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Adapting to the Impacts of Climate Change (2010)

Chapter: 4 Managing the Climate Challenge: A Strategy for Adaptation

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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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Suggested Citation:"4 Managing the Climate Challenge: A Strategy for Adaptation." National Research Council. 2010. Adapting to the Impacts of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12783.
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CHAPTER FOUR Managing the Climate Challenge: A Strategy for Adaptation A s the previous chapter demonstrates, many ideas are available about ways to adapt to climate variability and change. However, few of these options have been assessed for their effectiveness under projected future climate condi- tions and how they might interact across the sectors and with other stressors. In addition, effective planned adaptation is hampered by a number of challenges and barriers, and there is a need for a comprehensive approach to adaptation planning to overcome them. In the face of both limited knowledge on adapting in the context of climate change and the importance of addressing climate change risks in a prudent and timely manner, a process is needed that allows decision makers to identify and address the most urgent risks and incorporate new information and knowledge in the decision-making process in an iterative fashion. This chapter reviews the challenges and barriers and suggests some approaches to choosing among the many options to manage the risks associated with climate change, using the example of New York City’s recent adaptation activities. THE ADAPTATION CHALLENgE Despite the nation’s substantial economic assets, at present its adaptive capacity to respond to new stresses associated with climate change is limited. As a starting point, it can be argued that our societies are not even well adapted to the existing climate, especially to well-understood natural hazards (hurricanes, floods, and drought) that continue to result in human disasters (Mileti and Gailus, 2005; NRC, 2006; O’Brien et al., 2006). Numerous reports and academic research papers describe long-standing impediments to natural hazards mitigation, and these challenges will continue to limit our capacity to adapt to climate change—especially when it involves the intensifica- tion of natural hazards (NRC, 2006). Adaptation requires both actions to address chronic, gradual, long-term changes such as ecosystem shifts and sea level rise, and actions to address natural hazards that may become more intense or frequent. Addressing gradual changes is challenging be- 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E cause the eventual extent of such changes is difficult to recognize and measure, plans beyond 20 years are usually met with skepticism, and costs for initial investments may be unaffordable even when cost-effective in the long term. The experience of New Orleans with Hurricane Katrina—and in fact, continued development throughout the nation in hazardous areas that increase exposure to coastal storms, flooding, and wildfires—indicates a need for fundamental changes in the management of climate- sensitive resources such as coastal areas regardless of the intensification of hazards due to climate change. The continued development of vulnerable areas such as those prone to flooding increases climate risks. Climate changes such as sea level rise and increased storm intensity further exacerbate climate risks, bringing new urgency to these issues. Existing recommendations for improvements in natural hazards manage- ment (Heinz Center, 2000; NRC, 2006) should be considered very seriously since many of these actions would address the most immediate needs for climate adaptation as well. Political Impediments For several decades, climate change adaptation has been neglected in the United States, perhaps because it was perceived as secondary in importance to mitigation of greenhouse gas (GHG) emissions, or perhaps more importantly because it would actually take attention away from mitigation by implying that the country can sim- ply adapt to future changes (Adger et al., 2009; Moser, 2009b). In addition, the topic of climate change and the discussion of options for responding have become much more highly politicized in the United States than in some other parts of the world. Arguments in the media over whether climate change is “real” and to what degree it is a problem generated by human activity have confused people about whether action is needed and whether their actions can make any difference (Boykoff, 2007). Further- more, there are frequent suggestions in the media that responding to climate change is “too expensive” or that the options available to limit emissions and adapt to impacts will have a negative impact on the U.S. economy. Adaptations to long-term problems involve long-term investments and bring consid- erations of intergenerational equity and other social and economic factors into play that significantly affect the calculation of costs and benefits. The influences of climate change extend well beyond the election cycle of the typical public official in the United States. Long-term adaptations must, therefore, hold some promise of short- term reward if they are to be attractive to elected decision makers. 

Managing the Climate Challenge Institutional and Resource Limitations Several reports have found that current U.S. institutions at virtually every scale lack the mandate, the information, and/or the professional capacity to select and implement climate change adaptations that will reduce risk sufficiently, even when these adapta- tion actions are urgently needed (Moser, 2009b; NRC, 2009a,b). New institutions and bridging organizations will be needed to facilitate the communication and integrated planning required to address complex intersectoral problems that cross geographic scales (ACC: Informing an Effective Response to Climate Change; NRC, 2010a). Moreover, the availability of funding for climate change adaptation at most levels of government has been highly constrained, and there are few public-sector entities that have identi- fied resources for adaptation (NRC, 2009a). Identifying new financial resources that can be directed toward adaptation might be difficult in any case, but it is particularly challenging as the world’s major economies struggle to recover from the worst recession in decades. The vagaries of economic cycles and the associated political volatility make it clear that adaptation efforts need consistent sources of funding over time because “stop-and-go” efforts are far more ex- pensive and far less effective. Mainstreaming adaptation considerations and outcomes into decisions with climate-sensitive consequences (such as reauthorization of laws af- fecting land and water use, the National Flood Insurance Program, or the Coastal Zone Management Act) is one way to reduce cost, provide incentives to adaptation, and perhaps smooth the intensity of adaptation efforts (see Box 4.8 later in this chapter). Notwithstanding efforts to reduce costs, the total expenditures on adaptation will most likely have to be substantial and grow over time. There is very little reliable source material, however, on the total financial costs of adaptation, particularly for the United States. To be sure, some studies apply uniform and, in many cases, simple rules to estimate how societies will adapt and the cost of such adaptations. Such a “top- down” approach often does not sufficiently account for geographic variation in vulner- abilities, adaptations, and costs, and it usually fails to distinguish between voluntary and policy-driven adaptation. Some recent studies have attempted to estimate either global costs of adaptation or total costs for developing countries. For example, the United Nations Framework Convention on Climate Change (UNFCCC, 2007) estimates annual costs of $49 to $170 billion for global adaptation by 2030, and the World Bank (2009) estimates annual costs of $75 to $100 billion by 2050 in developing countries alone. Parry et al. (2009) concluded that the UNFCCC (2007) estimate may be too low by a factor of 2 to 3. 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E The literature does not contain comprehensive estimates of adaptation costs in the United States, but early estimates for some sectors have been published. For example, it has been estimated that the cumulative infrastructure costs of protecting low-lying coastal areas in the United States from up to a 3-foot sea level rise could reach more than $100 billion (Neumann et al., 2000), which avoids even larger losses to property and land values. The cumulative costs of adapting water resource infrastructure to cli- mate change in 2050 are estimated to be half a trillion dollars (CH2MHill, 2009). These studies suggest that the annual financial costs of worthwhile adaptation in the United States could be tens of billions of dollars by midcentury. Although the lack of funding is a much more serious concern in developing countries, it is clear that the United States has failed to properly maintain existing water, waste- water, transportation, and energy infrastructure even for the climate that it faces now (see AWWA, March 2009,1 estimates of infrastructure repair needs). As a result, there is already an “adaptation deficit.” The need to cope with a dynamic climate that will pose new threats over time only adds to the challenge and will most likely increase the costs of investing in infrastructure. MANAgINg THE RISK Adaptation is fundamentally a risk-management strategy. Risk is a combination of the magnitude of the potential consequences and the likelihood that they will occur. Managing risk in the context of adapting to climate change involves using the best available social and physical science to understand the likelihood of climate impacts and their associated consequences, then selecting and implementing the response options that seem most effective. Because knowledge about future impacts and the effectiveness of response options will evolve, policy decisions to manage risk can be improved if they incorporate the concept of “adaptive management,” which implies monitoring of progress in real time and changing management practices based on learning and as a recognition of changing conditions (ACC: Informing an Effective Response to Climate Change, NRC, 2010a; NRC, 2009a; NRC, 2004) is incorporated. The National Research Council (NRC, 2009a, p. 76) report states, “Rather than presuming that managers make one-time decisions on the basis of the best existing knowledge, 1 The U.S. Environmental Protection Agency’s quadrennial assessment now estimates that $334.8 billion needs to be spent over the next 20 years on drinking water infrastructure needs. The American Society of Civil Engineers (ASCE) 2009 Report Card for America’s Infrastructure, which gave drinking water and waste- water infrastructure a grade of D−, cited investment needs totaling around $1 trillion for both water and wastewater over the same period. ASCE estimates the funding shortfall on drinking water projects alone will be $11 billion annually. 

