Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 1
Summary of Recommendations There is no better example of the need for scientists and decision makers to work together than the broad range of issues concerning global environ- mental change, including greenhouse warming, stratospheric ozone deple- tion, tropical deforestation, and other changes not yet identified or pre- dicted. Policies to slow emissions or influence human behavior to mitigate or adapt to change must be based on scientific assessments of how the global environment will change in the future. The scientific information, however, is in many cases uncertain and incomplete, owing to our incom- plete understanding of the earth system and its interacting components. Substantial efforts on the part of the scientific community and federal sci- ence agencies will be required over the coming decades to improve our ability to understand the earth system and hence to project future changes in the global environment. With this perspective the U.S. Global Change Research Program (USGCRP) was initiated in FY 1990 as the federal government's effort to "establish the scientific basis for national and international policy-making relating to na- tional and human-induced changes in the global change earth system" (CES, 1990~. The objectives of the program are to establish an integrated, com- prehensive, long-term program of documenting the earth system on a global scale; develop integrated conceptual and predictive earth system models; and conduct a program of focused studies to improve understanding of the physical, geological, chemical, biological, and social processes that influ- ence earth system processes and trends on global and regional scales. The USGCRP embodies the U.S. scientific contributions to the two principal international research programs concerning global change, the International Geosphere-Biosphere Program (IGBP) of the International Council of Sci- entific Unions (ICSU), and the World Climate Research Program (WCRP) 1
OCR for page 2
2 RESEARCH STRATEGIES FOR THE USGCRP organized jointly under ICSU and the World Meteorological Organization. The former is addressing the interactive biological, physical, and chemical processes that regulate the earth system, and the latter is addressing the physically dynamic and radiative aspects of the climate system. This report recommends specific initiatives required to achieve the ob- jectives of the USGCRP to (1) document long-term changes in the earth system on a global scale and collect data necessary for process studies and modeling, (2) develop integrated models of the earth system, and (3) improve understanding of global change through focused studies of earth system processes. The initiatives discussed in this report elaborate on previous recommendations from the Committee on Global Change on initial priorities for U.S. contributions to the IGBP (NBC, 1988~. The recommendations are summarized below. INTEGRATED MODELING OF THE EARTH SYSTEM In order to develop a fully coupled, dynamical model of the earth system useful for projecting changes over a multidecadal time scale, a step-by-step buildup in complexity is required. The multidecadal time frame demands that changes in the biosphere and biogeochemical feedbacks, which happen over similar lengths of time, be incorporated into earth system models. For the near term, progress will be achieved through linking previously un- linked components of the earth system (e.g., coupling terrestrial systems with the atmosphere) or adding specific subsystems to existing models (e.g., coupling oceanic-atmospheric general circulation models (GCMs) or adding a marine biospheric model to an oceanic GCM). The committee recommends a focus on three critical subsystems, each of which represents an interface between various components of the earth sys- tem: · Models that couple the atmosphere-terrestrial subsystem. Modeling these interactions requires coupling successional models to biogeochemical mod- els to physiological models. The models must address how global environ- mental changes, including the effects of land use and chemical stress, affect terrestrial ecosystems and how ecosystem changes affect the global system. A primary challenge to be addressed is how processes with vastly differing rates of change, from photosynthesis to community change, are coupled to each other and to the atmosphere. Process studies and associated modeling activities are required to develop a better understanding of these processes, as discussed in chapters 5 and 6. · Models that couple the physics and the chemistry of the atmosphere. Progress in modeling these interactions requires a better understanding of the sources of trace gases, chemical processes and reaction channels in gas and aqueous phases, and transport processes by advection and convection. As with models
OCR for page 3
SUMMARY OF RECOMMENDATIONS 3 that couple the atmosphere-terrestrial subsystem, progress in modeling de- pends on improvements in understanding of fundamental physical and chemical processes and the nature of their coupling. · Models that couple the atmosphere and the ocean. Particularly impor- tant tasks are the scaling of the biological-biogeochemical components from local-regional domains to basin-global domains, formation of He upper mixed- layer physics, and possible biological feedbacks on mixed-layer dynamics such as shading due to phytoplankton blooms. The development of models should be encouraged along two parallel paths: one to develop basin- and global-scale models with increasing levels of coupling and a second to develop a series of regional fine-scale models that could provide boundary conditions and parameterization tests for the larger-scale models. As dis- cussed in chapter 7, existing and planned field programs offer valuable opportunities for improving fundamental understanding of oceanic processes and hence for improving modeling capabilities. Focusing on these three subsystems will not only provide the building blocks for fully integrated earth system models but also establish prototypes for the development of larger models. Even failure in these efforts can provide valuable lessons to the scientific community. Early tests of proto- typical earth system models, including tests using the record of the past (see chapter 3), should begin as soon as possible. FOCUSED STUDIES TO IMPROVE OUR UNDERSTANDING OF GLOBAL CHANGE The committee recommends that the following five initiatives be