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National Security Implications of Climate Change for U.S. Naval Forces 6 Future Research and Development Needs INTRODUCTION The domain of U.S. maritime forces—namely, coastal waters, the high seas, and shore-based facilities—is projected in Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) scenarios to be affected as climate is increasingly altered by rising atmospheric concentrations of greenhouse gases. Temperature data provide evidence for warming of the atmosphere and ocean over the past several decades. Estimates show that about 90 percent of the heat now accumulating in Earth’s climate system is being stored in the ocean.1 This fact is often underappreciated, however. Within the past few decades, direct measurements show that ocean temperatures across vast regions of the high seas are now elevated at depths of a thousand or more meters relative to the first half of the 20th century. Some of the incremental heat being retained by the enhanced greenhouse effect is affecting the ocean in another way: the melting of sea ice is changing maritime access in the Arctic and the melting of land ice is contributing to sea-level rise, as discussed in prior chapters. The mission of U.S. naval forces requires knowledge of ocean conditions. Historic databases, which constitute ocean climatology, are an essential component of forecasting and predicting systems used in several aspects of naval operations. It is clear that projected and reported climate change now under way is compromising the value of established climatologies that have been used for these purposes. 1 S. Levitus, J.I. Antonov, T.P. Boyer, R.A. Locarnini, H.E. Garcia, and A.V. Mishonov. 2009. “Global Ocean Heat Content 1955–2008 in Light of Recently Revealed Instrumentation Problems,” Geophysical Research Letters, Vol. 36, L07608.
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National Security Implications of Climate Change for U.S. Naval Forces This chapter provides an assessment of future climate change research and development (R&D) needs related to U.S. naval operations. Such needs are for supporting naval tactical operations and for providing improved data for future U.S. naval planning. The committee’s examination of topics for future R&D emphasis focuses on those areas in which the naval forces have particular interests that might not likely be met in the near term by other groups pursuing climate-related research. It is specifically recommended that the Navy address R&D issues related to climate observations, climate modeling, and sea-level rise, as well as needs unique to the Arctic. Other important climate research questions have implications for U.S. naval forces, but it is expected that many of these will be pursued in the course of ongoing and/or planned U.S. and international scientific programs. For example, there is a set of important questions related to the consequences of a decrease in ocean pH resulting from the increasing ocean absorption of carbon dioxide from the atmosphere. This is an area of basic research that the general scientific community is vigorously pursuing. Some aspects of ocean acidification that might be of special importance to the Navy—such as the potential effects of a pH decrease on sound absorption—are still under debate.2 The Navy should continue to monitor the research in ocean acidification closely, as the results may hold potential important implications for ocean acoustics critical to U.S. naval operations. The committee concluded that formulation of specific recommendations in this area would be premature. Improved understanding of how climate is changing will surely point to new research areas of particular importance for U.S. naval forces. As a nation, we need to be prepared for surprises. GLOBAL OBSERVATIONS, SCIENTIFIC ANALYSIS, AND MODELING IN SUPPORT OF NAVY R&D REQUIREMENTS Naval operations demand environmental information in the form of observations, model-based analysis products, and model forecasts for navigation, communication, general fleet support, antisubmarine warfare (ASW), and search and rescue. The Navy has long had programs in place to collect ocean and marine meteorological data for these purposes. It also has well-established weather, 2 Oceanographers Tatiana Ilyina and Richard Zeebe of the School of Ocean and Earth Science and Technology at the University of Hawaii at Manoa, together with Peter Brewer of the Monterey Bay Aquarium Research Institute, have hypothesized that seawater sound absorption will drop by up to 70 percent during this century. The scientists have examined the effects of human-made carbon dioxide under business-as-usual emissions and provide projections of the magnitude, timescale, and regional extent of changes in underwater acoustics resulting from ocean acidification. These changes are projected to be associated with the fact that low-frequency sound absorption depends on the concentration of dissolved chemicals such as boric acid, which in turn depends on seawater pH. These researchers also explained that further research is needed to address key questions in this area. See “Man Made Carbon Dioxide Affects Ocean Acoustics,” Science News, December 22, 2009.