Managing the Climate Challenge adaptive management regards policy choices for complex environmental problems as part of a carefully planned, iterative, sequential series that emphasizes monitoring and learning as the system changes, both in response to external stimuli and in response to managers’ actions.”2 This section proposes a framework to manage the risk associated with the impacts of climate change on the natural and built environments. The framework includes (1) identifying the key problems and asking the right questions, (2) assessing the risk, (3) perceiving the risk, (4) properly communicating risk to decision makers, and (5) de- signing and implementing risk-management strategies. Identifying the Problems and Asking the Right Questions It is important to be clear at the start about the problem to be managed. Without a shared understanding of the nature of the problem, the desired goals of the stake- holders, and the “decision context” (Jacobs et al., 2005), collective risk management is not likely to be successful. In framing the problem, it is important to include the perspectives of individuals and interested parties whose voices and concerns might not otherwise be heard, those who will assume the responsibility of administering and implementing the adaptation and sustaining it over time, and those involved in monitoring success or failure against stated goals and objectives. In coping with uncertainty, it will be particularly important to separate relevant signals from random noise in the observations, carefully analyze new scientific information, and design “midcourse” adjustments based on lessons learned. For example, when developing adaptation measures to reduce the impact of sea level rise on damage to coastal areas from floods and hurricanes, key interested par- ties should include the relevant public- and private-sector agencies concerned with climate change impacts, businesses that will develop technology or approaches to adaptation, those who are vulnerable economically and physically (e.g., adverse health or environmental effects), and those who will have to pay for adaptation measures and deal with the adverse impacts from global warming. 2 It is important to note that “adaptive management” is used here in its most general form. It implies an iterative process in which decisions are based on evolving understanding of the underlying natural and social science and the observed success (or failure) of programs and policies that have been implemented. The panel is not using the Holling (1978) framework, in which policies and programs are viewed as experi- ments designed to elicit new information. 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E Assessing Risk In the context of climate adaptation, assessing risk means identifying specific (climate- related) events and evaluating their potential adverse (and in some cases beneficial) consequences in terms of magnitude, spatial scale, time frame, duration, intensity, and consequences for society. Risk as assessed by experts encompasses studies that estimate the chances of a specific set of events occurring and/or their potential con- sequences (Haimes, 1998). The primary goal of assessing risk is to produce information that improves risk-management decisions and to identify and quantify the impact of alternative actions (including the status quo) and their consequences. Assessing risk may also include considering the nature of vulnerabilities and consequences associ- ated with specific risk-management decisions. Once the problem is well identified, assessing risk begins with hazard identification— the process of specifying the scope of the assessment. In the case of climate change, the available empirical evidence can be summarized with respect to its potential impacts on natural and social systems and different economic sectors, including interactions between sectors and systems. In some cases, these impacts can be associ- ated with specific climate futures (high, medium, and low emissions over time, with or without efforts to limit atmospheric GHG concentrations). Other scenarios can be based on emissions trajectories with distributions of impacts over time. In either case, the process of assessing risks will vary depending on the sector being examined and the interests and concerns of affected stakeholders. Scenario analysis is a widely used technique for identifying vulnerabilities from cli- mate change (see Mearns and Hulme, 2001). In some cases, the relative likelihoods of alternative futures can be supported using risk-based techniques such as expected cost-benefit analysis and decision analysis, including expected value of information and efficient risk-spreading designs (e.g., insurance). In other cases, several scenarios (e.g., high, median, and low) can be employed to span the range of possible outcomes. Here, the robustness of alternative responses and the potential value of hedging strategies can be explored, but only if the scenarios capture a wide range of changes in key climate variables such as temperature, precipitation, and sea level rise. The diversity of possible futures is particularly critical to explore if the direction of change in a key variable such as precipitation is not clear (for example, in cases where climate models do not give consistent projections or predict whether precipitation increases or decreases). If adaptations are expensive, decision makers might want to judge the appropriate timing for incurring the costs of adaptation investments. In the context of coastal 

Managing the Climate Challenge flooding, for example, property owners might want to explore the frequency of other sources of similar vulnerability (e.g., extreme local precipitation events) to judge po- tential ancillary benefits of adaptation investments. For example, elevating houses in the face of rising water will not only reduce the potential losses to one’s own property but also alleviate damage to neighboring structures. Effects of climate change, includ- ing rises in sea level, increases in storm frequency, and changes in the ecological prop- erties of natural systems (such as loss of storm-buffering wetlands or mangroves), not only will impact coastal infrastructure but will also alter potential tradeoffs between different approaches to reducing risk (CCSP, 2009b). Perceiving Risk Risk perception is concerned with the psychological and emotional factors (e.g., anxi- ety, regret, and peace of mind) that have been shown to have an enormous impact on behavior and that need to be considered when developing risk-management strate- gies (Slovic, 2000). Decisions are affected by the perceptions of those who make them, so the potential importance of risk perception cannot be overestimated. There is a wide disparity between the views held by the general citizenry and those of experts about risks associated with climate change—both the nature and seriousness of the consequences and their associated probabilities (Leiserowitz, 2005). There is also a growing body of evidence showing that emotions play an important role in individu- al’s decision-making processes. Rather than basing one’s choices simply on the prob- ability and the consequences of different events, as normative models of decision making would suggest, individuals are also influenced by emotional factors such as fear, worry, and love (Finucane et al., 2000; Loewenstein et al., 2001). These concerns deserve serious consideration when developing adaptation strategies for addressing the future impacts of climate change. In addition, an important factor in motivating protective actions by individuals is their knowledge about what to do to reduce one’s vulnerability to a certain hazard (Paton, 2008). These factors should be anticipated in discussions about the appropriate decision-support approach and taken into account when developing and communicating risk and managing risk strategies. Educational programs may, in these cases, be prerequisites for galvanizing public support for expensive but important, forward-looking responses (ACC: Informing an Effective Re­ sponse to Climate Change; NRC, 2010a). 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E Communicating Risk Well-designed approaches to explaining risk encourage the effective participation and interaction of technical experts, stakeholders, and decision makers in managing risk decision processes and deliberations. Poorly designed communication can breed resentment and mistrust (NRC, 1996b), especially when communication techniques are perceived as biased or inappropriate to the audience. A growing number of stud- ies have shown that communication of risk and uncertainty is important in helping people respond to climate change (NRC, 1996b, 2010a). What most risk researchers consider the ideal approach for communicating uncertainty and risk focuses on es- tablishing an iterative dialogue between stakeholders and experts, where the experts can explain uncertainty and the ways it is likely to be misinterpreted; the stakeholders in turn can explain their decision-making criteria as well as their own local knowledge in the area of concern; and the various parties can work together to design a risk- management strategy, answering each others’ questions and concerns in an iterative fashion (Fischhoff, 1996; NRC, 1996b; Patt and Dessai, 2005). Designing and Implementing Risk-Management Strategies Based on case studies and its own experience, the panel suggests that providing a portfolio of options for managing risk is likely to be more effective than relying on a single solution. Using multiple strategies simultaneously—such as providing public education (i.e., communicating risk), offering economic incentives (e.g., subsidies, fines, or tax incentives), or intervening directly to prevent or avoid consequences (e.g., by implementing regulatory standards or restricting activity)—provides the most robust way to address risks. The multiple strategies chosen sometimes involve public-sector actions (e.g., regulations, standards); in other circumstances, they can include strate- gies to spread or transfer risk (e.g., offering or requiring insurance and/or compensat- ing for losses). Strategies for managing the risk can be evaluated in a variety of ways (see detailed discussion below). “Robust decision making” tests a number of different options and results in a decision path that keeps as many future options on the table as possible (ACC: Informing an Effective Response to Climate Change; NRC, 2010a). Currently, however, there is inadequate information about the effectiveness of adap- tation options in many specific applications, frequently because essential metrics for evaluation are unavailable or because the responsible party perceives the benefits from monitoring outcomes to be insufficient to justify this activity. For now, much can be learned through discussions, collaboration, and applying lessons learned from experiences at the local or state level or in other countries. Learning by doing, as well 

Managing the Climate Challenge as by deliberately testing different adaptation approaches (e.g., NRC, 2009a), sustained monitoring, collection, and analysis of the right data will be essential if we are to identify lessons and evaluate effectiveness. Furthermore, it is challenging to assess the net value of an adaptation measure given the uncertainties associated with changes in climate and impacts as well as the long time frames over which climate change will happen. Designing assessment programs to evaluate adaptation costs and successes critically is therefore essential. Research in this area should recognize that adaptations will likely need to be adjusted as the climate continues to change and that, in some cases, the actual benefits of adaptations may not be obvious or measurable for many decades following the investment. There is also a need for risk-management approaches that accommodate multiple metrics (standards of measurement) of climate impacts, and for decision-support tools that complement more traditional cost-benefit approaches of policy analysis (see, e.g., Yohe, 2009a,b). Many impacts (on ecosystems, for example) and many contexts (in- cluding social consequences) cannot be fully monetized (Downing and Watkiss, 2003). If decisions are made comparing only economic measures quantified exclusively in financial terms, then social and ecological consequences and other nonmonetized impacts cannot be considered in proportion to their significance. While it is essential to communicate the risks of inaction, it is equally essential that the risks of any potential adaptation action—including indirect consequences—be effec- tively communicated. For example, those residing in areas that are protected by dams or levees are likely to believe that they are fully protected against future flooding or storm surge. In reality, some levees have been poorly designed, as evidenced by Hur- ricane Katrina, but it is only after a hurricane or flood that attention is drawn to these inadequacies. Furthermore, there is likely to be new development in these regions unless officials and the public are made aware that it is possible for these flood-control and engineering solutions to fail. The result, known as the “levee effect,” can be losses that are much larger than they would have been if the risks had been correctly per- ceived and economic development in these areas had been limited in the first place ( Tobin and Montz, 1997). As noted above, perceptions of risk are often inconsistent with scientific approaches to assessing risk. Factors such as fear and anxiety impact judgments of risk, and short- sighted behavior is common, making it particularly important to design adaptation strategies that encourage individuals to take a longer-term perspective in their own best interest (and that of society more generally). Given the tendency of decision mak- ers to evaluate the net benefits of strategies over only a 2- to 3-year span, it may be necessary to provide short-term returns to encourage the adoption of long-term ad- 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E aptation strategies. For example, long-term contracts with short-term returns may be required to encourage investment in cost-effective adaptation measures for dealing with increasing damage from future floods or hurricanes as sea level rises (see Box 4.8, later in this chapter). In this case, long-term flood insurance (to spread risk) and long- term home improvement loans (to finance adaptation measures) might be combined with initial discounts on annual premiums that are likely to exceed the annual cost of the loan (Kunreuther and Michel-Kerjan, 2009). A complementary approach is to revise and enforce land use regulations and build- ing codes using standards that reflect the risks of climate change impacts. In the case of building codes, the challenge is to apply them to existing structures in harm’s way rather than just new structures. Often such retroactive codes are necessary, particu- larly when property owners are not inclined to invest in adaptation measures on their own—either because they perceive a disaster will not happen to them or they be- lieve the risk is small relative to the cost of adaptation. Insurance premium reductions coupled with long-term loans could make well-enforced building codes more palat- able to property owners. DEvELOPINg AN EFFECTIvE ADAPTATION STRATEgy Because the perception that climate fluctuates around a stationary mean is in conflict with recently observed climate dynamics (Milly et al., 2008), decision makers need an approach that is responsive to changes in the likelihood of extreme outcomes as well as changes in the “average” climate. Resources and natural processes may change their function and their location, and in some cases may cease to exist (IPCC, 2007a; West et al., 2009). Rather than managing the resource to maintain its past condition and state, management may need to take steps to protect the resource (e.g., building coastal defenses) or allow the resource to change as needed to adapt to climate change (e.g., allow migration of species to new habitats or manage forests for fire control instead of for timber). In other words, the managers of these resources must work to incorpo- rate the impact of climate change in their plans and operations. Instead of managing for resilience (which implies returning to the status quo), managing for change might become a more feasible approach (West et al., 2009). This chapter uses the recent example of New York City (see Box 4.1), one of the most comprehensive approaches so far to adaptation in the United States, to illustrate some basic principles for developing and implementing an effective adaptation strategy. There are a number of other examples of municipalities and states (large and small) that have developed and begun implementing adaptation strategies. Keene, New 0

