Over the past several years the U.S. intelligence community has engaged with the National Academy of Sciences and National Research Council (NRC) concerning a range of issues related to climate and security. A standing Committee on Climate, Energy, and National Security (CENS) was established in 2008 to facilitate the increased involvement of scientists in answering questions related to climate and environmental change, energy, natural disasters, and security. The committee undertakes activities to bring scientific expertise to bear on questions of importance to the intelligence community related to climate and environmental change (see, for example, National Research Council, 2010b, 2010d, 2012b). The CENS activities led to a request in 2010 for a study to, among other tasks, “identify ways to increase the ability of the intelligence community to take climate change into account in assessing political and social stresses with implications for U.S. national security.” The complete statement of task for this study appears in Box 1-1.
To carry out this task the NRC created a committee with broad expertise in the physical and social sciences and in security matters. The goal was for the committee to be able to integrate knowledge from across the physical and social sciences and also to be able to offer advice to the intelligence community on how to think about the security risks that might arise when climate change leads to situations for which countries, regions, or human life-supporting systems are not adequately prepared. Biographies of the committee members may be found in Appendix A.
This study focuses on some of the ways that climate change might create or alter risks to U.S. national security, in particular, ways that fall
Statement of Task: Assessing the Impact of Climate
Change on Social and Political Stresses
The National Research Council (NRC) would undertake a study to evaluate the evidence on possible connections between climate change and U.S. national security concerns and to identify ways to increase the ability of the intelligence community to take climate change into account in assessing political and social stresses with implications for U.S. national security. The study panel would focus on several broad questions, such as: What are the major social and political factors affecting the relationship between climate change and outcomes relevant to U.S. national security? What is the basis for this knowledge and how strong is it? What research and measurement strategies would strengthen the basis for this knowledge?
The study panel would develop a conceptual framework for addressing such issues on the basis of two workshops, existing research literature, and relevant NRC studies. It would produce a report including its conceptual framework and findings and conclusions regarding the key climate-security connections and issues of assessment of climate-related security risks examined in the workshops and the scientific literature. It would also identify variables that should be monitored and ways that indicators of climate change, impacts, and vulnerabilities might be developed and made useful to the intelligence community in assessing climate-related threats to U.S. national security.
within the mission of the U.S. intelligence community. This mission covers a broad range of risks. It includes possible military attacks on the United States, its allies and partners, and American facilities overseas, but it is much broader. The intelligence community is also responsible for assessing the likelihood of violent subnational conflicts in countries and regions with extremist groups, dangerous weapons, critical resources, or other conditions of security concern. It must also anticipate and assess various other risks to the stability of states and regions and risks of major humanitarian disasters in key regions of the world, both because of the indirect threats such risks may pose to the United States or its allies and because of national commitment to the principles of U.N. Security Council Resolution 1674, which proclaims “the responsibility to protect populations from genocide, war crimes, ethnic cleansing and crimes against humanity.”
Given these intelligence mission elements, the central questions motivating this study are: How might climate change lead to new or increased risks to U.S. national security? Might it, for example, put new stresses on societies or on systems that support human well-being, such as supply chains for food or energy, and thus pose or alter security risks to the United States? Will intelligence and security organizations need to gather
new kinds of information or synthesize existing information in new ways in order to assess climate-related security risks? Will they need to develop new ways to anticipate and assess security risks to address those that are affected by climate change?
This report is based on current understanding of the state of the climate system as assessed internationally by the Intergovernmental Panel on Climate Change (e.g., Intergovernmental Panel on Climate Change, 2007, 2012), as assessed nationally in reports by the U.S. Global Change Research Program (USGCRP) and by the NRC within the suite of congressionally mandated studies known as America’s Climate Choices (National Research Council, 2010a, 2010b, 2010c, 2010d) and in subsequent relevant reports (e.g., National Research Council, 2011a, 2011b, 2012b), and in other relevant literature reviewed by the committee. The committee’s purpose was not to readdress the science of climate change or to review past assessments, but to build on this knowledge to address the issues in the statement of task.
Over the past decade, several groups within the U.S. security policy community, both within and outside government, have given increasing attention to the potential risks that climate change could pose for national as well as international security. In 2008, for example, the intelligence community produced The National Intelligence Assessment on the National Security Implications of Global Climate Change to 2030 (Fingar, 2008).1 Climate issues were included in the 2010 Quadrennial Defense Review (QDR) (U.S. Department of Defense, 2010) as well as in the 2010 edition of the National Security Strategy (White House, 2010).