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National Security Implications of Climate Change for U.S. Naval Forces ocean, and sea-ice modeling and forecasting capabilities. The Navy’s R&D efforts are intended to infuse new model, computing, and observational technologies into operational capabilities. At present, almost all data collection and modeling efforts within the Navy have a marine focus for tactical purposes. It is anticipated that requirements for such tactical scale observations will continue and that they will be an integral part of naval operations in the future. Here the committee addresses the related but distinct requirements for global-scale observations and modeling as part of a naval R&D climate change risk management strategy over the next 30 years. This R&D effort is intended to provide the information necessary for enhancing the U.S. Navy’s maritime domain awareness and for reducing uncertainties in seasonal to decadal timescale forecasts that guide long-range Navy planning. Projected effects of climate change suggest it will alter the physical environment in which the Navy operates in the coming decades. Warming ocean and land temperatures, rising sea levels, disappearing Arctic sea ice, shrinking glaciers and ice sheets, shifts in rainfall patterns, and changes in storm frequency, intensity, and spatial distribution are among the projected manifestations of climate change. The implications of these changes are such that the climatological databases that the U.S. naval forces have used in the past may no longer be valid in the future. Against this backdrop, U.S. naval forces will become even more dependent in the future on observations, analysis products, and forecasts of the global environment to carry out its mission. The U.S. naval forces’ needs will be largely focused on the maritime environment as in the past; because of their humanitarian assistance/disaster relief (HA/DR) mission and shore-based facilities, however, naval forces will also require information on evolving environmental conditions in continental regions where vulnerabilities to climate change are greatest. There will also be regions, like the Arctic, that require special attention because of the unique mix of environmental, societal, and national security issues that they present. Current Status of Global Ocean Observations To carry out its mission, the U.S. Navy needs many ocean, atmosphere, cryosphere, and land measurements. Key parameters that need to be measured in the marine environment to support naval operations include temperature, salinity, ocean currents, surface waves, coastal sea level, sound speed, ambient noise, and, in polar regions, sea-ice extent and thickness. Marine meteorological measurements are also needed for winds, air temperature, pressure, relative humidity, precipitation, and other parameters. At present, these data are required to support fleet operations on tactical timescales and space scales. They are used primarily for describing current conditions and for forecasting evolving conditions in the oceans and the atmosphere on timescales of about a few days to a week. The discussions in this section extend beyond the tactical scale to address global
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National Security Implications of Climate Change for U.S. Naval Forces sustained ocean observing systems for climate and how they can address future mission goals of the Navy. Currently, global measurements in the marine environment come from a mix of Earth observing satellites and in situ sensors as part of the Global Ocean Observing System (GOOS) and the Global Climate Observing System (GCOS). GOOS and GCOS represent international coordination efforts sponsored by the International Oceanographic Commission (IOC), World Meteorological Organization (WMO), and International Council for Science (ICSU) dating back to the early 1990s. The United States is the single largest contributor to these programs, with most U.S.-sponsored measurements made by civilian agencies such as NASA-, National Oceanic and Atmospheric Administration (NOAA)-, and National Science Foundation (NSF)-sponsored researchers. There is a premium placed on real-time and near-real-time data availability as it enables timely and routine monitoring while providing data for weather and climate forecast model initialization. Elements of this observing system include NOAA and NASA satellites that are a critical source of information on the global- and regional-scale ocean sea-surface-temperature warming trends. Sea-level rise over the past 15 years has been tracked by NASA and European Space Agency (ESA) altimeter missions. In situ components include moored and drifting buoy arrays, such as the Argo float program.3 These and other satellite and in situ measurement efforts benefit Navy operational weather and ocean forecasting at the Navy’s Fleet Numerical Meteorology and Oceanography Center (FNMOC), and the Commander, Naval Meteorology and Oceanography Command (CNMOC), by providing key data sets for model initialization and verification. A recent technical conference highlighted the history, status, and plans for further development of the ocean observing system, with nearly 100 community white papers published on the subject as part of its proceedings.4 The Navy and the Department of Defense (DOD) have measurement assets geared toward addressing the needs of their specific mission sets, but which contribute to the ocean observing system. These include, for example, the polar-orbiting satellites of the Defense Meteorological Satellite Program (DMSP), from which much of the data is declassified and publicly available. DMSP data, together with data from NOAA and NASA satellites, have provided the clearest evidence for diminished Arctic sea ice in summer. 3 Argo is a global array of 3,000 free-drifting profiling floats that measures the temperature and salinity of the upper 2,000 m of the ocean, allowing continuous monitoring of the temperature, salinity, and velocity of the upper ocean. All Argo data are relayed and made publicly available within hours after collection. 4 For a summary of OceanObs09, see D.E. Harrison and David M. Legler, 2009, “Saltier, Hotter, More Acidic, and Less Diverse? Observing the Future Ocean,” EOS, Transactions American Geophysical Union, Vol. 91, No. 3, p. 23. See also a compilation of meeting papers at http://www.oceanobs09.net/. Accessed June 4, 2010.