Managing the Climate Challenge bOx 4.1 The New york Experience New York City responded to the challenges of a changing climate by creating several par- ticipatory mechanisms: broad public input through PlaNYC, a Climate Change Adaptation Task Force, and a Policy Working Group. PlaNYC was announced in December 2006 as a sustainability and growth management initiative to answer the question of what kind of city New York should be—posing the question “Will you still love New York in 2030?” After PlaNYC was announced, a top-to-bottom outreach effort began to receive input on goals for 2030. Staff met with thousands of community leaders and representatives and received thousands of e-mail suggestions. This input was synthesized into “10 goals for 2030,” which became the basis for PlaNYC. The plan’s scope was soon expanded to consider climate change as a major threat to sustain- ability.The 10 goals of PlaNYC are distributed across three challenges areas (growth, infrastructure, and the environment) and six planning elements that correspond to the city’s environment: land, water, transportation, energy, air, and climate change.1 Responding to strong leadership from the mayor’s office under Michael Bloomberg, New York City created a Climate Change Adaptation Task Force that included various private and public stakeholders. The stakeholders were divided into working groups that represent broad categories of infrastructure: communications, energy, transportation, water, and waste. In ad- dition, a Policy Working Group was convened to review the codes, rules, and regulations that govern infrastructure in New York City and to identify those that may need to be changed or created to help the city cope with climate change. Each working group provided a forum within which stakeholders could identify common vulnerabilities, share best practices, take advantage of potential synergies, and develop coordinated adaptation plans. At appropriate stages in the Task Force process, the individual working groups came together to ensure consistency, identify opportunities for coordination, investigate impacts of adaptation strategies on other sectors, and develop cross-sector adaptation strategies. Since the Policy Working Group’s focus on the regulatory context spanned a broad range of issues, it was particularly vigilant in coordinating its efforts with other working groups. Adaptation strategies that impacted multiple stakeholders were identified as possible citywide strategies and forwarded to the full Task Force for further evaluation and development. 1For details, consult http://www.nyc.gov/html/planyc2030/html/plan/plan.shtml. Hampshire (ICLEI, 2007), is, for example, a small municipality that is carrying out a simi- lar effort in a much different context. The panel focuses initially on New York, however, because the city has documented its steps very carefully, including peer review, in de- signing a plan that incorporates the impacts of climate change as a threat to sustain- 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E ability, and it has worked to create decision-support templates that may be useful for others. New York City’s Climate Change Adaptation Task Force used a common set of climate change projections that were developed with support from the Rockefeller Founda- tion by the New York Panel on Climate Change (NPCC) in the Climate Risk Informa- tion workbook (NPCC, 2009). The NPCC projections allowed stakeholders to gain an understanding from the outset of the climate science, initial potential impacts derived from existing and evolving climate variability, and uncertainties. This ensured that the inventories of infrastructure at risk and associated adaptation strategies were based on the same state-of-the-art climate change projections. Two key aspects of an adap- tation strategy—organization and objectives—are explored in the following sections. Organization of Adaptation Efforts Snover (2007) outlines steps that governments can follow to adapt to climate change, including establishing public engagement and planning processes. Developing an ad- aptation strategy can require involvement of many stakeholders (Smith et al., 2009b), as the New York City experience has shown. In government, all departments managing affected resources need to be involved in developing the strategy, including budget and legal departments. Stakeholders who will be affected by climate change or who will be involved in implementing adaptations should also have a role, and each group is likely to bring different values, objectives, and perspectives to the process. Since stakeholders are likely to have diverse objectives, clear leadership is needed from the outset in the development of adaptation strategies. Direct input and engage- ment of a chief executive of the government is typically required to make a clear and pressing case that adaptation is important. The development and implementation of the strategy can be directed from the chief executive’s office or coordinated by a lead agency. The advantage of managing it from the chief executive’s office is that it can demonstrate the chief executive’s commitment and avoid turf battles among depart- ments. On the other hand, running a coordinated effort out of a larger department might provide access to more staff and resources typically affiliated with a depart- ment compared to the chief executive’s office. Defining Objectives Defining objectives is a key part of developing any climate change adaptation strat- egy (Burton, 2008; King County, 2007; Snover, 2007; Theoharides et al., 2009). Objectives 

Managing the Climate Challenge can be tied to goals and used to define metrics for measuring success and monitoring progress. Clear goals facilitate setting criteria for monitoring the success of programs that are designed to meet new challenges over time (NRC, 2005b). If goals and priori- ties are broadly stated and not clearly defined, developing strategies to meet them will be more difficult. For example, goals such as “protect human health and welfare,” while laudable, may not give sufficient precision to develop specific metrics. Such a goal may conflict with another goal, “develop levels of protection that are not too costly.” Defining acceptable levels of risk for planning purposes—for example, risk of mortality of one in a million or risk of property damage from an extreme event of one in a hundred—can be justified in the context of precise and prespecified goals (NRC, 2005b). Decision makers often construct or select plans that are designed to achieve multiple goals. For example, a plan to invest in loss-reduction measures (e.g., elevating a struc- ture) to reduce the magnitude of damage from a future flood may have three goals: (1) reducing the magnitude of a catastrophic loss, (2) reducing anxiety about the pos- sibility of a severe loss, and (3) not incurring a large up-front cost for instituting the measure. The decision on whether to undertake an adaptive measure depends on the tradeoffs between values assigned to these sometimes-conflicting goals and the likeli- hood of achieving each goal (Krantz and Kunreuther, 2007). Ideally, the adaptation planning process begins by defining goals and objectives, then examining options to meet these goals in terms of their impacts on different stake- holders. A fundamental issue to address is whether preexisting strategic goals will continue to be appropriate or feasible in light of anticipated climate change impacts or whether these former priorities will need to be modified. This issue centers around whether adaptation will allow the goals to be met as before or whether goals need to be adjusted because climate change alters the feasibility of achieving them. For example, a preexisting goal of maintaining agricultural productivity in a region may still be achievable under climate change if farmers can modify management practices or use more inputs such as herbicides or water. In those cases, farming might still be profitable, but with reduced profit. In other circumstances, however, farmers in the re- gion may need to change crops to meet changing climate conditions, because climate change has reduced the productivity of old crops. In still other cases, farming in the region may not remain feasible in the long term, and the land might need to be retired from farming. Whether a preexisting goal can be maintained or needs to be modified will depend in each case on specific local circumstances. The relative importance of a previous goal may also change when climate change is considered. The discussion above suggests that an overriding goal may be one of accommodating 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E bOx 4.2 New york City’s Objectives New York City chose to define its objectives in terms of the “acceptable levels of risk” that are embodied in its current codes and regulations. While it is difficult to quantify society’s acceptable level of risk, it turned out to be relatively easy to identify certain things that New Yorkers would perceive as unacceptable, such as allowing the New York City subway system to flood multiple times per month. The city also recognized that society’s acceptable levels of risk could change over time as the climate changes. Indeed, if adjustments in acceptable risk levels were not made for climate changes, then associated changes in climate variability would likely result in more frequent episodes of intolerable consequence. It became clear, as a result, that accepting risk as a metrical implied that an adaptation process should create “flexible adaptation pathways” that would allow policy makers, stakeholders, and experts to develop and implement strategies that evolve as climate change progresses. Moreover, it became clear that flexible adaptation pathways can only be constructed on the basis of solid understandings of current and future climate hazards, rigorous evaluations of regulations and design standards, and interactive decision-support tools that help infrastructure managers to plan adaptation strategies. Monitoring and reassessment of climate science, adaptation strategies, and policies are critical as well, so that responses to the evolving risks of climate change can be adjusted effectively (NPCC, 2009). change (see Box 4.2), either directly, by implementing adaptation options, or indirectly, by changing management goals and expectations if climate change makes them no longer achievable (West et al., 2009). DEvELOPINg AN ADAPTATION PLAN Like other planning processes, adaptation planning includes identifying potential problems, developing options to address them, ranking them according to criteria, and selecting the ones to be implemented. Climate change adaptation should, if pos- sible, be incorporated into established planning activities, or “mainstreamed,” as New York City has done, rather than requiring a separate approach. There may be common solutions to some problems, but no one approach will be appropriate for all applica- tions. Whereas Chapter 3 discusses adaptation options in depth, this section briefly discusses approaches for identifying and selecting options. Given the realities of ongoing changes in climate and uncertainty about the effective- ness of currently available adaptation options, the most important principles behind effective adaptation planning are flexibility and an adaptive approach designed to 