In addition to the attention from the U.S. government, beginning in the mid-2000s many foreign and security policy think tanks and research organizations produced reports on the potential connections between climate change and security. The reports were generally the work of groups of security experts, informed by consultations with climate scientists and regional and country specialists. Some reports also examined evidence from the social sciences. The groups drew upon this collective expertise to project a range of scenarios for potential impacts, usually over a 20-year period,
1 The assessment itself is still classified, but the methodology and principal conclusions of the report were presented in the statement for the record prepared in conjunction with testimony to the House Permanent Select Committee on Intelligence and the House Select Committee on Energy Independence and Global Warming. The National Intelligence Council also sponsored an extensive set of unclassified reports and conferences on the potential effects of climate change on key regions and countries; the materials may be found at http://www.dni.gov/index.php/about/organization/national-intelligence-council-nic-publications (accessed September 27, 2012).
although some also included projections to the end of the century. Given that these were not academic reports, the basis for the groups’ judgments and the level of confidence associated with them were usually not specified in detail. Without attempting a comprehensive review, this section seeks to provide a summary of frequently occurring themes and arguments about climate–security connections from major government reports (Fingar, 2008; U.S. Department of Defense, 2010; White House, 2010; Defense Science Board, 2011) and from some of the best-known examples in the mainstream policy literature (Busby, 2007; Center for Naval Analysis, 2007; Lennon et al., 2007; Center for Climate and Energy Solutions, 2009; Carmen et al., 2010; International Institute for Strategic Studies, 2011; Treverton et al., 2012). For some key statements from these studies, see Box 1-2.
These government and policy documents reflect a number of important common elements. Above all, the connections between climate and security are not presumed to be direct; they are seen as complicated and contingent, with the effects of climate events felt through their consequences for other factors that then affect security. For example, the 2010 QDR concludes:
While climate change alone does not cause conflict, it may act as an accelerant of instability or conflict, placing a burden to respond on civilian institutions and militaries around the world. In addition, extreme weather events may lead to increased demands for defense support to civil authorities for humanitarian assistance or disaster response both within the United States and overseas. (U.S. Department of Defense, 2010:85)
The most frequently cited potential climate events include sea-level rise, the shrinking of glaciers and the Arctic icecap, an increase in extreme weather events, and increasingly intense droughts, floods, and heat waves. The scenarios and examples presented in the above reports address broad consequences for fundamental societal needs such as food, health, and water and also the likely implications for specific regions and countries. Although the reports generally agree that future climate events are likely to increase tensions and political instability within and between states and perhaps also increase internal conflicts, they do not forecast an increase in interstate conflict.
Taken together, the most commonly cited climate–security scenarios in these reports result from failures or shortcomings of human systems in adapting to a changing climate; that is, they turn on the vulnerabilities of these systems to climate events. In these scenarios climate events cause harm to various support systems for human life and well-being by exceeding the ability of these systems to cope. Depending on other social, economic, political, and environmental factors, the harm may result in larger-scale political and social outcomes that are of concern for U.S. national security. All of the reports include some scenarios of this sort, although different re-
Statements About Climate and Security
Connections from Previous Security Analysis
“Climate change acts as a threat multiplier for instability in some of the most volatile regions of the world.” (Center for Naval Analysis, 2007:6)
“[T]he United States can expect that climate change will exacerbate already existing north–south tensions, dramatically increase global migration both inside and between nations (including into the United States), spur more serious public health problems, heighten interstate tension and possibly conflict over resources, challenge the institutions of global governance, cause potentially destabilizing domestic political and social repercussions, and stir unpredictable shifts in the global balance of power, particularly where China is concerned. The state of humanity could be altered in ways that create strong moral dilemmas for those charged with wielding national power, and also in ways that may either erode or enhance America’s place in the world.” (Lennon et al., 2007:103)
“We assess that climate change alone is unlikely to trigger state failure in any state out to 2030, but the impacts will worsen existing problems—such as poverty, social tensions, environmental degradation, ineffectual leadership, and weak political institutions. Climate change could threaten domestic stability in some states, potentially contributing to intra- or, less likely, interstate conflict, particularly over access to increasingly scarce water resources.” (Fingar, 2008:4–5)
“Since climate change affects the distribution and availability of critical natural resources, it can act as a ‘threat multiplier’ by causing mass migrations and exacerbating conditions that can lead to social unrest and armed conflict.” (Center for Climate and Energy Solutions, 2009:1)
“While climate change alone does not cause conflict, it may act as an accelerant of instability or conflict, placing a burden to respond on civilian institutions and militaries around the world. In addition, extreme weather events may lead to increased demands for defense support to civil authorities for humanitarian assistance or disaster response both within the United States and overseas.” (U.S. Department of Defense, 2010:85)