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National Security Implications of Climate Change for U.S. Naval Forces There are classified Navy and DOD measurements and assets whose access is restricted for reasons of national security. These could make significant contributions to GOOS if more open access were provided. Classified historical data would be invaluable in developing observational baselines for gauging current and future climate change. The committee believes that additional such data can be released that would not be harmful to national security, nor would it compromise other sensitive information concerning the types of measurements, methods, equipment, positional requirements, and so on. As one example, release of images of Arctic sea ice from 1999 to the present as part of the Measurements of Earth Data for Environmental Analysis (MEDEA) Program is providing unique and fundamentally new information on the loss of Arctic sea ice, which is largely attributable to climate change.5 In another example, the release of Arctic sea-ice draft data derived from submarine upward looking sonar from the Navy’s Arctic Submarine Laboratory provides a critical long-term estimate of sea-ice thickness since 1975.6 Despite the widespread interest nationally and internationally in developing a global ocean observing system for climate, there are significant challenges that limit progress in addressing some of the most pressing problems. For example, it is not possible yet to routinely measure properties in the deep ocean below 2,000 meters from autonomous platforms. These measurements are needed to accurately document the ocean’s storage of heat. Similarly, western boundary currents like the Gulf Stream are critical conduits for meridional transport of oceanic mass, heat, and salt to the poles. Current data collection technologies make it difficult and expensive to consistently gather long-term measurements in these high-velocities regions. The Arctic, discussed in more detail later, is a particularly challenging environment for sustained ocean observing systems because of its extreme cold, remoteness, and ice cover most of the year, even though half of the Arctic basin lies within the exclusive economic zones (EEZs) of rim nations. From a climate perspective, data records have greatest value when they are multiyear to multi-decadal and longer in length, continuous in time, and with sufficient meta-data to properly interpret. These attributes imply that developing a sustained ocean observing system for climate will require partnerships between agencies and nations that share common interests. The investment requirements for continuity and long-duration measurements, coupled with regional- to global-scale spatial coverage, suggest that pooling and coordination of resources are the best strategy for sustaining ocean observations. The Navy historically supported large-scale ocean measurement programs 5 National Research Council. 2009. Scientific Value of Arctic Sea Ice Imagery Derived Products, The National Academies Press, Washington, D.C. 6 See D.A. Rothrock, Y. Yu, and G.A. Maykut, 1999, “Thinning of the Arctic Sea-Ice Cover,” Geophysical Research Letters, Vol. 26, No. 23, pp. 3469-3972; and D.A. Rothrock, D.B. Percival, and M. Wennahan, 2008, “The Decline in Arctic Sea-Ice Thickness: Separating the Spatial, Annual and Interannual Variability in a Quarter Century of Submarine Data,” Journal of Geophysical Research, Vol. 113, C05003.
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National Security Implications of Climate Change for U.S. Naval Forces through Office of Naval Research (ONR) funding. For example, in the 1970s and 1980s, as part of the North Pacific Experiment (NORPAX), the Navy and NOAA jointly supported ship-of-opportunity and other measurements to document large-scale temperature anomalies in the North Pacific that were believed to affect North American weather and climate. However, over the past two decades, the Navy has greatly reduced its support of such large-scale ocean measurement efforts related to climate. FINDING 6.1: The interconnectedness of the global ocean circulation, the involvement of processes spanning the full water column, the requirement to measure coast-to-coast across ocean basins, and the need for continuous long-term records represent daunting challenges to advancing understanding of climate variability and change. In view of these challenges, U.S. civilian agencies, in collaboration with international partners, have established a framework dating back to the early 1990s to advance the development of the Global Ocean Observing System (GOOS). Over the same time period, the U.S. Navy has withdrawn its support for large-scale ocean measurement programs; at present, it has little involvement in Global Ocean Observing System development. The Navy relies almost entirely on civilian agencies and their international partners for global-scale climate-related ocean measurement programs, which may fail to address specific Navy concerns. RECOMMENDATION 6.1: The Office of Naval Research should reevaluate its long-standing decision to not support large-scale ocean measurement programs and instead participate directly in the large-scale sustained measurement programs that would support development of the Global Ocean Observing System. FINDING 6.2: Open access to previously classified Navy data and to other Department of Defense assets through the MEDEA Program has enabled advances in climate change research that have benefited the scientific community studying climate change. A clear example of this benefit is the analysis of submarine upward looking sonar, which shows that sea ice has been thinning in response to climate change. RECOMMENDATION 6.2: The Chief of Naval Research, the Oceanographer of the Navy, and the Commander, Naval Meteorology and Oceanography Command, should consider findings by the MEDEA Program (and take lessons from MEDEA actions within the intelligence community) to develop and support a Navy philosophy for providing access to previously classified information that can be used by the climate research community. Such actions would enhance the potential of these researchers to help the Navy better prepare for its mission in a future with a warmer climate.
