing on Climate Change Impacts on the United States: The Potential Consequences of Climate Variability and Change

Jerry M. Melillo, Co-chair
Ecosystems Center
Marine Biological Laboratory

Anthony C. Janetos, Co-chair,
World Resources Institute

Thomas R. Karl, Co-chair
NOAA National Climatic Data Center

We are very pleased to have the opportunity to address the Senate Committee on Commerce, Science and Transportation on the topic of the potential impacts of climate variability and change on the US. Our draft assessment report, Climate Change Impacts on the United States: the Potential Consequences of Climate Variability and Change was released for a 60 day public comment period on Monday, June 12. It is an extensive synthesis of the best available scientific information on this important topic.

There are three questions about climate change that dominate discussions of this important topic. How much climate change is going to occur? What will happen as a result? What can countries do about it? There are obviously heated political opinions about each of these, but the issues are real, and it is critical to understand the underlying scientific knowledge about each if sound decisions are to be made. The assessment report focuses on the second of these questions.

A national assessment of the potential impacts of climate change was called for in the 1990 legislation that established the US Global Change Research Program (USGCRP). For several years, the research program focused on developing the basic scientific knowledge that the international scientific assessment process overseen by the Intergovernmental Panel on Climate Change (IPCC ) depends on. The IPCC was jointly established by the World Meteorological Organization and the United Nations Environmental Programme in 1988. As scientific research has provided compelling evidence that climate change is in fact occurring, it has become increasingly clear that there is a need to understand what is at stake for natural resources and human well-being in the US. In response to this need, in 1998, Dr. John H. Gibbons, then Science Advisor to the President, requested the USGCRP to undertake a the national assessment originally called for in the legislation. Dr. Gibbons asked the USGCRP to investigate a series of important questions:

W h a t a r e t h e c u r r e n t e n v i r o n m e n t a l s t r e s s e s a n d i s s u e s f o r t h e U n i t e d S t a t e s t h a t f o r m a b a c k d r o p f o r a d d i t i o n a l i m p a c t s o f c l i m a t e c h a n g e ?

H o w m i g h t c l i m a t e c h a n g e a n d v a r i a b i l i t y e x a c e r b a t e o r a m e l i o r a t e e x i s t i n g p r o b l e m s ?

W h a t a r e t h e p r i o r i t y r esearch and information needs that can better prepare policy makers for making wise decisions related to climate change and variability? What information and answers to what key questions could help decision-makers make better-informed decisions about risk, priorities, and responses? What are the potential obstacles to information transfer?

W h a t r e s e a r c h i s m o s t i m p o r t a n t t o c o m p l e t e o v e r t h e s h o r t t e r m ? O v e r t h e l o n g t e r m ?

W h a t c o p i n g o p t i o n s e x i s t t h a t c a n b u i l d r e s i l i e n c e t o c u r r e n t e n v i r o n m e n t a l s t r e s s e s , a n d a l s o p o s s i b l y l e s s e n t h e i m p a c t s o f c l i m a t e c h a n g e ? H o w c a n w e s i m u l t a n e o u s l y b u i l d r e s i l i e n c e a n d f l e x i b i l i t y f o r t h e v a r i o u s s e c t o r s c o n s i d e r i n g b o t h t h e s h o r t a n d l o n g - t e r m i m p l i c a t i o n s ?

W h a t n a t u r a l r e s o u r c e p l a n n i n g a n d m a n a g e m e n t o p t i o n s m a k e m o s t s e n s e i n t h e f a c e o f f u t u r e u n c e r t a i n t y ?

W h a t c h o i c e s a r e a v a i l a b l e f o r improving our ability to adapt to climate change and variability and what are the consequences of those choices? How can we improve contingency planning? How can we improve criteria for land acquisition?

A variety of efforts emerged in response to Dr. Gibbons’ charge.

Over twenty workshops were held around the country, involving academics, business-people representing a range of industries including manufacturing, power generation and tourism, and people who work closely with land and water ecosystems including resource managers, ranchers, farmers, foresters and fishermen. Each workshop identified a range of issues of concern to stakeholders in those regions, many of them quite unrelated to climate change, per se. Most workshops were followed by the initiation of scientific, university-led regional studies, some of which have finished their work, and others of which are ongoing.

In addition to these kind of "bottom-up" efforts, it was decided that it was also necessary to create a national-level synthesis of what is known about the potential for climate impacts for the US as a whole, addressing the issues identified in the regional workshops and national studies. This synthesis obviously needed to build on the work that had begun to emerge from the subsequent regional and national studies, but also to draw on the existing scientific literature and analyses done with the most up-to-date ecological and hydrological models and data that could be obtained. The National Assessment Synthesis Team (NAST) was established by the National Science Foundation as an independent committee under the Federal Advisory Committee Act (FACA) specifically in order to carry out this second step. This committee is made up of experts from academia, industry, government laboratories, and non-governmental organizations (NGO’s) (membership list is Attachment 1). In order to ensure openness and independence, all meetings of the NAST have been open to the public, all documents discussed in its meetings are available through the National Science Foundation, as are all the review comments already received and responses to them. This is perhaps out of the ordinary for a scientific study; but most scientific studies do not focus on issues of such broad and deep implications for American society, and about which there is such heated rhetoric.