Managing the Climate Challenge 3. Develop an adaptation strategy using risk-based prioritization schemes 2. Assess the 4. Identify opportunities vulnerabilities and for co-benefits and risk to the system synergies across sectors 1. Identify current and 6. Monitor and 5. Implement future climate changes reevaluate implemented adaptation options relevant to the system adaptation options FIguRE 4.1 The planning process is envisioned to incorporate the following steps: (1) identify current and future climate changes relevant to the system, (2) assess the vulnerabilities and risk to the system, (3) develop an adaptation strategy using risk-based prioritization schemes, (4) identify opportunities for co- benefits and synergies across sectors, (5) implement adaptation options, and (6) monitor and reevaluate implemented adaptation options. meet objectives and goals under a wide variety of future climate conditions (Glantz, 1988; Smith, 1997). To build flexibility and an adaptive approach into the planning process, monitoring and reevaluating the implementation is a key element (Figure 4.1). Since future emissions of GHGs, climate sensitivity (i.e., how much average global temperatures will increase with a given concentration of GHG), and regional pat- terns of changes in climate are not certain, we cannot develop adaptations now for a specific future climate. Groves and Lempert (2007) used the term “deep uncertainty” to describe the wide range of climate conditions planners and others must cope with. Therefore, monitoring of the climate changes, vulnerabilities, and impacts is also nec- essary and subsequently requires decision makers to reevaluate and update the plan- ning process (Figure 4.1). The adaptations need to meet goals and objectives across this wide range of climate conditions. Identifying Adaptation Options Hence the principle of flexibility: adaptations must perform well under a variety of future climate conditions. This means that adaptive responses must either be able to change to keep pace with different climate conditions or be able to absorb a wide range of climate conditions. Changing in response to changing climate conditions 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E may involve being responsive to climate and other signals. For example, market mech- anisms such as prices can be responsive to changing conditions. Using water markets to set water rates can allow for rates to rise when water supplies are tight (e.g., during droughts) and fall when supplies are abundant (e.g., during wet periods). Such adapta- tion mechanisms can be described as being resilient. A key issue for climate change adaptation is the capacity of the affected system to recognize and quickly respond to signals of changes in climate. (Note the approach need not be cognizant of changes in climate, just changes in conditions. The price of water might rise as supplies tighten, regardless of peoples’ perceptions about climate or the causes of a current drought.) The second case—designing adaptations that can absorb a wide range of climate conditions—means the affected system must be able to continue functioning as intended even in extremes. This case may best apply to design of infrastructure such as water supply, treatment, flood protection, and roads. Such infrastructures are typi- cally designed to be robust—to withstand extreme events and continue to provide intended services. Climate adaptations can fall into either of two categories: “no regrets” or “climate justi- fied.” No-regrets strategies are ones that can be justified without taking into account climate change but which also meet goals and objectives of adaptation to climate change. Examples of no-regrets adaptations include reforming insurance regulations to enable insurers to set rates that reflect risks. (Despite the label, “no-regrets” policies can entail winners and losers: they do not mean that all stakeholders are better off or satisfied.) Climate-justified adaptations, on the other hand, are those that are under- taken mainly because climate is changing or anticipated to change. For example, this might involve raising a flood barrier in anticipation of future increases in sea level or storm intensity (Reeder et al., 2009). Each of these approaches may be both complex and difficult to implement. For ex- ample, no-regrets strategies may perform well with modest changes in climate but may be inadequate for extreme changes. In the case of market mechanisms, the price of water could become unaffordable for low-income households in extreme droughts if set by the market; also, market mechanisms rarely protect environmental interests. Hence, the public sector might have to intervene in some way to ensure equity and provide assistance to those groups harmed by such adaptations. Box 4.3 describes the process New York City used to identify adaptation options. 

Managing the Climate Challenge bOx 4.3 Identifying Adaptation Options in New york New York City employed three tools as it worked to identify and analyze adaptation options through the Climate Change Adaptation Task Force: 1. Infrastructure questionnaires. Sector-specific questionnaires were designed to help stakeholders create inventories of their infrastructure at risk to climate change impacts, especially those impacts driven by dynamic climate variability. 2. Risk matrix. A tool was designed to help stakeholders categorize their lists of at-risk infrastructure based on likelihood of impact and magnitude of consequence. 3. Strategy framework. A framing tool was designed to assist stakeholders in developing and prioritizing adaptation strategies based on criteria related to factors such as effec- tiveness, cost, timing, feasibility, and co-benefits. Together, these process-based tools provided the foundation for the development of climate change adaptation plans for critical infrastructure in the New York City region. The location of these adaptation plans within an overall planning process is described in detail in the Adapta- tion Assessment Guidebook created by the NPCC (2010). Perhaps more importantly and similar to Figure 4.1, the process includes monitoring and assessment of results, which feeds directly into subsequent iterations of the same process. It is therefore envisioned as a dynamic cycle of analysis and action followed by reanalysis and possible adjustments to or continuation of previous actions (learn, then act, then learn some more). The New York approach therefore embraces completely the need for flexible adaptation pathways that evolve over time as understanding of the climate as well as the local, national, and global economies change. Indeed, as of the summer of 2009, the Bloomberg administration intended to push the City Council to pass a law that would require each subsequent administration to submit progress reports and revised climate adaptation plans, just as each is now required to submit updates on progress toward sustainability goals. Comparing and Selecting Adaptation Options As the previous chapters indicate, many potential adaptation options can be identi- fied. There may be multiple options for the same decision or more options than can be afforded. Thus, options must be prioritized and selected before implementation can begin. This section suggests some criteria that can be used to set priorities and selec- tion criteria for adaptation options and describes methods that can be used to aid decision making. 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E Considering benefits of Adaptation An important factor in setting priorities will be the relative effectiveness of adapta- tions in reducing adverse impacts (or taking advantage of positive impacts) of climate change. Managed systems such as water resources or agriculture may be more amena- ble to successful intervention than systems that are subject to relatively little manage- ment such as natural ecosystems. While it may be feasible to compare the effectiveness of various adaptation options within a sector using accepted metrics for that sector, comparing adaptations across different sectors creates methodological issues. To set priorities across sectors, the choice of metrics becomes more complicated because different metrics may be ap- propriate for different sectors. Co-benefits An additional consideration is whether adaptations have co-benefits. That is, does an adaptation create benefits beyond the immediate goals and objectives of adapting a specific system to climate change? For example, protecting coastal wetlands is an adaptation option that may reduce vulnerability to coastal storms. Such wetlands can also provide breeding grounds for fish as well as recreation and tourism amenities, expanding the total benefits of a project. Co-benefits such as these add to the direct benefits of adaptation, raising the relative value of an adaptation option. In fact, many adaptation options listed in the previous chapter currently offer more benefits from adaption to other stressors than to climate change, although it is anticipated that such options also increase resilience to changing climate conditions. Adverse Impacts Often overlooked in discussions of adaptation are the potential adverse consequences of adaptation strategies themselves, particularly when they involve engineering solu- tions. For example, the use of coastal barriers to protect structures or property from erosion as sea level rises blocks natural migration of wetlands and results in loss of beaches (CCSP, 2009b). Similarly, building reservoirs to capture stream flow can alter natural flow patterns and block migration of fish and other aquatic species. Reser- voirs also reduce sediment delivery to delta systems, exacerbating beach erosion and impacts from sea level rise (CCSP, 2008a). Often, adaptations in one sector can create adverse impacts in another system or sector. Impacts across multiple sectors can com- 