“Climate change is likely to have the greatest impact on security through its indirect effects on conflict and vulnerability.” (Defense Science Board, 2011:xi)
“Climate change is not happening in a vacuum: in many areas of the world it will be accompanied by rapid population growth, resource shortages, and energy price increases. Analytically, it is difficult to separate the effects of climate change from other factors, such as food shortages, migration, ethnic tensions and other issues that could drive violence. However, the potential impacts of climate change on water, energy, and agriculture will make it a central driver of conflict. The impacts of climate change combine to make it a clear threat to collective security and global order in the first half of the 21st Century.” (International Institute for Strategic Studies, 2011:11)
ports emphasize the effects of climate change on different support systems. Declines in food and water security are among the most frequently cited kinds of harm (e.g., Busby, 2007; Center for Naval Analysis, 2007; Lennon et al., 2007; Fingar, 2008; Center for Climate and Energy Solutions, 2009; Carmen et al., 2010; U.S. Department of Defense, 2010; Defense Science Board, 2011; International Institute for Strategic Studies, 2011; Treverton et al., 2012), and sub-Saharan Africa is often singled out as the region most likely to experience the greatest effects on security. For example, Fingar (2008) wrote:
We judge that sub-Saharan Africa will continue to be the most vulnerable region to climate change because of multiple environmental, economic, political, and social stresses…. Many African countries already challenged by persistent poverty, frequent natural disasters, weak governance, and high dependence on agriculture probably will face a significantly higher exposure to water stress owing to climate change. (p. 8)
In some of the scenarios increasing food and water insecurity interact to increase risks to health (e.g., Busby, 2007; Center for Naval Analysis, 2007; Lennon et al., 2007). In others health risks result from changes in weather patterns that shift the ranges for vector-borne diseases (Center for Naval Analysis, 2007; Lennon et al., 2007). Several scenarios see such declines in food or water security or disease outbreaks as likely drivers of population migrations, both within and across borders, that result in political or social stress, usually in the countries that receive the immigrant populations (e.g., Busby, 2007; Center for Naval Analysis, 2007; Lennon et al., 2007; Fingar, 2008; Center for Climate and Energy Solutions, 2009; Treverton et al., 2012). Two of the most-often cited scenarios are increased flooding or a rise in sea level forcing millions of Bangladeshis into India and an increasing desertification and drought forcing people from northern and sub-Saharan Africa into Europe. In both scenarios immigration issues are already a source of major tension. Energy security also figures prominently in several projected climate–security scenarios (Lennon et al., 2007; U.S. Department of Defense, 2010; International Institute for Strategic Studies, 2011), in which climate change is seen not only as yielding potential benefits for natural gas and perhaps biofuels producers but also as increasing the vulnerability of countries and industrial systems that rely on imported fuel (Lennon et al., 2007).
The paths envisioned from climate events to specific security consequences are often complicated. For example, tensions could increase over access to increasingly scarce resources, and that escalation, especially if it led to overt conflict, could in turn further limit access to resources so that people who had not previously been affected would now face shortages. Some scenarios suggest that diminished national capacity or outright state
failure would create increasing opportunities for extremism or terrorism. Again, sub-Saharan Africa is often cited as the most vulnerable region.
In addition to these specific scenarios, many of the reports foresee increasingly frequent and increasingly severe natural disasters that will strain the capacity to cope with the resulting humanitarian emergencies, both in the United States and overseas (Busby, 2007; Center for Naval Analysis, 2007; Center for Climate and Energy Solutions, 2009). This is of particular concern to the U.S. military, given its expanding role in disaster assistance, although several of the reports note that helping countries prepare for and cope with disasters offers important opportunities for positive engagement.
These climate–security analyses raise concerns about several security issues beyond those of inadequate adaptation leading to humanitarian disasters, political instability, or violent conflict. One class of scenarios involves direct threats of climate change to the ability of the U.S. military to conduct its missions. An example is the threat that sea level rise, possibly in combination with more intense coastal storms, poses to naval bases in low-lying coastal areas (Busby, 2007; Center for Naval Analysis, 2007; Center for Climate and Energy Solutions, 2009; U.S. Department of Defense, 2010).2 More generally, analyses foresee climate change having broad negative effects on military organization, training, and operations—for example, by exacerbating operational difficulties for troops and equipment in already difficult locations (Busby, 2007; Center for Naval Analysis, 2007; Center for Climate and Energy Solutions, 2009; Carmen et al., 2010; U.S. Department of Defense, 2010; National Research Council, 2011b). Other concerns include the vulnerability of U.S. Department of Defense (DOD) fuel supplies to severe weather that disrupts supply lines and the possibility of droughts restricting access to water for forces and facilities overseas.
Perhaps the most frequently cited security risk from climate change is the possibility of melting Arctic sea ice leading to increased international tensions over newly accessible sea routes and natural resources in the Arctic (Busby, 2007; Center for Naval Analysis, 2007; Carmen et al., 2010). A recent NRC study (National Research Council, 2011b), addresses these and other security issues of interest to the U.S. naval forces.