The NAST’s first action was to publish a plan for the conduct of the national synthesis. In addition, five issues (agriculture, water, forests, health, and coastal and marine systems), out of the many identified, were later selected by the National Synthesis Assessment Team (NAST) to be topics for national studies. Carrying out this plan has been a major undertaking. The end result has been the production of a comprehensive two-volume national assessment report, available to the public for a 60-day comment period. The "Foundation" volume is more than 600 pages long, with more than 200 figures and tables, with analyses of the five national sectors, and 9 regions that together cover the entire US. It is extensively referenced, and a commitment has been made that all sources used in its preparation are open and publicly available. The "Overview" volume is about 150 pages long, written in a style that is more accessible to the lay public, and summarizes the Foundation in a way that we hope will be understandable and informative, and which we are confident is scientifically sound. Both documents have already been through extensive review. At the end of 1999, two rounds of technical peer review were undertaken, and during the past spring, an additional review by about 20 experts outside the assessment process was undertaken. Over 300 sets of comments have been received from scientists in universities, industry, NGO’s, and government laboratories. The responses to all external comments have been described in comprehensive review memorandums. We are now in the final stage of the process, a 60 day public comment period specifically requested by Congress, after which final revisions will be done and the report submitted to the President and Congress, as called for in the original legislation.

In order to ensure that the NAST has undertaken its charge well, an oversight panel was also established through the offices of the President’s Council of Advisors on Science and Technology (membership list is Attachment 2). The oversight panel is chaired by Dr. Peter Raven, Director of the Missouri Botanical Garden and recently retired Home Secretary of the National Academy of Sciences, and Dr. Mario Molina, Professor of Atmospheric Chemistry at MIT, and recent Nobel-prize winner for his research on stratospheric ozone depletion. Its membership, like the NAST’s, is drawn from academia, industry, and NGO’s. It has reviewed and approved of the plans for the assessment, reviewed each draft of the report, and reviewed the response of the NAST to all comments.

What have been the results of this extraordinarily open process? What assumptions drive the analysis? What conclusions have been reached?

It is important to realize that the national assessment does not attempt to predict exactly what the future will hold for the US. It has examined the potential implications of two primary climate scenarios, each based on the same assumptions about future "business as usual" global emissions of greenhouse gases that the IPCC has used for many of its analyses. The two climate scenarios were based on output from two different global climate models used in the IPCC assessment. They are clearly within the range of global annual average temperature changes shown by many such models, one near the low and one near the high end of the range. Both exhibit warming trends for the US that are larger than the global average (Attachment 3). This is not surprising. For many years, one of the most robust results of global climate models has been that greater warming is expected in more northerly latitudes, and that land surfaces are expected to warm more than the global average. We have used assumptions that are entirely consistent with those used by the IPCC.

These climate scenarios describe significantly different futures that are all scientifically plausible, given our current understanding of how the climate system operates. As importantly, they describe separate baselines for analysis of how natural ecosystems, agriculture, water supplies, etc. might change as a result. In order to investigate such changes, i.e. the potential impacts of climate changes, the report relies on up-to-date models, on empirical observations from the literature, on investigations of how these systems have responded to climate variability that has been observed over the past century in the US, and on the accumulated scientific knowledge that is available about the sensitivities of resources to climate, and about how the regions of the US have and potentially could respond.

One additional important point about the scenarios should be mentioned. The report does not Amerge@ the results of models that disagree; it explicitly avoids doing so. The best example of this is in the analysis of potential changes in precipitation, where the two models used to create the scenarios give quite different results for some areas of the US. We have chosen to highlight these differences and explain that regional-scale precipitation projections are much more uncertain compared with temperature, rather than attempting to merge the results or guess which is more likely. The knowledge that the direction of precipitation change in some areas is quite uncertain is valuable for planning purposes, and clearly represents and important research challenge. There is however, consistency among models and observations on other aspects of precipitation changes. For example, both models and observations show an increase in the proportion of precipitation derived from heavy and extreme events as the climate warms (Attachment 4). So, both types of information are pertinent to help with the identification of potential coping actions. In this respect, the report follows the procedure that the IPCC itself uses for its global impacts reports, each of which examines the potential impacts for entire continents.

The US national assessment presents the results for each scenario clearly, and then takes the important additional step of explicitly describing the NAST’s scientific judgment about the uncertainty inherent in each result. Those results that are viewed to be robust are described in more terms; those viewed to be the result of poorly understood or unreconciled differences between models are described in more circumspect language. The lexicon of terms used to denote the NAST’s greater or lesser confidence is explicitly described in the beginning of the Overview report. This helps ensure that the report does not mask important results by thoughtlessly merging models, or overstating the scientific capability for assessing potential impacts. Finally, the report begins to identify possible options for adaptation to this changing world. It does not do a complete analysis of the costs, benefits, or feasibility of these options however, which is a necessary next step for developing policies to address these issues.