Managing the Climate Challenge plicate the task of quantifying the adverse impacts in a single or common metric that can be compared with benefits. Adaptation Costs Cost is also a factor in setting adaptation priorities. Everything else being equal, the greater the adaptation costs, the less attractive an adaptation option will be. All the costs of implementing adaptations, including capital costs, maintenance and opera- tions over time, reconstruction, and staffing, should be counted. Limitations on avail- ability of staff or availability of staff with the necessary training, experience, or other credentials to implement adaptations may also add to the cost. Timing of Impacts The timing of climate change impacts can be a factor used to set priorities in planning for and implementing adaptation (although the uncertainties about the rate and mag- nitude of climate change discussed in Chapter 2 will also affect projections about the timing of impacts). The following issues influence considerations about timing: • When will climate change impacts become critical? • Have impacts already become critical? • Does the observed impact appear to be clearly linked to climate change or could it be the result of natural variability? • How much time will be needed to react to, prepare for, or develop adaptation infrastructure to cope with the anticipated impacts? The question of needed reaction or preparation time is particularly important. If it is possible to quickly react to projected impacts as they happen, then having longer- term adaptation strategies may not be critical. But, if impacts need to be anticipated, then projections of future conditions will be needed, particularly for decisions about large infrastructure projects that can require decades to plan, finance, and build. Long lead times will likely mean preparing for more uncertainty and a wider range of future conditions (see Box 4.4). As climate continues to change, more and more impacts will become evident, and detection and attribution of impacts will become more important (e.g., DOI, 2008a). Detection is the first step in addressing impacts as they happen, and this will require development of monitoring systems that have sufficient regional coverage and fre- 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E bOx 4.4 uncertainty and Adaptation Choices: An Example from the gulf Coast A recent report by the U.S. Climate Change Science Program, Synthesis and Assessment Product 4.7, Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study (CCSP, 2008a), considered vulnerabilities of this region to a combination of sea level rise, more intense storm activity, and land subsidence. According to this report, the region is likely to see apparent sea level rise (actual sea level rise plus land subsidence) of 2 to 4 feet by 2050. Combined with prospects for more severe storms over the decades, this would put significant settlements, infrastructures, and environments at serious risk. Adaptation options for vulnerable coastal areas are well known (Chapter 3). The main categories are protecting coastal systems with barriers, such as the Netherlands’ dikes; hardening coastal systems so that they can handle higher water levels and storm impacts; sharing risks to particular places from low-probability/high-consequence events through insurance; and changing land uses in the region to move vulnerable activities and systems away from vulnerable areas. Some decisions about adaptation approaches seem relatively clear. For example, existing coastal energy and chemical facilities are likely to be diked in order to protect them against another possible Hurricane Katrina in coming years; and coastal cities are being strongly encouraged to improve their emergency preparedness systems. But deciding what to do in the next several years is shrouded in uncertainties. At what rate will the threats develop? Will the apparent sea level rise be 2 feet or 4? How strong does “more intense” mean? What would be the costs of the various options, and who would bear them? What is likely to be the response of the federal government to a regional challenge that is of national importance? quency of measurement. Just as important is the ability to analyze the information to detect impacts that may be the result of climate change. Methods for Comparing and Ranking Adaptations Formal methods available to compare and rank adaptation options include cost-ef- fectiveness analysis, benefit-cost analysis, risk analysis, and multicriteria analysis. These methods differ in terms of information they require and information they provide to decision makers. This section briefly reviews these methods, while acknowledging that none of them are especially good at incorporating social or environmental costs or benefits. 0

Managing the Climate Challenge What will be the perspectives of private insurers? What should parties considering new infrastructure investments do? This is a classic case of a very high-probability threat, whose magnitude and time frame are pro- jected with a high level of confidence, that will challenge America’s ability to make decisions under uncertainty. It is deeply imbedded in decisions by the private sector—from energy firms to real estate firms and the insurance industry—and state and local governments. It involves politically charged near-term decisions to protect current settlements, infrastructures, and environments that may not be the right decisions for the longer term. Addressing these uncertainties in such a complex context involves weighing urgency of action (which in the near term is focused on protection from more intense coastal storms) against resources needed for adaptation. In the near term, coastal infrastructures can be protected by barriers and/or by hardening (e.g., raising roadbeds). In the longer term, however, risk-averse investment strategies are likely to encourage some movement away from some especially vulnerable areas, while hard deci- sions are made about iconic systems and structures to protect, even at a high cost. In preparation for longer-term participatory strategy discussions, information systems need to provide a steady stream of information about the rate of change in climate change and land subsidence parameters, the rate of voluntary change in land uses in vulnerable areas, and emerging evidence about impacts. And mechanisms need to be developed and used for continuing reevaluation of risks as some uncertain- ties are reduced. Making adaptation decisions under uncertainty is in fact an evolutionary process, beginning with relatively low-cost actions that make sense under a range of future conditions, informed by recent experience. It continues with effective information systems to inform further decisions, and it emerges adaptively with a broad-based participatory process reconsidering risk-management strategies as some uncertainties are reduced. Cost-Effectiveness Analysis Cost-effectiveness analysis is used to compare alternatives that are expected to achieve the same or a similar goal or benefit. Alternatives are compared based on their relative costs, that is, which alternative costs the least to achieve (approximately) the same goal or outcome. This approach is often applied to examine options for reducing GHG emissions to achieve a certain level of atmospheric GHG concentra- tion. Indeed, this was the point of the “when efficiency” of the Wigley et al. (1996) emissions scenarios—to show that the same concentration limits could be achieved while minimizing the discounted cost of the mitigation interventions over time. Using cost-effectiveness analysis to evaluate adaptation alternatives is appropriate if the objectives or benefits of adaptations are clear and consistent. In many cases, however, there can be multiple benefits of different adaptation measures, making it difficult to 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E make comparisons across alternatives. Alternatives may also have different benefits and can involve a wide range of diverse adverse impacts on other systems (e.g., hard coastal defense structures resulting in loss of beaches or blocking inland migration of wetlands). In such cases, use of cost-effectiveness as a metric for evaluating adaptation alternatives may be inappropriate. benefit-Cost Analysis Benefit-cost analysis (BCA) is a systematic procedure for evaluating alternatives that have an impact on society. BCA attempts to determine which alternatives have the greatest net benefits (difference between benefits and costs) or have higher benefit/ cost (B/C) ratio (the ratio of benefits to costs; e.g., Boardman et al., 2001; Loomis, 1993). Each of the alternatives will affect a number of individuals, groups, and organizations in our society. For each alternative, one needs to specify the resulting benefits and costs that impact each of the interested parties. If there is uncertainty associated with the analysis, then one has to assign probabilities to the different states of nature (e.g., floods or hurricanes of different magnitudes) and the resulting outcomes of the inter- ested parties. If the alternative involves multiple time periods, then one has to specify the outcomes that occur in each of these future periods and use a social discount rate to convert these benefits and costs to present value. Once these benefits and costs have been specified, then one needs to quantify these impacts and attach some dollar value to them for each of the affected individuals. BCA uses a common metric—typi- cally money—to compare all benefits and costs in order to determine if benefits exceed costs. The use of monetary metrics has led to criticism that this method fails to capture nonmonetary values such as protection of ecosystems or human life (Brau- man et al., 2007). A further disadvantage of the use of money as the common metric is that gains or losses to those societies or individuals with the most wealth can effec- tively count more than impacts to those with less wealth. This can be addressed by weighting losses to the poor more than the rich (Azar, 1999). Incongruous timing of when benefits and costs are realized also presents challenges for application of BCA. When costs and benefits are distributed into the future, dis- counting expresses them all in terms of current dollars. Benefits far into the future or subject to high discount rates will be relatively small in present value terms. BCA can be particularly limited in analyzing benefits and costs over many generations, as may be the case when analyzing the impact of climate change adaptations. Adaptation measures for reducing the consequences of climate change normally involve an up-front investment cost that provides benefits over a number of years. The 

Managing the Climate Challenge nature of these benefits will be a function of the impact that climate change is likely to have on the environment. For example, if global warming produces increasing sea level rise during the next 50 years, then adaptation measures making structures less vulnerable to damage from flooding will have higher discounted expected benefits over the life of the structure than if there was no increase in sea level rise due to global warming. Due to the uncertainty associated with the nature of climate change over the next 30 to 100 years, it is important to undertake sensitivity analyses to see how robust specific adaptation measures are to different scenarios regarding the nature of climate change. If the net expected benefits or the B/C ratios are positive over a wide range of plausible scenarios, then these adaptation measures would be viewed as desirable. Risk Management A risk-management approach to confronting climate change (Carter et al., 2007; Schneider et al., 2007) is gaining traction as a complementary analytic tool because it is designed explicitly to make up for many (but by no means all) of the thorny issues as- sociated with BCA. Risk-based analyses rely heavily on information about the relative likelihoods of possible events, which can be challenging to determine in the case of climate change impacts for reasons discussed earlier. Others, including the ones that relate to identifying robust strategies, can be built directly from catalogues of pos- sible futures, even if they cannot be characterized in terms of their relative likelihoods ( Yohe, 2009b). Here too, the selection of a metric or metrics can enable or limit com- parison of risks across sectors and impacts. Although there are techniques for doing so, the panel has already noted that as- signing probabilities to different climate change outcomes can be challenging. One approach used by some decision makers is not to assign probabilities to different scenarios. In such cases, decision makers may treat different scenarios as equally likely or may focus on the “worst-case” scenarios and ensure that they are prepared for such outcomes. Risk analysis also incorporates risk perception of individuals, which is normally not considered in undertaking BCA. If decision makers underestimate the value of specific adaptation measures by focusing on their benefits only over the next several years rather than the relevant time horizon (e.g., the projected life of the property where an adaptation measure is considered), then they will underestimate the net benefits of the measure of the B/C ratio. Similarly, if the likelihood of specific events is underes- timated relative to the scientific data, then the adaptation measure will be perceived 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E to be less effective than it otherwise would be. There is thus a need to develop risk- management strategies and incentives to encourage the investment in adaptation measures that are viewed as attractive from a benefit-cost approach. (See Box 4.8 for a discussion of innovative risk-management approaches for the National Flood Insur- ance Program.) Box 4.5 is devoted to a discussion of the challenges involved in characterizing un- certainty with sufficient clarity that risk-analysis and risk-profiling techniques can be applied in ways that enable one to evaluate the relative attractiveness of different adaptation measures. Combining consequence and likelihood can provide estimates of the expected values of outcomes. It is often more informative to determine the relative importance of con- sequences or likelihood in producing high-risk vulnerabilities that should receive the most attention. Box 4.6 describes how New York City considers risk from a very practi- cal perspective that recognizes both its formal definition and the constraints imposed on its application by limited information. Decision Analysis (Statistical Decision Theory) Decision analysis (DA) has a structure similar to BCA with two major differences. It normally focuses on a decision made by a specific interested party (e.g., a homeowner, an industrial firm, or a division in an organization) rather than viewing the alternatives from the perspective of society as BCA does. It also explicitly considers the impact of uncertainty on the choice between alternatives through the construction of a decision tree, in which different branches reflect the likelihood of specific events occurring and their consequences as a function of the alternative being considered. It is thus rela- tively easy to examine the value of new information regarding climate change scenar- ios on the choice between alternatives. If one is interested in the ways that different interested parties will be affected by specific adaptation measures, then DA would be an appropriate approach to use. As with BCA, DA can be complemented by risk man- agement as discussed above, but it is equally dependent on credible characterizations of the relative likelihoods of alternative futures. 