It is now clear from an accumulation of scientific evidence that the risks of potentially disruptive climate events are increasing. The scientific evidence on this point is aptly summarized in this conclusion from a recent major review of the science by the NRC: “Climate change is occurring, is
2 For examples of the severe damage suffered by U.S. bases in the past from hurricanes, see Busby (2007:6).
caused largely by human activities, and poses significant risks for—and in many cases is already affecting—a broad range of human and natural systems” (National Research Council, 2010a:3). These increased risks will not be reduced anytime soon: “Human-induced climate change and its impacts will continue for many decades and in some cases for many centuries. Individually and collectively, these changes pose risks for a wide range of human and environmental systems, including…national security” (National Research Council, 2010a:4). Moreover, many of the forces driving anthropogenic climate change, chiefly emissions of carbon dioxide and other “greenhouse gases” and changes in land use that increase net absorption of energy from the sun, have been increasing at an accelerating rate over the past century or so (National Research Council, 2010a). Accordingly, global average temperatures have been increasing substantially over the past century (NASA Goddard Institute for Space Studies, 2012), and, given the long residence time of carbon dioxide within the atmosphere, further temperature increases are projected for at least the rest of the current century even under scenarios in which past emissions trends are significantly curtailed (Meehl et al., 2007). As another recent NRC report pointed out, “Recently experienced climatic events are not likely to serve as guides to what to expect next” (National Research Council, 2009:14).
In short, it is becoming increasingly likely that the world will experience climate-related conditions it has not seen before. The frequency of natural disasters related to weather and climate has been increasing for at least three decades, as have losses from these events (Intergovernmental Panel on Climate Change, 2012; Munich Re, 2012). Temperature trends at the local level show both increasing average temperatures and increasingly frequent occurrences of high temperatures that were quite rare in the 1951–1981 period (see Figure 1-1). As discussed further in Chapter 3, temperature increases have implications for the hydrological cycle because for each 1°C in global mean surface temperature there is a corresponding 7 percent increase in atmospheric water vapor.
These trends indicate that high-temperature extremes are becoming more common even more rapidly than the average temperature is increasing and that the rate of change is increasing. Such trends in extreme events and the current understanding of climate change provide ample reason to expect these weather and climate trends to continue, along with the considerable spatial and interannual variability that has been experienced in the recent past. Presently, the ratio of record daily high temperatures to record low temperatures at U.S. observing stations is 2 to 1, rather than the 1:1 ratio that would be expected if climate were not warming. For a mid-range emission scenario, the ratio has been projected to increase to 20 to 1 by mid-century and to roughly 50 to 1 by the end of the century (Meehl et al., 2009).
The 2009 NRC report appears to have been prescient in making this observation: “[D]ecision makers must expect to be surprised—probably with increasing frequency” (National Research Council, 2009:18). An important reason to expect to be surprised is that Earth’s climate is changing at a rate that is unprecedented, at least throughout human history. The rate of carbon dioxide buildup in the atmosphere is now a factor of 10,000 greater than it was during any period on geological record prior to human civilization, and sea levels during prior interglacial periods with comparable average surface temperatures were substantially higher than they currently are (Hansen et al., 2010). The unprecedented rate of carbon dioxide accumulation means that Earth’s climate system—and likely its ecological
system as well—will continue to undergo a very large energy balance adjustment, possibly at an unprecedented rate. One can confidently expect that there will be significant consequences. Although we do not know the exact magnitude, timing, or character of all of these consequences, it is prudent to assume that some of them will appear as surprises in the form of unanticipated events that compel some reaction.
National security decision makers do not like surprises and expect the intelligence community to provide sufficient warning to make it possible to avoid, ameliorate, or alter the undesired consequences of emerging developments. Fundamental knowledge of climate dynamics indicates that many types of extreme climate events are likely to become more frequent, even though we do not know enough to predict which extreme events will occur where or when. Although it is true that old climate averages are not a good guide to the future, recent experiences of climate-driven surprise are likely to be a good guide to what to expect next. In Chapter 3 we discuss in more detail what climate science can and cannot tell us about what events to expect in the future.
From the standpoint of those who must deal with the consequences of any specific climate-related event, it may make little difference whether the event can be reliably attributed to anthropogenic climate change or whether it instead results from natural climate variation. But from the standpoint of anyone concerned with the global profile of security risks, it is important to recognize that such events are expected to become more common because of anthropogenic climate change. Whether any specific event can be attributed to anthropogenic climate change is less relevant than the likelihood of serious climate-related disruptions occurring in places where they might raise security risks for the United States and the change in that likelihood over time. Security analysis must be based on an accurate assessment of the risks, and the risks from climate events are changing. It is also worth noting that many other countries are contemplating—or taking, or want to take—steps to address the emerging risks of climate change. This provides a basis for cooperative action on reducing these risks as well as a reason to regularly reassess vulnerabilities to the effects of climate change.
