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Multiple-stresses context. While Americans are concerned about climate change and its impacts, they do not think about these issues in isolation. Rather they consider climate change impacts in the context of many other stresses, including landuse change, consumption of resources, fire, and air and water pollution. This finding has profound implications for the design of research programs and information systems at the national

, regional, and local levels. A true partnership must be forged between the natural and social sciences to more adequately conduct assessments and seek solutions that address multiple stresses.

Urban areas. Urban areas provide a good example of the need to address climate change impacts in the context of other stresses. Although large urban areas were not formally addressed as a sector, they did emerge as an issue in most regions. This is clearly important because a large fraction of the U.S. population lives in urban areas, and an even larger fraction will live in them in the future. The compounding influence of future rises in temperature due to global warming, along with increases in temperature due to local urban heat island effects, makes cities more vulnerable_to higher temperatures than would be expected due to global warming alone. Existing stresses in urban areas include crime, traffic congestion, compromised air and water quality, and disruptions of personal and business life due to decaying infrastructure. Climate change is likely to amplify some of these stresses, although all the interactions are not well understood.

Impact, adaptation, and vulnerability. As the Assessment teams considered the negative impacts of climate change for regions, sectors, and other issues of concern, they also considered potential adaptation strategies. When considered together, negative impacts along with possible adaptations to these impacts define vulnerability. As a formula, this can be expressed as vulnerability equals negative impact minus adaptation. Thus, in cases where teams identified a negative impact of climate change, but could not identify adaptations that would reduce or neutralize the impact, vulnerability was considered to be high. A general sense emerged that American society would likely be able to adapt to most of the impacts of climate change on human systems but that the particular strategies and costs were not known.

Widespread water concerns. A prime example of the eed for and importance of adaptive responses is in the area of water resources. 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. Snowpack changes are especially important in the West, Pacific Northwest, and Alaska. Reasons for the concerns about water include increased threats to personal safety, further reduction in potable water supplies, more frequent disruptions to transportation, greater damage to infrastructure, further degradation of animal habitat, and increased competition for water currently allocated to agriculture.

Health, an area of uncertainty. Health outcomes in response to climate change are highly uncertain. Currently available information suggests that a range of health impacts is possible. At present, much of the U.S. population is protected against adverse health outcomes associated with weather and/or climate, although certain demographic and geographic populations are at greater risk. Adaptation, primarily through the maintenance and improvement of public health systems and their responsiveness to changing climate conditions and to identified vulnerable subpopulations should help to protect the U.S. population from adverse health outcomes of projected climate change. The costs, benefits, and availability of resources for such adaptation need to be considered, and further research into key knowledge gaps on the relationships between climate/weather and health is needed.

Vulnerable ecosystems. Many U.S. ecosystems, including wetlands, forests, grasslands, rivers, and lakes, face possibly disruptive climate changes. Of everything examined in this Assessment, ecosystems appear to be the most vulnerable to the projected rate and magnitude of climate change, in part because the available adaptation options are very limited. This is important because, in addition to their inherent value, they also supply Americans with vital goods and services, including food, wood, air and water purification, and protection of coastal lands. Ecosystems around the nation are likely to be affected, from the forests of the Northeast to the coral reefs of the islands in the Caribbean and the Pacific.

Agriculture and forestry likely to benefit in the near term. In agriculture and forestry, there are likely to be benefits due to climate change and rising CO2 levels at the national scale and in the short term under the scenarios analyzed here. At the regional scale and in the longer term, there is much more uncertainty. It must be emphasized that the projected increases in agricultural and forest productivity depend on the particular climate scenarios and assumed CO2 fertilization effects analyzed in this Assessment. If, for example, climate change resulted in hotter and drier conditions than projected by these scenarios, both agricultural and forest productivity could possibly decline.

Potential for surprises. Some of the greatest concerns emerge not from the most likely_future outcomes but rather from possible “surprises.” Due to the complexity of Earth systems, it is possible that climate change will evolve quite differently from what we expect. Abrupt or unexpected changes pose great challenges to our ability to adapt and can thus increase our vulnerability to significant impacts.

A vision for the future. Much more information is needed about all of these issues in order to determine appropriate national and local response strategies. The regional and national discussion on climate change that provided a foundation for this first Assessment should continue and be enhanced. This national discourse involved thousands of Americans: farmers, ranchers, engineers, scientists, business people, local government officials, and a wide variety of others. This unique level of stakeholder involvement has been essential to this process, and will be a vital aspect of its continuation. The value of such involvement includes helping scientists understand what information stakeholders want and need. In addition, the problemsolving abilities of stakeholders have been key to identifying potential adaptation strategies and will be important to analyzing such strategies in future phases of the assessment.

The next phase of the assessment should begin immediately and include additional issues of regional and national importance including urban areas, transportation, and energy. The process should be supported through a public-private partnership. Scenarios that explicitly include an international context should guide future assessments. An integrated approach that assesses climate impacts in the context of other stresses is also important. Finally, the next assessment should undertake a more complete analysis of adaptation. In the current Assessment, the adaptation analysis was done in a very preliminary way, and it did not consider feasibility, effectiveness, costs, and side effects. Future assessments should provide ongoing insights and information that can be of direct use to the American public in preparing for and adapting to climate change.

The CHAIRMAN. Thank you for being here.
Dr. Janetos.


Dr. JANETOS. Mr. Chairman, thank you for the opportunity to discuss the national assessment of potential impacts of climate change in the U.S.

There are really three questions about climate change that have dominated many of the public and scientific discussions: first, how much climate change is going to occur, second, what might happen as a result, and third, what can countries do about it?

The purpose of the national assessment is to focus only on the second of these questions. That is, to address the question of, so what, with our best understanding of the underlying science, and then to address the questions of major uncertainties in order to make well-reasoned recommendations for future research.

The national assessment was called for in the original enabling legislation in 1990 for the U.S. global change research program. In 1997, Dr. John Gibbons, then Science Advisor to the President, requested the global change research program to undertake the national assessment focusing on understanding other environmental stresses and issues within which climate change impacts might occur, whether climate change and variability might exacerbate or ameliorate existing problems, what options for coping might exist, and what research is most important to complete over both the short and the longer term.

A variety of efforts emerged in response to Dr. Gibbons' charge. First was a substantial bottom-up effort. Over 20 workshops were held around the country, involving a broad range of stakeholders, academics, farmers and ranchers, businesspeople, land managers, people from every walk of life.

Each workshop identified a range of issues of concern within their regions. Many of these were followed by the initiation of scientific studies, some of which have finished their work and have been published, others of which are ongoing.

At the same time, it was thought to be necessary to create a companion but independent effort to create a national level synthesis of what is known for the U.S. as a whole, addressing the issues that were raised in workshops, and addressing issues that have been raised in national studies of several important sectors.

This national study was viewed to build on work that has been done and published, on the published scientific literature, and on analyses that were to be done with the most up-to-date environmental data and models that could be obtained. All sources that were used in the national assessment and the national study were to be documented and to be available so that this study would present the best snapshot at this time of our understanding, using the best available information.

The national assessment synthesis team, which Mr. Karl, Dr. Melillo and I co-chair, was chartered under the Federal Advisory Committee Act specifically to carry out the national study. Its membership is drawn from academic and research institutions from industry, from nongovernmental organizations, and government research laboratories.

The first thing that we did was to publish a plan for the conduct of the national synthesis and select five issues for national analysis in addition to the work which Tom has just described on the different regions of the U.S. This plan was published in 1998 and has been available on the Internet.

The products of our work is now in two volumes. The first of these we call the foundation volume. It is over 600 pages long, with more than 200 figures and tables. It is extensively referenced and, as I mentioned, we have made the commitment that all of the sources, of which there are thousands used in it, are documented and are available. These are basically the same guidelines as the Intergovernmental Panel on Climate Change has used for the accessibility of source material.

The second volume we have called the overview. It is written more in a style for the general public. It is substantially shorter, about 150 pages long and extensively illustrated, and is a summary of the foundation document.

Both of these volumes have already undergone significant review. At the end of 1999 and the beginning of this year we went through two rounds of technical peer review. Subsequent to that, this past spring we went through an additional review by about 20 independent experts. We have received over 300 sets of comments and have made a commitment to document our responses to external comments that we have received.

In addition, we have written an overview memo summarizing our responses to major comments. We are now approximately half-way through a 60-day public comment period that was specifically requested by the Congress. When it ends, we anticipate responding to the additional comments we will have received, as we have done before, and putting the report in final form in order to be submitted to the President and Congress, as called for in the original legislation.

Throughout, the national assessment synthesis team has been the beneficiary of oversight review and guidance from an oversight panel which was established through the offices of the President's Council of Advisors on Science and Technology, chaired by Dr. Peter Raven and Dr. Mario Melina.