Managing the Climate Challenge Multicriteria Analysis BCA and DA normally focus on a single metric by converting all impacts into monetary values. In many cases it may be appropriate to introduce multiple attributes into the analysis and examine the tradeoffs between them. For example, if there are environ- mental impacts that are difficult to convert into a monetary value or one wants to focus on the number of lives impacted by a particular alternative, then multicriteria analysis may be a more appropriate way to structure the problem. One way to com- bine these attributes would be to use a common metric such as utility and determine the weights that different attributes have in determining the aggregate utility of one alternative over another (see Keeney and Raiffa [1976] for techniques for doing this). Multicriteria analysis (MCA) could thus be used as a complement to BCA or DA in evaluating the relative attractiveness of different adaptation measures with respect to decisions at a societal level (BCA) or by specific interested parties (DA) (see Depart- ment of Communities and Local Government [2009] for an example of the use of MCA in the context of adaptation to climate change). Risk profiles borne of risk analysis and calibrated in whatever metric is most appropriate can also be employed to convert disparate vulnerabilities into comparable format (see, for example, Yohe, 2009b). In such cases, it is the political process that converts this information into relative rank- ings of significance for decision makers facing constrained resources (i.e., the political process then conducts its own MCA de facto). Implementing Adaptation Plans In order to move from planning to implementation, the following issues need to be addressed: prioritization of actions, establishment of time lines, availability of finan- cial resources, and staffing needs. It is also important to establish a system to monitor the effectiveness of adaptations in achieving planning goals and to allow for adjust- ments to be made. Where appropriate, adaptation options that are not achieving their desired objectives should be adjusted, modified, or ended. In the latter case, it may be necessary to rethink how adaptations should be done. Box 4.7 summarizes how New York City addresses implementation in ways that recognize issues of timing (urgency) and expense. IMPEDIMENTS TO IMPLEMENTINg ADAPTATION PLANS AND POLICIES The panel’s evaluation of case studies has identified multiple barriers to effective implementation of adaptation programs and policies in the United States. Strategies 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E bOx 4.5 Characterizing uncertainty in the Climate System There are three main sources of uncertainty concerning future climate: the natural internal vari- ability of the climate system, the trajectories of future emissions of GHGs and aerosols, and the response of the global climate system to any given set of future emissions (Meehl et al., 2007). Internal variability refers to natural fluctuations of the climate system that occur in the absence of external radiative forcing due to, for example, increased concentrations in GHGs, aerosols from volcanic eruptions, or land use change. It is a result of the internal dynamics of the coupled atmosphere-ocean system. This internal variability includes natural fluctuations in large-scale phenomena such as the El Niño-Southern Oscillation. Uncertainties regarding future emissions and concentrations of GHGs and aerosols are derived from imprecise understanding of exactly how the world will develop socially, politically, economically, and technologically. Uncertainties regarding future emissions of GHGs are often viewed as qualitatively different from the uncertainties associated with the physical climate system, and there is considerably greater controversy associated with quantifying uncertainties of emissions pathways since they involve quantifying uncertainties in very complex interactions of future world societies (CCSP, 2009c; Parson et al., 2007). It is generally viewed as unlikely that uncertainties of long-range emissions (e.g., more than a few years) can substantially be reduced (CCSP, 2009c). Uncertainties about the response of the climate system to GHG emissions are normally analyzed using global climate models (GCMs). Different GCMs respond differently to the same radiative forc- ing and produce different patterns of climate change. These models provide information at relatively coarse spatial resolutions (hundreds of kilometers). The application of downscaling methods, such as regional climate models and statistical downscaling, yields higher-resolution projections but presents another source of uncertainty: the uncertainty associated with the spatial scale of the simulations. This last uncertainty can be particularly important in the context of adaptation planning, since adaptation studies or plans may require higher-resolution information about climate change. Uncertainties that cannot be readily quantified through use of even the full suite of GCMs available throughout the world (see IPCC, 2007b) still must be recognized. These include such uncertainties as processes that are missing from the climate models (e.g., for some, a fully coupled carbon cycle, and evolution of land use or cover change), processes that are not explicitly resolved (e.g., deep convec- tion) at typical global model spatial resolutions, processes that are not understood well enough to model successfully (e.g., certain aspects of ice sheet dynamics), and unknown processes. All of these uncertainties concern mainly the physical climate system. For further details on these physical system uncertainties, please see ACC: Advancing the Science of Climate Change (NRC, 2010b). The three main uncertainties vary in their relative importance based on the prediction lead time of interest. For nearer time scales of one or two decades, internal variability dominates, whereas at longer time scales, model uncertainty and emissions scenario uncertainty dominate (Hawking and Sutton, 

Managing the Climate Challenge 2009). The uncertainty in future human GHG emissions is the dominant contributor to uncertainty by the end of the 21st century. Considerable effort has gone into developing means of quantifying the known uncertainties regarding future climate change on various temporal and spatial scales. These have included simple ranges of results from climate models (e.g., the range 2.7–8.1°F [1.5–4.5°C] for global temperature change response to doubling of carbon dioxide [CO2]; Trenberth et al., 1995) qualitative statements of likelihoods (e.g., likely, very likely; Moss and Schneider, 2000), and probabilistic approaches (e.g.,Webster et al., 2003; Wigley and Raper, 2001). The most widely used language of uncertainty is probability, and generation of probability distributions for various variables related to future climate has taken off in the past 10 years or so (CCSP, 2009c), for example, probabilities of climate sensitivity (e.g., Andronova and Schlesinger, 2001), probabilities of regional climate change conditioned on specific emissions scenarios (Tebaldi and Knutti, 2007), probabilities of emissions scenarios (Webster et al., 2003; Wigley and Raper, 2001), and probabilities of elements in society that contribute to emissions pathways such as future population (O’Neill, 2005). Quantifying uncertainties in the physical climate system has relied primarily on two different types of climate model experiments: multimodel ensembles (MMEs), also known as ensembles of op- portunity, which are made up of the results of different global climate models subjected to the same radiative forcing; and perturbed physics ensembles (PPEs), wherein key but uncertain parameters of a single global model are varied to essentially create a large number of different model versions (e.g., Murphy et al., 2004; Stainforth et al., 2005). Most recently, particular effort has been expended to quantify uncertainties of future climate on regional scales using probabilistic methods—sources of uncertainty that are perhaps more relevant to adaptation planning. These were particularly emphasized in the last report of the Intergovernmental Panel on Climate Change (IPCC) (Christensen et al., 2007). Most recently, the United Kingdom Climate Projections (UKCP09) has used a combination of PPEs, MMEs, and regional climate model results to develop probabilities of changes in temperature and precipitation at a 25-km resolution (Murphy et al., 2009) for all of Great Britain. It is expected that this information will be used to determine probabilities of different impacts of climate change and possible adaptations. It must be remembered, however, that not all uncertainties can be easily quantified using straight- forward probabilistic methods. Subjective probabilities have been recommended for establishing probabilities of different emissions pathways (Fisher et al., 2007), for example. The deep uncertainties that result from unknown or incompletely known processes may not be amenable to probabilistic quantification (Lempert et al., 2004). Probabilities calculated for future regional climate change have in turn been used in impacts models (e.g., crop models and water resource models) to provide estimates of probabilities of impacts. This step can be viewed as part of a risk-assessment framework wherein the probabilities of the im- pacts form part of the input for risk assessment. One particular probabilistic approach that is directly relevant to adaptation planning is establishing probabilities of exceeding thresholds, for example, for some level of impact that may be beyond the coping range of a particular impact sector (Carter et al., 2007; Jones and Mearns, 2005). 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E bOx 4.6 The New york City Risk Matrix In evaluating risk, New York City stakeholders filled in an automated template that measures risk as a factor of likelihood of impact, if a given climate hazard event should occur, and the mag- nitude of the consequence of such an impact. Depending on the response for each category, the spreadsheet then automatically generated a placement on a two-dimensional risk matrix (see figure below). If the automatically generated risk did not align with expert judgment, the spreadsheet provided the opportunity for override with notes explaining the override decision. If an adaptation measure was under way or planned and fully funded, stakeholders were instructed to take into account the benefits gained from those measures when conducting this exercise. Instances were also considered where updated measures not explicitly related to climate change adaptation were already under way within an organization or agency that would provide ancillary benefits for climate change adaptation. The NYC risk matrix. A two-dimensional risk matrix was used to highlight the fundamental nature of the risk faced by specific types of infrastructure. SOURCE: City of New York (NPCC 2010). 