What “Climate Change” Means in This Study
Climate change is commonly defined by climate scientists as change in the mean or variability of a climate property that persists for an extended period, typically a decade or longer (Intergovernmental Panel on Climate Change, 2012). In this study we are interested in both climate change and climate variability. Climate variability refers to variations from the mean (and other statistical properties) of the climate at all spatial and temporal scales beyond that of individual weather events. (Definitions adapted from
Intergovernmental Panel on Climate Change, 2012.) Among the various types of climate variability we are particularly interested in those variations, such as the El Niño–Southern Oscillation, the North Atlantic Oscillation, and others, that have effects for multiple years and for which early warning is possible.
We include both climate change and climate variability because it will generally be climate events, particularly events now considered extreme, which will lead to various security-related issues. Normal climate variability has in the past led to a few such extreme climate events, but these events can be expected to become more frequent with climate change. As we discuss in Chapter 3, the combination of climate change and climate variability will further alter the frequency of such events. These climate events can be politically and socially disruptive and may require U.S. government action independent of whether or not particular events can confidently be attributed to anthropogenic climate change.
Thinking About Unlikely Extreme Events
Occasions in which climate change may contribute to events requiring U.S. government action may arise in the context of climate surprises or as the result of the conjunction of climate events and social or political developments. The contributing climate events are typically extreme events and therefore, by definition, have been highly unlikely in the past. They may either be acute (e.g., a storm) or slowly developing (e.g., a drought). After such events occur it is often easy to identify the relevant precursors, but before the event it is often much more difficult to separate the signal from the noise. When considering the relationships of climate change to national security before the occurrence of such events, intelligence analysts need ways to decide which of the many unlikely events that could contribute to a crisis are most worthy of attention.
It is important to recognize that climate scientists and security policy makers tend to have very different ways of thinking about unlikely events. This is particularly the case with extreme climate events, which have been quite infrequent but can also be highly consequential. Although extreme events have the greatest potential to disrupt political and social systems and raise security concerns and are thus the most important events for security analysts to understand, their low frequency of occurrence makes it especially difficult to validate scientific predictions about them.
Scientists tend to be conservative in making claims about the future because of their usual rules of inference. In making projections about the climate future, especially of unlikely events, scientists develop and validate complex models and test them by attempting to reproduce documented climate trends and events. They typically initialize models with obser-
vational data beginning at some point in the past and test retrospective model predictions (i.e., hindcasts) against known observations between the initial point and the present. To the extent that understanding can be demonstrated by this method, they then project future climate based on assumptions of future greenhouse gas concentrations that are predicated on scenarios of economic growth, energy consumption, and demographic change, carefully noting the uncertainties in the projections. If projections using several different models tend to agree, scientists’ confidence in the results increases.
This approach has certain limitations, particularly in dealing with highly infrequent and unprecedented events. For such events there are relatively few data with which to build the models and test them against past experience, and, as a result, models that make slightly different assumptions can lead to different projections of the future likelihoods of those events. When this happens, scientists’ confidence in projections is low, and they are reluctant to make statements about the future likelihood of such events. This may not mean that such events can safely be considered to be highly unlikely, but only that there are not enough data to make a confident projection of likelihood.
It is in the nature of the scientific enterprise that claims are not made about the existence of phenomena unless a high level of confidence can be asserted for such claims. A 95 percent confidence level is a typical cut-off point: Scientists defer making claims or predictions until they can be highly confident in them. In short, science requires a high burden of proof for concluding that a climate phenomenon exists or that a projection of future climate conditions—especially extreme conditions—is solidly supported.
In security policy the practice for deciding whether to take a hazard seriously is much different from the practice in making scientific claims. Security analysts are focused on risk, which is usually understood to be the likelihood of an event multiplied by the seriousness of the consequences if it should occur. Thus security analysts become seriously concerned about very high-consequence negative events even if scientists cannot estimate the probability of their occurrence with confidence and, indeed, sometimes even if they are fairly confident that the probability is quite low. During the Cold War, for example, most people thought that deterrence was robust, and few thought the likelihood that the Soviet Union would actually initiate a nuclear attack against the United States was anything but minuscule. But because the consequences would have been so dire, tremendous efforts were made by the intelligence and national security communities to monitor events that might provide early warning of the possibility of such a strike. The same is true of threats of terrorist attacks on the U.S. homeland today. Even though there have been few terrorist attacks altogether—and no major ones on the United States since 2001—substantial resources
are allocated to identifying threats and reducing risks. The public and elected officials have consistently supported such risk-based allocations of resources.