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National Security Implications of Climate Change for U.S. Naval Forces Current Status of Climate Change Modeling Climate modeling has rapidly evolved in recent years as a result of higher spatial resolution; better representation of physical processes; coupling of atmosphere, ocean, and land components; and the availability of a diverse array of observations. As the U.S. Navy considers the potential impact of climate change on its operations and national security, it is clear that evolutionary and transformational advances may be required to improve modeling and prediction of seasonal, decadal, and longer-term (century scale) climate. In particular, projections must provide sound estimates of the probability of the opening of the Arctic seas and high-risk events such as hurricanes, drought, and flooding. Sea-level rise and its consequences are also a primary model estimate of importance for operational planning beyond the next few decades. Climate model projections based on external forcing of the climate system and predictions that, in addition, take into account initial conditions will be of great value for planning national security strategies in response to climate change and its impacts in the next few decades. Decadal prediction will be a new focus of the next Intergovernmental Panel on Climate Change (IPCC).7,8 One of the challenges is determining how to properly initialize ocean and sea-ice models with observed climate conditions. The approach is a natural merger of ongoing efforts in seasonal-interannual and decadal forecasting.9 NOAA’s Climate Prediction Center (CPC) is a leading agency in the development of a robust Climate Forecast System and National Multi-Model Ensemble (NMME) system.10 Involvement in these new efforts by the Navy at this planning stage could ensure that they are designed to meet the needs of the naval forces. It is still quite challenging to assess climate model value or success because simulations from even the most advanced modeling systems have considerable spread and uncertainty. Carefully quantifying this uncertainty, especially at the regional scale, is necessary to evaluate the potential impacts of climate change. One effort is to create large ensembles of model simulations by varying uncertain 7 Gerald A. Meehl, Lisa Goddard, James Murphy, Ronald J. Stouffer, George Boer, Gokhan Danabasoglu, Keith Dixon, Marco A. Giorgetta, Arthur M. Greene, Ed Hawkins, Gabriele Hegerl, David Karoly, Noel Keenlyside, Masahide Kimoto, Ben Kirtman, Antonio Navarra, Roger Pulwarty, Doug Smith, Detlef Stammer, and Timothy Stockdale. 2009. “Decadal Prediction: Can It Be Skillful?” Bulletin of the American Meteorological Society, pp. 1465-1485. 8 James Hurrell, Gerald A. Meehl, David Bader, Thomas L. Delworth, Ben Kurtman, and Bruce Wielecki. 2009. “A Unified Approach to Climate System Prediction,” Bulletin of the American Meteorological Society, pp. 1819-1832. 9 Alberto Troccoli and T.N. Palmer. 2007. “Ensemble Decadal Predictions from Analyzed Initial Conditions,” Philosophical Transactions of the Royal Society A, 365, No. 1857. 10 University Corporation for Atmospheric Research. 2009. Community Review of the NCEP Climate Prediction Center, December. Available at http://www.ncep.noaa.gov/director/ucar_reports/CPC_Report_UCAR_Final.pdf. Accessed August 2, 2010.