The report=s draft key findings (as more fully described in Attachment 5) present important observations for all Americans:

1. Increased warming. Assuming continued growth in world greenhouse gas emissions, the climate models used in this Assessment project that temperatures in the US will rise 5-101F (3-61C) on average in the next 100 years.

2. Differing regional impacts. Climate change will vary widely across the US. Temperature increases will vary somewhat from one region to the next. Heavy and extreme precipitation events are likely to become more frequent, yet some regions will get drier. The potential impacts of climate change will also vary widely across the nation.

3. Vulnerable ecosystems. Ecosystems are highly vulnerable to the projected rate and magnitude of climate change. A few, such as alpine meadows in the Rocky Mountains and some barrier islands, are likely to disappear entirely, while others, such as forests of the Southeast, are likely to experience major species shifts or break up. The goods and services lost through the disappearance or fragmentation of certain ecosystems are likely to be costly or impossible to replace.

4. Widespread water concerns. Water is an issue in every region, but the nature of the vulnerabilities varies, with different nuances in each. Drought is an important concern in every region. Floods and water quality are concerns in many regions. Snowpack changes are especially important in the West, Pacific Northwest, and Alaska.

5. Secure food supply. At the national level, the agriculture sector is likely to be able to adapt to climate change. Overall, US crop productivity is very likely to increase over the next few decades, but the gains will not be uniform across the nation. Falling prices and competitive pressures are very likely to stress some farmers.

6. Near-term increase in forest growth. Forest productivity is likely to increase over the next several decades in some areas as trees respond to higher carbon dioxide levels. Over the longer term, changes in larger-scale processes such as fire, insects, droughts, and disease will possibly decrease forest productivity. In addition, climate change will cause long-term shifts in forest species, such as sugar maples moving north out of the US.

7. Increased damage in coastal and permafrost areas. Climate change and the resulting rise in sea level are likely to exacerbate threats to buildings, roads, power lines, and other infrastructure in climatically sensitive places, such as low-lying coastlines and the permafrost regions of Alaska.

8. Other stresses magnified by climate change. Climate change will very likely magnify the cumulative impacts of other stresses, such as air and water pollution and habitat destruction due to human development patterns. For some systems, such as coral reefs, the combined effects of climate change and other stresses are very likely to exceed a critical threshold, bringing large, possibly irreversible impacts.

9. Surprises expected. It is very likely that some aspects and impacts of climate change will be totally unanticipated as complex systems respond to ongoing climate change in unforeseeable ways.

10. Uncertainties remain. Significant uncertainties remain in the science underlying climate-change impacts. Further research would improve understanding and predictive ability about societal and ecosystem impacts, and provide the public with useful information about adaptation strategies.

Given these findings it is clear that climate impacts will vary widely across the Nation, as one would expect for a country as large and ecologically diverse as the US. Natural ecosystems appear to be highly vulnerable to climate changes of the magnitude and rate which appear to be likely; some ecosystems surprisingly so. The potential impacts on water resources are an important issue in every region examined, although the nature of the concern is very different for the mountainous West than for the East. The potential for drought is a concern across the country. The nation’s food supply appears secure, but there are very likely to be regional gains and losses for farmers, leading to a more complex picture on a region-by-region basis. Forests are likely to grow more rapidly for a few decades because of increasing carbon dioxide concentrations in the atmosphere, but it is unclear whether those trends will be maintained as the climate system itself changes, leading to other disturbances such as fire and pest outbreaks. However, the climate change itself will, over time, lead to shifts in the tree species in each region of the country, some of them potentially quite profound. Coastal areas in many parts of the US and the permafrost regions of Alaska are already experiencing disruptions from sea-level rise and recent regional warming; these trends are likely to accelerate. Climate change will very likely magnify the cumulative impacts of other environmental stresses about which people are already concerned, such as air and water pollution, and habitat destruction due to development patterns. There are clearly links between human health, current climate, and air pollution. The future vulnerability of the US population to the health impacts of climate change depends on our capacity to adapt to potential adverse changes. Many of these adaptive responses are desirable from a public health perspective irrespective of climate change. Future assessments need to consider climate change in the context of the suite of environmental stresses that we all face. Perhaps most importantly, the report acknowledges very clearly that scientific uncertainties remain, and that we can expect surprises as this uncontrolled experiment with the Earth’s geochemistry plays out over the coming decades.

We hope that the public comment period will indeed result in a broad discussion of this draft report. This is, after all, a topic of immense importance and broad significance for Americans. We invite those with the interest to do so to participate by obtaining the current draft (www.usgcrp.gov), and to submit their comments, concerns, and criticisms. Our interest is in being as open and transparent as possible about what we have concluded, the scientific integrity of the results, and why we think they are important for us all.