Unlikely Extreme Events in an Unprecedented Climate
From the perspective of security, events that could disrupt the social and political systems of importance to U.S. national security are particularly important. Certain climate events—most likely, rare and extreme events— could meet this criterion. These are, by definition, events on the long tails of the probability distributions of climate events. Unfortunately, the climate science community is much less confident in its skill at projecting the rate of change in the frequency or magnitude of events at the extremes of such distributions than it is in projecting averages or even the likelihoods of events in the middle 80 to 90 percent of the distributions. One reason for caution is, as already noted, that there is a very limited population of such events to use for validating models. Moreover, the spatial resolution of climate change models is often coarser than is required to resolve the spatial structure of many extreme events to the degree needed for security analysis.
Another factor limiting confidence in the projections of extreme climate events is that the fundamental attributes of Earth’s climate system have moved or very soon will move beyond the bounds of experience on which models are based. For example, the concentrations of greenhouse gases (GHGs) in the atmosphere are now greater than they have been for at least 800,000 years (National Research Council, 2010a), and the current rate of carbon dioxide accumulation in the atmosphere is at least an order of magnitude greater than the natural rate that prevailed prior to the rise of human civilizations (see http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_co2.html [accessed November 14, 2012]). As climate moves outside the range of experience, models of the effects of higher GHG concentrations cannot be validated against the kinds of high-resolution observational data that provide the most desirable basis for model testing. Global average temperature already is or soon will be higher than it has been at any time in recorded human history, and it is increasing at an unprecedented rate (Intergovernmental Panel on Climate Change, 2007; National Research Council, 2009). Moreover, the variance in temperature indicators has been increasing over the past half century (see Figure 1-1). All of these phenomena—higher temperatures, higher variation in temperatures, and rapid change—increase the likelihood of the occurrence of extreme temperature events. In addition, as the climate moves outside the bounds of the experience on which existing models are validated regarding the averages and ranges of variation of climate parameters and their rates of change, scientists may attach less confidence to projected extremes simulated by the models.
Unprecedented rates of change in the global average temperature and in the GHG concentrations that drive this change are particularly challenging for the climate modeling enterprise because of the well-known fundamental properties of complex systems, of which Earth’s climate is a paradigmatic example. Because of the state and rate of change of Earth’s climate over recent decades, confident projections of extreme events are especially difficult to produce. This does not mean that climate science has nothing to say about the future of extreme events that can be useful to the intelligence community. What it means is that there are multiple scenarios of the future of climate events that are each likely enough that they deserve consideration by the intelligence community. They should not be treated as predictions but rather as possibilities for evaluation in terms of the social and political scenarios they might set in motion, the security issues that might ensue, and the preparedness of the U.S. government to deal with the consequences.
Fundamental climate science provides some useful concepts for thinking about the future of climate events despite the limits of predictability of particular events. Consider, for example, the implications of the fact that although Earth’s temperature remains well above the long-term average, the decade beginning in 1998 represented a hiatus in the longer overall global warming trend (National Aeronautics and Space Administration, 2012). A fundamental understanding of Earth’s climate system makes it clear that global warming has not stopped and that the hiatus will be brief. The past two years suggest that it may already have ended (Foster and Rahmstorf, 2011; National Aeronautics and Space Administration, 2012).
The past 130 years or so include periods with strong warming and periods with little or no warming (e.g., Easterling and Wehner, 2009). As we discuss further in Chapter 3, even under continuing climate change decades with no warming can be expected in the future—along with decades with above average rates of warming. The coupled climate system has naturally occurring decadal signals, such as the Pacific Decadal Oscillation and the Atlantic Multi-Decadal Oscillation, which can serve to mask or accelerate the average rate of warming on decadal time-scales. The underlying trends can be understood in relation to fundamental processes of energy balance: If the climate system is continuing to absorb more energy from the sun than it is emitting, as must happen when greenhouse gas concentrations are increasing, then that energy remains in the Earth system and must show itself sooner or later through increased temperatures along with other changes in the climate system. Recent research (Meehl et al., 2011) suggests that during the hiatus in recent years most of this excess energy has gone into the deep oceans, where it may show itself through the enhancement of coupled oceanic-atmospheric phenomena, such as a strong El Niño and warming ocean temperatures.
Analyzing Plausible Extreme Event Scenarios
Climate scientists have paid significant attention to some of the ways that gradual global climate change might lead to abrupt and sometimes irreversible large changes at a continental or regional scale (National Research Council, 2002; Alley et al., 2003; Lenton et al., 2008). None of these possibilities can be projected with a level of confidence that would satisfy climate scientists. However, from a security analysis standpoint, in which attention is paid to future scenarios that are of sufficiently high consequence even if their probabilities are relatively low, this scientific work points to particular possible extreme event scenarios that are worthy of further analysis.