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National Security Implications of Climate Change for U.S. Naval Forces physical parameters.11 Progress is being made to improve climate models, but current modeling efforts suffer from insufficient resolution of features at various scales, including fronts, tropical-mid-latitude interactions, atmosphere-ocean exchanges, winds, precipitation, and salinity. Ocean components of climate models are relatively laminar (not turbulent) and do not capture energetic eddy flows at the sub-10 km scale.12 New advances are also needed with respect to glacial ice. Current glacial models coupled to atmosphere or ocean models only account for superficial melting and accumulation rather than potential dynamic discharge by glacial flow, which may be critical for understanding future sea level. The next generation of climate models must properly resolve carbon and other biogeochemical cycles to reach the goals of an Earth system modeling framework.13 Uncertainties about carbon-feedback processes in the ocean and on land must be resolved to improve future predictions of climate change. The next IPCC assessment will include coupled modeling systems with interactive carbon cycles.14 Refinements in ocean biochemistry modules in climate models are also required. Expanding climate models to include these new processes with credible methods has resulted in a massive increase in the computing requirements, even at the standard resolutions of the IPCC Fourth Assessment Report (AR4). Increasing resolution will improve parameterization of clouds, ocean mixing, and ice sheets, but current high-performance computing resources are insufficient to resolve major issues associated with these processes. Also, the role of aerosols 11 J.M. Murphy, D.M. Sexton, D.N. Barnett, G.S. Jones, M.J. Webb, M. Collins, and D.A. Stainforth. 2004. “Quantification of Modeling Uncertainties in a Large Ensemble of Climate Change Simulations,” Nature, Vol. 430, pp. 768-772. 12 David C. Bader, Curt Covey, William J. Gutowski, Isaac M. Held, Kenneth E. Kunkel, Ronald L. Miller, Robin T. Tokmakian, and Minghua H. Zhang. 2008. “Climate Models: An Assessment of Strengths and Limitations,” synthesis and assessment product 3.1, U.S. Climate Change Science Program and the Subcommittee on Global Change Research Report. Available at http://www.climatescience.gov/Library/sap/sap3-1/final-report/default.htm. Accessed June 4, 2010. 13 See National Research Council, 2007, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, The National Academies Press, Washington, D.C.; and National Research Council, 2008, Earth Observations from Space: The First 50 Years of Scientific Achievements, The National Academies Press, Washington, D.C. 14 M.A. Shapiro, Jagadish Shukla, Gilbert Brunet, Carlos Nobre, Michael Béland, Randall Dole, Kevin Trenberth, Richard Anthes, Ghassem Asrar, Leonard Barrie, Philippe Bougeault, Guy Brasseur, David Burridge, Antonio Busalacchi, Jim Caughey, Deliang Chen, John Church, Takeshi Enomoto, Brian Hoskiins, Øystein Hov, Arlene Laing, Hervé Le Treut, Jochem Marotzke, Gordon McBean, Gerald Meehl, Martin Miller, Brian Mills, John Mitchell, Mitchell Moncrieff, Tetsuo Nakazawa, Haraldur Olafsson, Tim Palmer, David Parsons, David Rogers, Adrian Simmons, Alberto Troccoli, Zoltan Toth, Louis Uccellini, Christopher Velden, and John M. Wallace. 2010. “An Earth-System Prediction Initiative for the 21st Century: An International Interdisciplinary Initiative to Accelerate Advances in Knowledge, Prediction, Use and Value of Weather, Climate and Earth-System Information,” National Center for Atmospheric Research, Boulder, Colo. Available at http://www.cgd.ucar.edu/.../ShapiroetalVisionDocument_FINALJan13_2010.pdf. Accessed June 4, 2010.
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National Security Implications of Climate Change for U.S. Naval Forces (liquid and solid particles in the atmosphere) is a major source of uncertainty in quantitative attribution and observational studies. Aerosols affect both radiation balance and cloud microphysical processes, yet they are very poorly represented in climate models. For a meaningful translation of climate model information to regional and societal applications, current output is still on relatively coarse spatial scales. The well-known inconsistency between models’ spatial resolution and scale of impact/decision making is challenging. And while computing resources will continue to improve spatial resolution and representation of physical processes, downscaling techniques (both dynamical and statistical) will likely be needed to overcome scale mismatches. Further, climate models should be more strongly coupled with decision support tools, models, and information systems that nonscientists and stakeholders use for decision making. The U.S. Navy is a good example of a stakeholder that has very specific needs in applications related to its infrastructure and operations, disease, civil instability, migration, water resources, and energy. A “holistic” modeling approach spans the climate, weather, and human dimension scale; it requires a seamless integration of chemistry, physics, climatology, meteorology, mathematics, and social and decision sciences.15 An example of progress in this area is the University Corporation for Atmospheric Research (UCAR) Africa initiative on tropical health-climate-weather linkages.16 The U.S. Navy is not involved in coupled climate modeling or climate forecasting on any timescale. Most Navy modeling focuses on short tactical timescales and space scales for day-to-day fleet operations.17 The Naval Research Laboratory (NRL) at Stennis Space Center, Mississippi, runs ocean models forced with prescribed atmospheric boundary conditions so that there are no feedbacks between the ocean and the atmosphere as in a truly coupled system, other than for 5-day sea-ice forecasting in the Arctic, done with the dated polar ice projection system. Model forecast systems under development at NRL are for the ocean only and are intended to infuse new technology into the Navy operational ocean forecasting at CNMOC; generally these model forecasts extend to 7 days in the future. Weather forecasting is carried out at FNMOC in support of fleet operations, but does not extend past 5-day lead times. In short, there is no capability for coupled ocean-atmosphere-land-cryosphere modeling in the Navy, and there are no programs focused on seasonal-to-decadal timescale predictions to support strategic decisions related to operations, platforms, and facilities. Because of the U.S. Navy’s presence on the global oceans, its long-term global ocean/ice observations and 15 Ibid. 16 Information on the UCAR Africa initiative is available at http://www.africa.ucar.edu/index.html. Accessed June 4, 2010. 17 These models include the Naval Research Laboratory’s real-time Global Ocean Analysis and Modeling and 120-hour forecasts of ocean and sea ice made with the Polar Ice Prediction System and the Cox ocean model or the operational Arctic sea-ice charting done in collaboration between the National Ice Center and NOAA.