Managing the Climate Challenge bOx 4.7 Casting Adaptation to Climate Change Within New york’s Development Plans The implementation step (number 7 in Figure 4.1) cannot be done in isolation. Investments in adaptation programs must be integrated into budget decisions that recognize a myriad of competing demands for scarce resources. In its planning process, New York City has concluded that it is essential that both the urgency and the cost of any proposed adaptation response be compared with other adaptation options so that its place in the long-term sustainability plan- ning of the city can be determined and supported. The city developed a prioritization matrix to assist in this final step (see figure below). Notice, though, that the monitoring function in step 8 of Figure 4.1 must include not only adaptations that are implemented but also adaptations that are deferred. In that way, the flexible, iterative program can adjust its evaluation of urgency for the next round of decisions. In summary, climate change planning was embraced in New York City as a way to integrate ongoing plans focused on growth management, infrastructure, and environmental sustainability. Climate change was chosen as the integrating element because adaptation to changes in climate- related risks could serve as a focal point. This “mainstreaming” of climate change planning into other ongoing initiatives moved adaptation to an advanced stage very quickly. The public-private initiative that was developed, with vigorous and effective leadership from the Mayor’s Office, provided a coordinated approach while still allowing each stakeholder group to identify vulner- abilities and suggest pathways to resilience and sustainability. Prioritizing with respect to urgency and cost. Locating adaptation strategies that emerged from the evaluation process in a matrix that contrasts urgency with cost is the final step before an overall strategy for responding to climate change is brought into general budgeting and invest- ment conversations. SOURCE: City of New York (NPCC 2010). 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E exist for overcoming each of these barriers, although some are more easily overcome than others: Inadequate Information and Experience • There is a high degree of uncertainty about future climate impacts at a scale necessary for most decision making, and there are uncertainties associated with the complexity of interactions between natural and socioeconomic sys- tems. Because of these uncertainties, a variety of new management tools and region- and sector-specific data on likely climate impacts are needed, as well as new approaches to decision support. • There is limited knowledge and experience with adaptation in the context of climate change among decision makers, resulting in a need for “learning by doing” and deliberately testing new approaches. The prospect of a nonsta- tionary future climate system results in a need to design policies, monitoring activities, and processes that accommodate adaptive management. • Limited stakeholder awareness of climate-related risks suggests that better information, public education, and decision support are required. Inadequate Institutional Support for Adaptation • Conflicting mandates within federal agencies and incentives for maladaptive behavior within governmental programs suggest a need to change regula- tions and incentives that currently increase climate-related risk. • Lack of coordination across levels of government and between government and the private sector at multiple spatial scales means that mechanisms for interagency coordination need to be improved and networks of existing adap- tation capacity will need to be strengthened. • Inadequate institutional support for planning and implementing adapta- tions to climate change suggests that government and private-sector institu- tions need to be designed to (1) develop, interpret, and disseminate scientific information on climate change; (2) develop adaptation options; (3) help find resources to support adaptation programs; (4) enable adaptation projects to be implemented; and (5) monitor the success or failure of adaptations and enable corrective action to be taken. As with infrastructure-based solutions, however, institutions can either help or impede adaptations. Some institutions developed to support activities appropriate under prior climate conditions may discourage change and thus can impede adaptations. 0

Managing the Climate Challenge Lack of Resources and Technology for Adaptation • Many adaptation options will require financial investment, and insufficient capital or access to capital may limit options in many sectors or regions. If costs are too high, lower-cost options may be preferred or it may be possible to phase in adaptations to spread costs out over time. Inadequate resources can be addressed by (1) having a long-term investment strategy that includes identifying consistent sources of funding that are not subject to the vaga- ries of politics and (2) finding ways to limit the costs of adaptation, such as by mainstreaming adaptation into a wide range of decisions with climate- sensitive consequences, including reauthorization of laws affecting land and water use and construction or renovation of major infrastructure. • New technologies may be needed to adapt to climate change. There are many types of technologies that can help adapt, including agricultural cultivars that are resistant to heat, drought, or excess moisture; water conservation tech- nologies; and monitoring technologies. Research and development needs are further discussed in Chapter 7. • The role of infrastructure in protecting existing ecosystems and valued invest- ments needs to be considered. For example, having sufficient coastal protec- tion or water storage infrastructure can help societies adapt to changing sea levels or diminishing water supplies. behavioral Impediments • Behavioral impediments, such as a failure to acknowledge risks of climate change impacts, can be partially overcome through leadership, education, and better facilitation of decision processes. The likelihood that impacts will exceed the capacity to adapt in some regions and sectors creates a need to act quickly to reduce GHG emissions and to be better prepared for disasters. • A short-term perspective among policy makers, which limits the capacity to address problems such as sea level rise, needs to be replaced by consideration of both short- and long-term benefits as well as multigenerational equity. There is a tendency to discount the future at a much higher rate than would be used in benefit-cost analyses (Loewenstein and Prelec, 1992). Furthermore, decision makers tend to ignore risks when perceived likelihoods fall below some threshold of concern (Huber et al., 1997). • Underlying social and economic stresses that increase vulnerabilities to climate change impacts can be addressed by deliberately identifying and managing multiple stresses in an integrated manner. A sustainability-focused 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E solution set can be designed to solve multiple problems. Uneven access to adaptations among different income classes and populations can increase the vulnerability of society as a whole to climate change. The effect of inequity in vulnerability among such groups was clearly demonstrated in the immediate aftermath of Hurricane Katrina (Wilbanks and Sathaye, 2007). It should be noted that in general, such barriers are far more prevalent in developing countries than in the United States (Smit et al., 2001). Therefore, the vulnerability of developing countries to climate change is generally considered to be much greater. This topic is considered separately in Chapter 7 (see also IPCC, 2007a). LIMITS TO ADAPTATION Potential adaptations to climate change have physical, economic, and institutional lim- its. For example, there are practical limits to how high seawalls and levees can be built, how much irrigation water can be applied, and how large storm sewers and culvert capacities can be. Institutional practice (custom, regulatory, legal) further constrains adaptations. Typically, major capital investments are financed over at most a few de- cades, whereas the infrastructure can last a century or more. A change in infrastructure design that will mostly provide benefits beyond the finance period may be difficult to justify (AWWA, 2009b). Furthermore, some adaptation options have maladap- tive or unanticipated effects. A common example is the so-called levee effect, where establishing levees or seawalls encourages further development, thereby increasing catastrophic losses when the levees are eventually overtopped or seawalls breached ( Tobin and Montz, 1997). A framework for considering thresholds for major “reasons for concern” was introduced in Chapter 2. A thorough adaptation plan examines these limits to adaptation, even if probabilities of such outcomes are low (high-impact/low-probability events). As a result of con- sidering such outcomes, the planning process might include evaluations of whether objectives may need to be significantly changed. This can be a politically challenging topic to address because it involves admitting that adaptation strategies may not or cannot meet the objectives under all conditions. Contingency plans for such out- comes should be developed, although much research is needed on how to develop such plans. 

Managing the Climate Challenge RESEARCH AND DEvELOPMENT IN SuPPORT OF ADAPTATION While there are myriad adaptation options available to address vulnerabilities to cur- rent climate variability and extremes, research is urgently needed to devise innovative adaptation strategies to address the impacts of a changing climate. These strategies will need to tackle issues such as the unprecedented pace of change, the potential for crossing thresholds, the interaction of climate change with multiple other stressors, and the difficulties of anticipating the magnitude of extreme events. There is a major role for institutional innovation in adaptation. Box 4.8 suggests ways that the National Flood Insurance Program could be modified to reflect the risks associated with climate change while at the same time encouraging adaptation measures. Among the areas where research can expand adaptation opportunities is in devel- oping new technologies and management approaches and improving information on climate change, particularly at the regional and local scales where adaptation decisions will be made. Chapter 7 discusses in greater detail the major scientific and technological needs to promote effective adaptation to climate change. A key ques- tion decision makers might face is whether adoption and implementation of adap- tations should wait for such improved regional-scale information. One option is for decision makers to develop robust adaptation approaches that will be effective in a range of future conditions, regardless of the pace of scientific and technological developments—especially since the degree of certainty about climate change trajec- tories that most decision makers desire is unlikely to be forthcoming. Because of the considerable uncertainty regarding regional-scale climate change impacts, many stakeholders addressing climate change have expressed frustration with the lack of agreement on projections across global climate models as well as with these models’ low spatial resolution. Research should aim to improve the resolution and accuracy of climate modeling and thereby increase confidence in the projections, particularly where consideration of adaptation options has identified specific infor- mational needs. However, it is important to recognize that many adaptation decisions do not require precise forecasts of future conditions. For example, adaptations that incorporate flexibility, robustness (see discussion on robust decision making), or are hedging strategies may be effective under a wide variety of possible changes in cli- mate (as well as under current climate conditions). The adoption of such adaptations need not await improved accuracy in climate predictions. Some decisions such as on infrastructure or other investments with a long lifetime can benefit from more pre- cise climate projections. For such decisions, stakeholders need to weigh whether it is better to make a decision based on the current state of science or delay in the hope of having more precise projections in the future. Stakeholders should consider that while 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E bOx 4.8 Case Study in Innovative Adaptation: The National Flood Insurance Program New mechanisms for public-private partnerships in adaptation measures are needed, particularly in reducing future losses from floods and hurricanes associated with climate change. Insurers provide private-sector financial protection to those at risk from potentially large catastrophic losses (e.g., due to earthquake, hurricanes, or terrorist attack) by charging a fee (premium) to those who seek such protec- tion and, in turn, agreeing to pay all or a portion of the financial losses incurred in the event. Insurers that write policies for a large number of properties in a single geographical area face the possibility of large losses from a single event. The amount of coverage that an insurance company is willing to offer depends on the firm’s capital management, regulatory approvals of rates, availability and price of risk transfer instruments, and the insurer’s appetite for risk. Insurance in the United States is regulated at the state level, with the principal authority residing with insurance commissioners. Insurance commissioners often regard solvency as a principal objective for insurers, even if it means requiring higher premiums or other insurer adjustments (e.g., reducing their catastrophe exposures). State governments also have created and operated catastrophe insurance programs following large-scale disasters to supplement private insurance and reinsurance. Private- and public-sector insurers could play a role in encouraging adaptation to climate change risks in flood- and hurricane-prone areas.1 This could be done by increasing insurance premiums to better reflect the value of the risk. Insurance premiums could be set at a price that captures the value of the asset as well as the level of risk present. Establishing premiums in this way would provide signals to individuals about the level of hazards they face and could encourage them to engage in cost-ef- fective adaptation measures to reduce their vulnerability to catastrophes. Risk-based premiums could also reflect the cost that capital insurers need to integrate into their pricing to ensure adequate return to their investors. The application of this approach would provide a clear signal of likely damage to those currently residing in areas subject to natural disasters and those who are considering moving into these regions. Risk-based premiums would also enable insurers to provide discounts to homeowners and businesses that invest in cost-effective loss-reduction actions. If insurance premiums are not risk-based, insurers have no economic incentive to offer such discounts. In fact, they prefer not to offer coverage to these property owners at all because it is a losing proposition in the long run. In the context of the National Flood Insurance Program, applying this approach would require more accurate flood maps than currently exist. A recent National Research Council report (2009b) highlights the need for the Federal Emergency Management Agency (FEMA) to collaborate with federal, state, and local government agencies in this regard. The risks associated with losses from hurricanes and flooding may be higher than current estimates if there is an increase in the intensity of hurricanes or a higher-than-anticipated sea level rise caused by climate change during the next 10 or 20 years. Pursuing risk-based premiums could dissuade development of hazard-prone areas, but it could have high, unexpected costs for those already living in these locations. The value of land in high-hazard zones has a wide range. It may be desirable, beachfront property prone to erosion; but it could be land 