An example of the kind of process that could lead to surprising and very extreme events can be drawn from evidence in the paleoclimate records combined with recognition of enhanced polar temperature variations due to changes in GHG concentrations. Citing an observation by Bintanja et al. (2005) that over the past 800,000 years a 1°C increase in global mean temperature was associated with increased equilibrium sea levels of about 20 meters, Hansen and Sato (2012) have suggested that the sea level rise in the next century may well be on the order of 5 meters. They argue that an increase of 3.6°F (2°C) over pre-industrial temperature levels, which is highly likely to occur in this century, would commit the planet to sea level rise of many meters. Given the considerable uncertainty in the science of glaciology about the stability of major ice sheets, it is unclear whether their contribution to sea level rise over the next century will be linear or will follow a nonlinear trajectory with an increasing rate of change over time. If nonlinear processes prevail, then the common projection of up to 1 meter by the end of the century may be a lower bound rather than an upper bound. The rate at which the sea level rise would occur is critically important, of course, in terms of the social and political consequences.
To better evaluate the import for U.S. national security of scenarios like this, which have some scientific plausibility but which extend beyond the current scientific consensus, the intelligence community might benefit from several types of knowledge that could be developed in the coming decade to help analysts anticipate security issues that might arise if such a scenario is realized. These would include improved measures of rates of change in temperature and glacier ice cover in the polar regions; the use of existing climate models to project how this degree of ice melting would affect such outcomes as coastal inundation, extreme precipitation, and cyclonic storm severity; and assessments of the exposure, vulnerability, and response capacity of key countries and regions to these outcomes.
Several other examples of potential rapid-onset extreme climate event scenarios can readily be found (Lenton et al., 2008). For instance, models of changes in the Indian summer monsoon indicate that several sharply dif-
ferent but potentially dangerous shifts in the intensity of the monsoon are plausible, with the changes possibly occurring with a transition time of only a year or so. From a security perspective it may make sense to take each of the model-projected futures through a what-if scenario mode. Similarly, projections of the West African monsoon point to a Sahel (the east–west stretch of Africa south of the Sahara desert and north of the Sudanian savannahs) that is either wetter or drier or else has no average change in rainfall but has a doubling of the number of anomalously dry years (Lenton et al., 2008)—three scenarios that could be examined in terms of their social and political implications.
The purpose of this study is to help improve the ability of the U.S. intelligence community and other interested actors to foresee security risks that may arise from climate change and its interactions with other social, economic, and political processes. Thus, we are concerned with climate risks to the extent that they may affect security risks.
Improved foresight can inform several kinds of policy responses: (1) responses to reduce climate risks (i.e., the risks that potentially harmful climate events will occur); (2) responses to reduce the exposure of people or valued assets to potentially harmful climate events; (3) responses to reduce susceptibility to harm from such events; and (4) responses that assist in the coping, response, and recovery processes after harmful events occur. We are aware of debates about how such policy responses should be organized and by whom. These questions are beyond the scope of our study, as are questions about how best to reduce the risks of occurrence of harmful climate events. Our focus is on anticipating security risks related to climate processes, understanding the roles of climatic and other factors in the dynamics of these risks, and informing decision makers about the nature of these risks and the opportunities for reducing them. We hope the study will, by improving understanding of the risks, provide a better basis for informed debate about which policy responses are most advisable. We have focused the study in three important ways, as outlined below.
Focus on Vulnerability to Climate Events
Although each of the scenario types that have been mentioned in climate–security studies is potentially significant for national security, this study focuses on scenarios involving the vulnerability of human populations, institutions, and life-supporting systems to harm from climate events, in which the harm has the potential to set events in motion that lead to security concerns. As discussed above, these scenarios in which climate events
cause sufficient harm to human well-being to create humanitarian crises, political violence, or other issues of security concern are among the most prominently cited in the reports on climate change and security that have appeared in recent years from U.S. government security agencies and the foreign and security policy community. Such vulnerability-based scenarios predominated among the sponsor’s concerns in requesting this study and in the early deliberations of the committee in open session with the sponsor present. The committee decided at the outset that these concerns provided the most appropriate focus for its work, as is discussed in further detail when the conceptual framework is presented in Chapter 2.
We acknowledge that with this focus, this study sets aside some climate–security connections that could prove highly significant and that deserve further study and analysis. These include some potential threats already noted, such as from extreme climate events that may impede the ability of U.S. military organizations to perform their missions and from conflict over natural resources and sea lanes in Arctic regions that may become newly accessible as a result of the melting of sea ice (cf., National Research Council, 2011b).
Another important class of security risks that are excluded from this study is those that may arise from policy responses to the anticipation or experience of disruptive climate events. Several plausible security risk scenarios begin with policies to limit climate change. For example, the expanded use of nuclear power in some countries to replace fossil fuels could increase risks of nuclear proliferation. Some policies to increase biofuel production could contribute to food price spikes and thus reduce effective food availability to low-income populations around the world. A single country’s decision to counter global warming by geoengineering, perhaps by fertilizing the ocean to grow photosynthetic organisms or by injecting sulfate particles into the stratosphere, could create conflict with other countries. Several other policy-based scenarios begin with a country’s efforts to protect itself from the expected consequences of climate change in ways that could disrupt international relations. For example, an upstream country might impound water from a river to guard against drought and thus reduce water supplies for its downstream neighbors. Or one country might purchase land in another country to produce food for its domestic consumption, creating conflict if a future food shortage hits the country where the food is being produced for export.