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National Security Implications of Climate Change for U.S. Naval Forces data collection, and its unique physical assets, the Navy can both benefit from and contribute strongly to a better understanding of the ocean component of climate science.18 Sea-Level Rise Modeling Needs In the ranking of the top 20 cities in terms of population with projected exposure to coastal flooding in the 2070s, Miami ranks 6th and New York City 17th; the other 18 cities are all located in southeast Asia.19 The total estimated 2070 population exposed to coastal flooding in the 10 most vulnerable cities tops 80,000,000 people. When smaller exposed coastal cities for these same nations are tallied, the total exposed population that could be in need of HA/DR assistance due to coastal storm damage is higher by two- to threefold (see Figure 6.1). The need for better models and understanding of coastal vulnerabilities thus has broader implications for naval forces than simply understanding the risks associated with naval coastal infrastructure. One particularly good example of the potential of a vulnerability analysis to guide decisions relating to coastal exposure to storm surge in a future warmer world is that undertaken by Kelinosky et al.20 The focus of their study was Hampton Roads, Virginia, at the nexus of the York and James Rivers, the Chesapeake Bay, and the Atlantic Ocean. Researchers in the Hampton Roads study mapped physical exposure to storm-surge flooding for all categories of hurricane, for both present and future sea levels, using what would today be judged as conservative estimates for the latter. A total of 57 variables derived from the 2000 United States Census were used in a principal components analysis of social vulnerability. Maps of socioeconomic characteristics commonly associated with vulnerability to environmental 18 For example, tracer-transport inversion is one of several methods for estimating greenhouse gas emissions, and it is based on atmospheric and/or oceanic measurements of the gases and mathematical models of air and water flow. Tracer-transport inversion estimates the net sum of anthropogenic and natural sources and sinks. The use of this method has been hypothesized as being potentially useful in estimating greenhouse gas emissions to support anticipated future climate treaty obligations. If such a scenario were to develop, this committee speculates that the U.S. Navy’s instrument deployment and ocean data collection capabilities might also play a potential supporting role. See National Research Council, 2010, Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements, The National Academies Press, Washington, D.C. 19 R.J. Nicholls, P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. Ragoonaden, and C.D. Woodroffe. 2007. “Coastal Systems and Low-Lying Areas,” Climate Change 2007: Impacts, Adaptation and Vulnerability, contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson (eds.), Cambridge University Press, Cambridge, United Kingdom, pp. 315-356. 20 Lisa R. Kelinosky, Brent Yarnal, and Ann Fisher. 2007. “Vulnerability of Hampton Roads, Virginia, to Storm-Surge Flooding and Sea-Level Rise,” Natural Hazards, Vol. 40, No. 1, pp. 43-70.
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National Security Implications of Climate Change for U.S. Naval Forces FIGURE 6.1 Top 15 countries by population exposed today and in the 2070s to coastal flooding, showing the influence of future climate change and socioeconomic change. SOURCE: R.J. Nicholls, S. Hanson, C. Herweijer, N. Patmore, S. Hallegatte, Jan Corfee-Morlot, Jean Chateau, and R. Muir-Wood. 2007. Ranking of the World’s Cities Most Exposed to Coastal Flooding Today and in the Future, Organisation for Economic Cooperation and Development (OECD), Paris. Courtesy of OECD, 2007, “Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposures Estimates,” Environment Working Paper No. 1, available at http://www.oecd.org/env/workingpapers. hazards are compared to the flood-risk exposure zones to identify the locations of vulnerable subpopulations. Scenarios that address uncertainties regarding future population growth and distribution are also developed to provide guidance that could help to diminish the vulnerability of future inhabitants of any metropolitan region to storm-surge flooding. A summary statement in the U.S. Climate Change Research Program (2009) report on sea-level rise clearly describes the urgent need for new work on this topic: “The prospect of accelerated sea-level rise and increased vulnerability in coastal regions underscores the immediate need for improving our scientific understanding of and ability to predict the effects of sea-level rise on natural systems and society. These actions, combined with development of decision support tools for taking adaptive actions and an effective public education program, can lessen the economic and environmental impacts of sea-level rise.”21 21 James G. Titus, Eric K. Anderson, Donald R. Cahoon, Stephen Gill, Robert E. Thieler, and Jeffress S. Williams. 2009. Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region, U.S.