Managing the Climate Challenge that is affordable because it is vulnerable to flooding. Therefore, to address issues of equity and afford- ability, financing for increased premiums could come through general public funding for homeowners currently residing in hazard-prone areas, particularly low-income uninsured or inadequately insured homeowners, rather than through insurance premium subsidies. The drawback of this provision is that it could discourage adaptation among residents of hazard- prone areas. As discussed in the next section, regulations imposed by state insurance commissioners keep premiums in many hurricane-prone regions artificially lower than the risk-based level, encouraging maladaptive behavior. If residents in these areas were provided with financial assistance from public sources to purchase insurance, it could directly encourage development in hazard-prone areas and exacerbate the potential for catastrophic losses from future disasters. The complexity involved in adjusting insurance premiums, addressing concerns about equity, and accounting for behavioral biases suggests that innovative strategies are needed to encourage individuals to adopt cost-effective loss-reduction measures. Two possible complementary measures for dealing with this problem could be long-term contracts and well-enforced building codes. Long­Term Contracts for Encouraging Adaptation Two types of long-term contracts could encourage individuals to invest in adaptation measures: long-term flood insurance and long-term loans. Today, flood insurance is only offered as an annual contract, and many property owners would be reluctant to incur the costs even if they received a premium discount the next year. If property owners underweight the future, or only focus on the expected reduction in losses for the next several years, they would not want to incur the up-front cost of an adaptation measure. An alternative approach, then, would be a 20-year flood insurance policy that would tie the contract to the property rather than to the individual. Long­Term Home Improvement Loans The second suggested measure would provide long-term home improvement loans, tied to the home’s mortgage,for reducing vulnerability to climate change impacts.Such loans could be incorporated as part of the mortgage at a lower interest rate. A commercial bank would have a financial incentive to provide this type of loan: by linking the adaptation expenditures to the structure rather than to the current property owner, the annual payments would be lower, making the loan more attractive to mortgagees. The bank would be more fully protected against a catastrophic loss to the property, and FEMA’s potential loss from a major flood would be reduced because of the investment in adaptation. These adaptation loans would constitute a new financial product, and the general public would see fewer tax dollars spent on disaster relief (Kunreuther and Michel-Kerjan, 2009). 1For a more detailed discussion of these principles see Kunreuther and Michel-Kerjan (2009). 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E the science of climate change projections can be expected to improve (e.g., as the models and techniques for analyzing multiple model projections improve), substantial enhancements in climate projection science may take many years or decades to be realized. Consequently, delaying adaptations in anticipation of improved science can increase risk, for example, by delaying taking measures to reduce exposure to climate hazards (Barsugli et al., 2009). Therefore, it remains necessary to evaluate the tradeoffs between acting based on the current state of science versus delaying in hope of hav- ing improvements (ACC: Informing an Effective Response to Climate Change, NRC 2010a; Barsugli et al., 2009). CONCLuSIONS Adaptation to the inevitable impacts of a changing climate has emerged as a pressing concern at all levels of government, but actions are still hampered by lack of engage- ment, lack of resources, lack of adaptation-related research, poor understanding of vulnerability, and limited capacity to improve these conditions in the face of compet- ing policy priorities. Recent developments—the emergence of scientific consensus on causes and long-term trends in climate change; evidence that climate change impacts are already under way; realization that greater changes are coming, even if their timing and magnitude remain uncertain; and recognition that the past is no longer a reliable guide for the future—have validated the need for adaptation planning to manage risk. The existing barriers to adaptation illustrate that, without a well-integrated, compre- hensive planning process and an adaptive risk-management approach, the United States is ill prepared at this time to efficiently and effectively deal with climate change impacts. Clear strategies and coordination across agencies and all scales of government within the United States will be essential to leverage limited resources; avoid redundant or conflicting projects, mandates, and guidelines; improve understanding of changing conditions; overcome behavior-based limitations to the capacity to adapt; and encour- age learning as part of the policy-making process. Many states and municipalities have developed strategies and plans to adapt to climate change. These experiences have provided valuable insight into effective planning for adaptation, contributed to build- ing the nation’s adaptive capacity, and identified some win-win solutions to reduce the impacts of climate change. In general, risk-management approaches to adaptation planning and action do not re- quire a high level of precision about longer-term impacts of climate change, because they seek robust responses to a range of possible risks over time. Due to uncertainties 

Managing the Climate Challenge about future impacts and contexts, risk-management approaches can assist planning and decision making because such approaches tend to emphasize options that offer co-benefits, that is, that have benefits for reducing sustainable development stresses as well as for improving the ability to cope with climate change. Conclusion: A risk-management approach provides an appropriate framework for assessing the costs and benefits of adaptation options and prioritizing adaptation activities. Conclusion: Governments, individuals, and organizations that are or may be affected by climate change need to begin to adapt by assessing their current and future vulnerabilities and developing adaptation strategies and plans. New York City provides an excellent example of ways to structure a public process for setting adaptation priorities and of the vital role of leadership in managing such processes. Conclusion: An adaptation strategy needs to define a clear set of objectives that are focused on building adaptive capacity and reducing risk over multiple time frames, sectors, and scales. It needs to engage a wide range of participants, including those who are vulnerable and those who will be responsible for implementing the strategy. The success of the strategy will at least in part depend on the ability to engage both public and private sectors, to provide incentives for adaptive behavior, to communicate both risks and opportunities, and to prepare for gradual changes as well as low-probability/high-impact extreme events. Conclusion: An adaptation plan to implement this strategy needs to include the following: • An assessment of vulnerabilities in the context of other existing stresses, and the identification of adaptation options that are consistent with achieving broad societal objectives, including economic and environmental sustainability goals. • A consistent methodology to analyze and evaluate adaptation options, including opportunities to “mainstream” adaptations within existing pro- grams and processes and eliminate existing incentives for “maladaptive” behaviors. This should include consideration of the following: o Benefits (effectiveness) of adaptation, including reducing vulnerability to climate change impacts; o Co-benefits: positive effects on other systems or sectors; o Adverse impacts: negative effects on other systems or sectors; 

A D A P T I N G T O T H E I M PA C T S O F C L I M AT E C H A N G E o Costs to implement the adaptations; o Overcoming barriers to adoption of the adaptations; and o Limits to adaptation: At what magnitude of climate change would the adaptations become ineffective? • A plan for monitoring and evaluation of the adaptations in order to facili- tate adaptive management of risks, learn from experience, and build adap- tive capacity. 

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Across the United States, impacts of climate change are already evident. Heat waves have become more frequent and intense, cold extremes have become less frequent, and patterns of rainfall are likely changing. The proportion of precipitation that falls as rain rather than snow has increased across the western United States and Arctic sea ice has been reduced significantly. Sea level has been rising faster than at any time in recent history, threatening the natural and built environments on the coasts. Even if emissions of greenhouse gases were substantially reduced now, climate change and its resulting impacts would continue for some time to come.

To date, decisions related to the management and protection of the nation's people, resources, and infrastructure have been based on records in the recent past, when climate was relatively stable. Adapting to the Impacts of Climate Change, part of the congressionally requested America's Climate Choices suite of studies, calls for a new paradigm-one that considers a range of possible future climate conditions and impacts that may be well outside the realm of past experience.

Adaptation requires actions from many decision makers in federal, state, tribal, and local governments; the private sector; non-governmental organizations; and community groups. However, current efforts are hampered by a lack of solid information about the benefits, costs, and effectiveness of various adaptation options; climate information on regional and local scales; and a lack of coordination. Adapting to the Impacts of Climate Change calls for a national adaptation strategy that provides needed technical and scientific resources, incentives to begin adaptation planning, guidance across jurisdictions, shared lessons learned, and support of scientific research to expand knowledge of impacts and adaptation.

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