A number of threat scenarios of the above types are mentioned in previous climate–security analyses. Although some of them could have significant security consequences, they have not been treated as primary concerns in these reports. We have focused more narrowly on situations in which direct harm from climate events affecting vulnerable places or critical life-supporting systems could play a driving role in events of security
concern. Policy responses intended to reduce one nation’s vulnerability to climate events may sometimes increase the vulnerability of other countries. These kinds of climate-security connections could prove highly significant and deserve serious attention in security analysis, both by monitoring the development of such policies and by analyzing their implications for stresses in other places both when they are put in place and when a stressful climate event subsequently occurs.
Focus on Disruptions Outside the United States
Our study focuses largely on developments and vulnerabilities external to the United States, while recognizing that climate change is a global phenomenon and that events occurring within the United States can be disruptive in other countries, and vice versa. We examine some of these connections but not others. For example, a drought in U.S. agricultural areas that led to a spike in the global price of corn or wheat could lead indirectly to a humanitarian or political crisis elsewhere that could become a national security issue for the United States. Our study does examine such scenarios, but it does not examine the social and political consequences such events might have within the United States, nor does it examine the social and political consequences within the United States of climate events occurring elsewhere that disrupt global systems such as public health or the supply systems for critical commodities.
We emphasize, however, that such a separation between domestic and foreign impacts reflects only the division of missions among federal agencies, not the characteristics of climate phenomena or their consequences. In particular, observations, analyses, and fundamental knowledge that need to be developed in order to understand changing vulnerabilities to harm from climate events, which can offer valuable information to the U.S. intelligence community, are equally important for informing other federal agencies and decision makers below the national level, particularly including agencies responsible for domestic security and disaster management. They are also critical for informing international organizations. In Chapter 6 we discuss the needs for monitoring and analysis within a whole-of-government approach to developing an understanding of the effects of the changing risks of climate events.
Focus on the Next Decade
Given the risks and difficulties of projecting political, economic, and technical developments more than a decade into the future and the fact that countries are—and should be—starting now to contemplate steps to reduce vulnerability to climate change effects, this study focuses primarily on the
next decade. In this way the study differs from most past analyses of climate change and its security implications. We consider policy and intelligence-gathering actions related to events that might occur in the coming decade as well as activities that must begin within a decade in order to have adequate intelligence capacity for anticipating climate–security interactions at later times. An adequate intelligence capacity in this area must include an improved ability to anticipate changes in climate-related security risks beyond the decadal time horizon, for at least two reasons: The processes of climate change already in motion will most likely have their more serious security impacts beyond the next decade, and actions taken within the decade can reduce those longer-term risks.
Implications for Security Analysis
Policy makers can pay attention to only so many warnings. The purpose of this report is to help intelligence analysts determine where to focus and how much attention to pay to the less likely, but potentially significant, developments for security that might result from climate change. This study does not offer recommendations on where or when the U.S. government should act on risks related to climate change. That is a policy choice that will depend on much more than the risks of climate events—or even the risks of humanitarian crises, political instability, violent conflict, or other extreme social or political events that may be influenced by climate change. Rather, the focus of this study is on offering ways to better assess such risks and to anticipate changes in them.
The next chapter presents the conceptual framework for the project, laying out the key concepts and relationships that provide the structure for analysis. It considers risks as resulting from climate events; exposures of people, places, or important life-supporting systems to these events; vulnerability to these events (susceptibility to harm and the likelihood of effective coping, response, and recovery); and social and political disruptions that may result from responses to these events that are or are perceived to be inadequate. That framework is used in the next three chapters to examine current knowledge about the potential links between climate change and political and social stresses with implications for U.S. national security. Chapter 3 focuses on climate events. It considers what kinds of potentially disruptive climate events can be expected, especially in the coming decade, as a result of climate change. Chapter 4 examines changing exposure and vulnerability to potentially disruptive climate events and takes up the question of what kinds of connections exist between climate events and vulner-
ability as well as examining processes of coping, response, and recovery after an event. Chapter 5 considers security risks that have been linked to climate change in previous studies and explores the question of what links, if any, exist that connect climate change to political and social stresses and thus to outcomes of obvious security concern, such as violent conflict, pandemics, or disruptive migration. It addresses a continuing discussion in the academic literature about direct versus more complex and contingent relationships. These chapters provide the evidence to support the work in Chapter 6, which takes up a core task of the project: recommending what the intelligence community should be monitoring in order to assess climate– security connections in ways that are useful for policy.