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National Security Implications of Climate Change for U.S. Naval Forces THE SPECIAL CASE FOR UNDERSTANDING CHANGES IN THE ARCTIC The retreat of Arctic sea ice in summer is fundamentally altering the naval forces’ mission by allowing increasing access to the harsh and highly variable Arctic environment. As stated earlier in this report, the Arctic Ocean is in many ways the most poorly observed of the world’s oceans: there are deficiencies in bathymetric charts, sparse knowledge of sea-ice thickness, infrequent measurements of ocean salinity and temperature, and so on. Current efforts to establish the first comprehensive, sustained in situ observing system in the Arctic are reviewed in this section, as is the state of climate modeling and seasonal forecasts of sea ice and Arctic climate that could prove valuable for planning Arctic operations. The decline of the yearly minimum sea-ice cover in September is more than 10 percent per decade during the satellite era (since 1979; see Figure 2.3 in the operations section), and the decline appears to be accelerating. According to submarine sonar estimates of draft, the thickness of ice decreased by more than a meter from 1980 to 2000.22 The Canadian archipelago has never allowed ice-free passage in the historical record until two summers in this decade—a prediction that was made at the 2001 symposium on “Naval Operations in an Ice-Free Arctic.”23 Observations and models indicate the Arctic ice cover is losing its multiyear ice and transitioning to a situation more like the Antarctic, which is mostly first-year ice covered with very little sea ice at the end of the melt season.24,25 Natural variability in the sea-ice extent is large in summer, so a given year can be far above or below (by at least 15 percent) the long-term trend. Explanations after the fact for the record minimum in 2007 are many-faceted,26 which is evidence that a complete understanding of the mechanisms of sea-ice variability remains elusive. Predicting such fluctuations would be valuable, and a nascent effort known as the Sea Ice Outlook Project summarizes the community effort to produce Arctic-wide and regional forecasts 2 to 4 months in advance (http://www.arcus.org/search/seaiceoutlook/). Climate Change Science Program and the Subcommittee on Global Change Research, U.S. Environmental Protection Agency, Washington, D.C., p. ix. 22 D.A. Rothrock, D.B. Percival, and M. Wensnahan. 2008. “The Decline in Arctic Sea-Ice Thickness: Separating the Spatial, Annual and Interannual Variability in a Quarter Century of Submarine Data,” Journal of Geophysical Research, Vol. 113, C05003. 23 See Office of Naval Research, 2001, Naval Operations in an Ice-Free Arctic Symposium: Final Report, Arlington, Va., April. 24 Josefino C. Comiso. 2002. “Warming Trends in the Arctic from Clear Sky Satellite Observations,” Journal of Climate, Vol. 16, pp. 3498-3510. 25 J.A. Maslanik, C. Fowler, J. Stroeve, S. Drobot, J. Zwally, D. Yi, W. Emery. 2007. “A Younger, Thinner Arctic Ice Cover: Increased Potential for Rapid, Extensive Sea-Ice Loss,” Geophysical Research Letters, Vol. 34, L24501. 26 Eric T. DeWeaver. 2008. “Arctic Sea Ice Decline: Introduction,” Arctic Sea Ice Decline: Observations, Projections, Mechanisms and Implications, E.T. DeWeaver, C.M. Bitz, and B. Tremblay (eds.), pp. 1-6.
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National Security Implications of Climate Change for U.S. Naval Forces FIGURE 6.2 Percent loss at 2030 relative to 2005 (from 10-year means centered on these years) in models used for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) from the Special Report on Emissions Scenarios (SRES) A1B (a balanced emphasis on all energy sources) scenario. Data were downloaded from the Coupled Model Intercomparison Project Phase 3 website. The models highlighted in pale blue are the only two models that agree with the observed mean and trend during the satellite era. SOURCE: Data adapted from the Coupled Model Intercomparison Project Phase 3 website at http://www-pcmdi.llnl.gov/ipcc/about_ipcc.php. Accessed April 8, 2011. The effort began in 2008, motivated in part by the failure to anticipate the record low in 2007. Climate models uniformly project continued sea-ice reduction in the 21st century, with most having a greater rate of thinning than reduction in extent.27 However, many models correlate poorly with the observed sea-ice cover in the 20th century.28 The spread in future projections is very broad—as is illustrated in Figure 6.2 with a histogram of the percent loss of Arctic September sea ice in 27 Kyle Armour, Cecilia M. Bitz, LuAnn Thompson, Elizabeth H. Hunke, submitted, “Controls on Arctic Sea Ice First-Year and Multi-Year Ice Survivability.” American Geophysical Union, Fall Meeting, 2009. 28 Juliette Stroeve, Marika M. Holland, Walt Meier, Ted Scambos, and Mark Serreze. 2007. “Arctic Sea Ice Decline: Faster Than Forecast,” Geophysical Research Letters, Vol. 34, L09501.