under- taken as focused studies to improve our understanding of global change. The initiatives are not intended to provide a comprehensive view of all the required studies within the USGCRP. Rather, they are contributions to the full suite of research needs covering a broad spectrum including the physi- cal climate, solid earth processes, and solar influences. Each of these initiatives requires a combination of process studies, mod- eling activities of the particular components of the system addressed by the initiative, and observations to collect pertinent data. The efforts to document and develop integrated models of the earth system support and are supported by these initiatives, but each initiative also has distinct data and modeling requirements. Earth System History and Modeling Earth history contains a rich record unique in its potential to provide comprehensive case studies in global change. The coupled response of climate, hydrology, biogeochemical cycles, and the biosphere to a large
OCR for page 4
4 RESEARCH STRATEGIES FOR THE USGCRP number of perturbations, including more recent human activities, is pre- served in these records. Understanding these linkages is essential for accurately predicting the future evolution of climate and the biosphere. Geologic observations also present the only opportunity to verify independently mod- els of how the earth system operates. The committee recommends that the following activities receive priority within the earth system history initiative: establishment of a global network of high-resolution climate histories for the Holocene (last 10,000 years) with emphasis on the last 1,000 to 2,000 years. These records will provide a frame of reference for compari- son with any future warming due to greenhouse gases. research to understand the origin of glacial-interglacial fluctuations. This research will provide an excellent opportunity to examine system re- sponse to known forcing. Special emphasis should be on (1) abrupt changes, (2) the carbon cycle, (3) tropical environments at the last glacial maximum, and (4) coupling of the different components of the climate system. evaluation of system response to large changes in boundary conditions. These studies will provide a sturdy test of climate models and enable evalua- tion of the linkages between climatic change and the biosphere. Research will focus on reconstruction of the environment of the Pliocene warm interval (3 to 5 million years ago) and evaluation of the climate-biosphere connection during the Eocene-Oligocene (30 to 40 million years ago) transition. Human Sources of Global Change In order to gain a systematic understanding of how human activities alter the global environment, particularly through changes in land use and indus- trial metabolism, the committee recommends that · integrative models of human sources of industrial emissions and land cover change be developed, particularly global models of how human ac- tivities relating to agriculture cause changes in chemical fluxes and land cover, global models of changes in greenhouse gas emissions from human sources, and regional models of how human activities cause land cover conversions of tropical forests and wetlands. · studies be initiated on the social and economic forces driving the following processes important for global change: fertilization in agriculture, biomass burning, and intensity of energy and material use. These studies will provide the understanding important for development of the integrative models noted above. data critical for model development and process studies be collected and organized with priority given to (1) a global data base allowing com- parisons of population and land cover, land use, and land capability data at
OCR for page 5
SUMMARY OF RECOMMENDATIONS a census district level and (2) a global data base on historical energy and materials use across a range of human activities. Water-Energy-Vegetation Interactions The goal of this research initiative is to develop the underlying under- standing and models of the interactions between the land biota and atmosphere, with particular reference to the exchanges of energy, water, heat, and trace gases. The process studies and models should explore the consequences of global change on terrestrial ecosystems and, ultimately, should be adequate to predict the response of the climate system to perturbations in ecosystems. The committee recommends that global monitoring be adequate to compile data sets for those param- eters necessary to calculate land surface-atmosphere fluxes of radiation, water, heat, and carbon dioxide. These parameters are vegetation index; cloudiness and precipitation; temperature, humidity, and wind speed; sur- face temperature; runoff; and soil type. process studies and field campaigns be initiated to test models relating biophysical and biochemical states to surface fluxes and remotely sensed variables, including models that link surface states and radiances, models that relate water use efficiency and concentrations of carbon and nutrients, and models that relate ecosystem structure and function and ecosystem re- sponse to global changes. · modeling initiatives be implemented including development of coupled land surface parameterizations (LSPs) and general circulation models (GCMs) for sensitivity studies of land use change and direct and indirect effects of increases in carbon dioxide; models describing fluxes; and ecophysiological models of carbon-water relations. Terrestrial Trace Gas and Nutrient Fluxes This initiative aims to (1) improve understanding of the ecosystem pro- cesses most important for determining the fluxes of radiatively active gases between the land and the atmosphere, in order to predict how changes in climate and land use alter gas emissions and (2) improve our understanding of the effects of land use changes on nutrient transfer to river, estuarine, and ocean systems, and especially of consequent feedbacks to climate through, for example, long-term changes in oceanic productivity. The committee recommends · measurements and models describing how changes in climate and eco- systems, precipitation, and land use alter carbon storage in ecosystems. · measurements and improved models for the major sources and sinks
OCR for page 6