One thing I would like to emphasize in closing is that it is important to remember that the national assessment does not attempt to predict exactly what the future will hold for the U.S. It has examined the potential implications of two primary climate scenarios, but has used many other data sets as well. That is, it uses our best scientific understanding of ecosystems, hydrologic systems, agriculture, forestry, and so on, to explore the different consequences of scientifically plausible futures.

We explicitly discuss uncertainty in the underlying science. In fact, throughout the assessment we have consistently used language describing our scientific confidence in the results and findings so that the reader can understand when we are very confident of our findings and when we are less so.

Thank you very much.
The CHAIRMAN. Thank you very much. Dr. Schmitt.


Dr. SCHMITT. Thank you, Mr. Chairman. I am a physical oceanographer. In the past 25 years I have averaged about 1 month a year at sea on research cruises. In the past 10 years I have averaged about 1 month a year working on committees concerned with the role of the oceans in climate.

The thrust of my statement is that the oceans have a very important role to play in climate, and that we are not doing a very good job at either modeling the role of the oceans in climate predictions, nor are we properly monitoring the state of the ocean in order to make these predictions possible.

In the past few years oceanographers have done a large-scale survey of the state of the world ocean. We called it the World Ocean Circulation Experiment. It was funded by the National Science Foundation, and what we found was quite interesting.

In most areas—not all, but in most areas, deep waters had warmed significantly since the last time a major survey had been done in the fifties, so we are seeing global warming in the ocean. It is real, and we are finding it in the ocean and, in fact, the fact that we find it so deep in the ocean has been a surprise for many climate modelers, because the models they use have a very slow responding ocean. It is more like lava or concrete than the water that we know.

So oceanographers have a very different view of the ocean. We see a more active agent of climate change.

The CHAIRMAN. Why would it warm in-
Dr. SCHMITT. So deep?

Dr. SCHMITT. Well, it is quite interesting. The ocean interacts with the atmosphere at high latitudes, and the water can sink quite deeply. Up in the Labrador Sea, up in the seas off Greenland and Iceland, we call this deep convection, and this deep convection is how the ocean changes temperature, how it gives heat to the atmosphere and changes its own internal temperature, and this whole process—we call it the thermohaline circulation-is very important to transporting heat to high latitudes, for keeping Europe warm. The fact that England has a very moderate climate is due to this thermohaline circulation.

Well, one of the very exciting things that the paleoceanographers have found is that this circulation shut off at times in the past, when that water got too fresh. At the end of the last glaciation, about 12,000 years ago, there was a lot of fresh water coming from the melting glaciers. It shut off thermohaline circulation because adding fresh water makes the water lighter and it cannot sink, so then no heat was carried northward, Europe got very cold, and the ice ages came back for about 1,000 years.

The striking thing is that this change happened in a couple of decades, in the data that they have obtained from the ice core and in the sedimentary record at the bottom of the ocean. Some climate models predict an increase in high latitude rainfall due to the global warming. Warm air carries more water than cold air, and they have projected a shutdown in this thermohaline circulation. That would be a very significant change that could occur very rapidly.

Now, the other thing that we found in the last few years is that the ocean has certain temperature patterns that lock in specific climate phenomena. We all know about El Niño and la niña. That is warm water sloshing back and forth in the Pacific. Well, there is another oscillation called the North Atlantic oscillation, that seems to be controlled by the patterns of warm water moving around the North Atlantic.

We are at the stage technologically where we can make better measurements of these deep temperature patterns in the ocean with autonomous probes, floats that are like weather balloons for the ocean. They drift at depth, they inflate a small bladder ever 10 days, come to the surface and obtain a profile of temperature and salinity on the way up, send that data to a satellite, and then resubmerge for another 10-day drift.

From this we get the heat content of the ocean, we find out its salt content, and therefore whether it is likely to continue deep convecting in the winter. These things will help us to gain the ability to predict climate for 5 to 10 years in advance. We find this a very exciting research possibility.

The CHAIRMAN. What are you finding out?

Dr. SCHMITT. Well, the hope that we are holding out is that when we have enough data coming in from these new observation systems, and enough understanding of these processes, that we will be able to predict climate with greater confidence than we have now. Right now there is a great deal of uncertainty about all of these modes of operation.

The CHAIRMAN. When will you be able to start making these predictions?

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