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National Security Implications of Climate Change for U.S. Naval Forces 2030 relative to 2005. Figure 6.2 illustrates two key issues for Arctic operations. First, the sea-ice projections from climate models today are so broad that clearly a risk management approach is needed. Second, about one-quarter of the models project faster decline in the next 20 years than has been observed during the satellite era. The two models that agree with observations during the satellite era have above-average decline among models in the future. These same two models have ice-free conditions (i.e., the area falls below 1 million square kilometers) in September by roughly the years 2040 to 2060. The spotlight on sea-ice projections from the last IPCC report (AR4) is likely to cause a step-change improvement in sea-ice modeling. The most profitable avenue of improvement is likely to be realized from improving the sea-ice climatology through tuning the model, as the climatology has been shown to have a substantial bearing on the subsequent trend.29,30 There is likely to be substantial value from improving processes in the sea-ice component as well.31 Stimulated by the magnitude of Arctic climate change since the mid-1990s, the research community has been arguing for the need for a large-scale, sustained Arctic observing system. These efforts have culminated in two initiatives: (1) the U.S.-led Study of Environmental Change (SEARCH), and (2) the European Union-led Developing Arctic Modeling and Observing Capabilities for Long-Term Environmental Studies (DAMOCLES). Both programs were timed to coordinate major efforts during the International Polar Year of 2007-2008 and are at present working to leave in place long-term observing systems. The U.S. effort is spearheaded by the NSF and has led to development of the Arctic Observing Network (AON). The AON primarily provides data from NSF-sponsored investigators. The Arctic Council has organized a project known as Sustaining Arctic Observing Networks, or SAON, which offers to help coordinate sustained observations and to serve as a data portal (www.arcticobserving.org). The naval forces would benefit from being involved with these planning efforts. FINDING 6.3: The Navy has billions of dollars in assets exposed to the threats of climate change, and it must make strategic decisions in the face of considerable uncertainty about the pace, magnitude, and regional manifestations of climate change. Yet Navy research at present has no capability for modeling the coupled ocean-atmosphere-land-cryosphere system and how it will respond to greenhouse gas forcing. The Navy also has no programs in seasonal-to-decadal timescale 29 Cecilia M. Bitz. 2008. “Some Aspects of Uncertainty in Predicting Sea Ice Thinning,” Arctic Sea Ice Decline: Observations, Projections, Mechanisms and Implications, E.T. DeWeaver, C.M. Bitz, and B. Tremblay (eds.), pp. 63-76. 30 Julien Boe, Alex Hall, and Xin Qu. 2009. “September Sea-Ice Cover in the Arctic Ocean Projected to Vanish by 2100,” Nature Geoscience, Vol. 2, pp. 341-343. 31 Cecilia M. Bitz, J.K. Ridley, M.M. Holland, and H. Cattle. 2010. “20th and 21st Century Arctic Climate in Global Climate Models,” in press in Arctic Climate Change—The ACSYS Decade and Beyond, P. Lemke (ed.).
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National Security Implications of Climate Change for U.S. Naval Forces climate forecasting to help guide long-range strategic planning for operations, platforms, and facilities; it relies almost entirely on civilian agencies and international assessments to inform its policies and practices related to climate change. RECOMMENDATION 6.3: The Assistant Secretary of the Navy for Research, Development, and Acquisition (ASN RDA) should examine the U.S. Navy’s overall research and development capabilities vis-à-vis climate studies, especially with respect to coupled models and climate forecasting on seasonal-to-decadal timescales. The ASN RDA should give special emphasis to regional aspects of sea-level rise, and sea-ice concentration and extent, because of their relevance to coastal infrastructure and operational needs. The Department of the Navy should also become actively engaged in the development of an Arctic Observing System, specifically with respect to development and deployment of in situ and remote sensing systems (i.e., gliders, buoys, and satellites) as well as icebreakers in support of research.