6 RESEARCH STRATEGIES FOR THE USGCRP for carbon dioxide and the global pattern of carbon dioxide transport in the atmosphere. · process studies that relate methane production, consumption, and fluxes to environmental parameters and to changes in ecosystem structure and function. measurements of biogenic sulfur emissions (hydrogen sulfide. dimethylsulfide, carbonyldisulfide, and methyl mercaptan) from a variety of terrestrial ecosystems, especially those likely to be significant regional and global sources, e.g., wet tropical regions, coastal marshes, boreal forest peatlands, tundra bogs, rice paddies, landfills, and industry. · improvement of the data base describing ozone deposition in various ecosystems and the responses of ecosystems to acid deposition. . measurement and modeling of the fate of nutrients, pollutants, and sediments from terrestrial systems in streams and the oceans as affected by land use changes. · microscale and mesoscale models for extrapolating specific processes, such as trace gas source and sinks and fluxes, to regional and global scales. Biogeochemical Dynamics in the Ocean The objective of this initiative is to develop the capability to predict the effects of climatic change on the ocean's physical, chemical, and biogeo- chemical processes, especially as they feed back to climate via the release or absorption of radiatively important gases such as carbon dioxide and organic sulfur species. To meet this objective, the committee recommends the following: · U.S. support for the implementation phases of established projects relevant to understanding the role of the ocean in global change: the Joint Global Ocean Flux Study aGOFS), International Global Atmospheric Chemistry (IGAC), Tropical Ocean and Global Atmosphere (TOGA), and Global En- ergy and Water Cycle Experiment (GEWEX), including support for in situ and satellite observations, modeling, and linkages among these projects. · initiation of long-term systematic measurements of relevant oceanic properties and processes including dissolved carbon dioxide, ocean color, surface wind and currents, and rainfall with in situ and satellite techniques. initiation of coastal ocean studies to understand (1) the transfer of materials (nutrients and pollutants) from land to ocean and their sensitivity to global change (e.g., land use and changes in hydrological cycles and sea level) and (2) the dynamics of ecosystems, and how they can be influenced by global change, especially those ecosystem components particularly rel- evant to biogeochemical cycles and of particular commercial interest. .
OCR for page 7
SUMMARY OF RECOMMENDATIONS DOCUMENTING GLOBAL CHANGE The systems established to monitor global change over the coming de- cades, to provide data for process studies and modeling aimed toward im- proving our understanding of global change, and to manage the data and information so that they are accessible to researchers are crucial to the success of the USGCRP. Long-term global-scale monitoring needs are of two kinds: (1) to quan- tify the magnitude of the driving forces that may bring a long-term change in the state of the earth system, for example, solar irradiance, Face gas concentrations, and land use change, and (2) to monitor the state variables or "vital signs" of the earth where such changes are liable to manifest, for example, tropospheric, stratospheric, and surface temperature, ocean uptake of carbon dioxide, sea level, and soil and vegetation characteristics. Rela- tive priorities for monitoring individual variables must be judged not only in terms of their contribution to the monitoring requirements but also in terms of their importance for validating models and advancing our under- standing of specific processes and the readiness of the observation and analysis techniques involved. Globally synthesized products derived from measurements for example, a global data set for latent heat flux derived from data on radiation balance, temperature, moisture, and field studies-will be required to achieve the modeling objectives described in chapter 2. Data needs in relation to stud- ies of specific processes as discussed in chapters 3 through 7 of this report place additional requirements on the observation and monitoring program. In order to meet the data requirements for the USGCRP, satellite sys- tems, large-scale field studies, and surface networks are needed. The current international operational satellite system, satellite research missions, and a total system such as the Earth Observing System together provide the basis for the space-based portion of a global change observing system. Several surface observation networks such as the Background Air Pollution Monitoring Network (BAPMON) and networks organized by the World Meteorological Organization and the U.N. Environment Program contribute to the surface- based observational requirements. Existing ecological research sites such as the National Science Foundation's Long-Term Ecological Research Sites, as well as the planned IGBP Regional Research Centers, could also contribute. International coordination and data exchange, already fairly extensive for space-based programs, need to be strengthened for an effective overall glo- bal change observational strategy. An important concern with space-based observations is the discontinuity of key measurements such as global stratospheric ozone levels, the earth's radiation budget, and the biological productivity of oceans. In addition,
OCR for page 8
8 RESEARCH STRATEGIES FOR THE USGCRP research missions are needed to test technologies for direct satellite mea- surement of precipitation and soil moisture. The USGCRP will make unprecedented demands for the assembly and dissemination of large volumes of diverse data and information. Data and information must be accessible to researchers at the lowest cost possible, and the system must involve the scientific user community at all stages of development and operation. In addition, data documentation must be able to pass the "20-year test"; i.e., 20 years from now, someone unfamiliar with the data should be able to fully understand and use the data solely with the aid of the documentation archived with the data set. REFERENCES Committee on Earth Sciences (CES). 1990. Our Changing Planet: The FY 1991 U.S. Global Change Research Program. Federal Coordinating Council for Science, Engineering, and Technology. Office of Science and Technology Policy, Washington, D.C. National Research Council (NRC). 1988. Toward an Understanding of Global Change: Initial Priorities for U.S. Contributions to the International Geosphere- Biosphere Program. National Academy Press, Washington, D.C.
Representative terms from entire chapter: