National Research Council
America's Climate Choices
Prepared by Michael Marien
 October 2011
America’s Climate Choices.  National Research Council (Committee on America’s Climate Choices; Albert Carnesale, Chancellor Emeritus of UCLA & Chair).  Washington: National Academies Press, May 2011, 118p, $29.95pb. with CD.  (
The final report of the authoritative Committee on America’s Climate Choices, which synthesizes current thinking about climate change.  Hundreds of books and reports have been published on the climate change problem.   Three reasons for this new report: 1) “the body of scientific knowledge about climate change is growing rapidly,” as is understanding of the nature and severity of potential consequences; 2) unlike most previous studies, this one “looks across the full range of response options and interactions among them”; 3) this work provides “action-oriented advice on what can be done to respond most effectively to climate change,” addressed to decision-makers at all levels who will influence America’s response.
In short, this is the most up-to-date and authoritative report on the climate change problem and what to do about it.  It is not technical, and should be essential reading for anyone seriously interested in the climate change problem and the future in general.   It also serves as an excellent companion to the OECD report, Towards Green Growth (GFB Book of the Month, Aug 2011).
A Summit to help frame the study on America’s Climate Choices was convened in March 2009, in response to a request from the U.S. Congress.  This led to four panel reports released in Sept 2010: Adapting to the Impacts of Climate Change (292p), Advancing the Science of Climate Change (528p), Informing an Effective Response to Climate Change (348p), and Limiting the Magnitude of Climate Change (276p).  The attached CD includes all four panel reports, along with 4-page Reports in Brief and promotional videos.

This final summation builds on the four panel reports and other sources to answer four overarching questions: 


1. What short-term effective actions can be taken?
2. What promising long-term strategies, investments, and opportunities could be pursued?
3. What are the major scientific and technological advances needed to better understand and respond to climate change? 
4. What are the major impediments (practical, institutional, economic, ethical, intergenerational) to responding effectively, and what can be done to overcome them?



Climate change is occurring, is very likely caused by human activities, and poses significant risks for a broad range of human and natural systems.”  In the Committee’s judgment, “the environmental, economic, and humanitarian risks of climate change indicate a pressing need for substantial action to limit the magnitude of climate change and to prepare to adapt to its impacts.”  Given the complexities of the climate system and the many factors that affect it, “we can expect always to be learning more and to be facing uncertainties regarding future risks.  This is not, however, a reason for inaction.”  Reasons why it is imprudent to delay action:

1. The faster emissions are reduced, the lower the risks posed by climate change and the less pressure there will be to make steeper and probably more expensive reductions later.
2. Waiting for unacceptable impacts to occur before taking action is unwise because the effects of greenhouse gas emissions do not fully manifest themselves for decades; once manifested, many of these changes will persist for hundreds or even thousands of years.
3. As regards new energy infrastructure, getting relevant incentives and policies in place as soon as possible will provide crucial guidance for investment decisions.
4. Risks associated with “business as usual” are much greater than risks of engaging in strong response efforts; many aspects of “overly ambitious” policy response could be reversed if needed, whereas adverse change in the climate system are much more difficult to undo.
America’s response to climate change is ultimately about making choices in the face of risks: choosing, for example, how, how much, and when to reduce greenhouse gas emissions and to increase the resilience of human and natural systems to climate change.  These choices will in turn influence the rate and magnitude of future climate change and its impact on people and many things that people care about.  Each course of action carries potential benefits and risks, only some of which can be fully anticipated and quantified.”


Observed and Future Climate Change

1. Earth is warming: “the average temperature of the Earth’s surface increased by about 1.4oF 0.8oC) over the past 100 years, with about 1.0oF (0.6oC) of this warming occurring over just the past three decades.”  In the absence of new policies, the IPCC projects an increase of 2.0 to 11.5oF by the end of the 21st century, with impacts growing over time.
2. The preponderance of the scientific evidence points to human activities as “the most likely cause for most of the global warming that has occurred over the last 50 years or so.”
3. The concentration of CO2 in the atmosphere, primarily due to fossil fuel burning, has increased markedly over the past 150 years, and “is now higher than at any time in at least 800,000 years”  4. “US average air temperature increased by more than 2oF over the past 50 years,
and total precipitation increased on average by about 5%
5. Sea level has risen along most of the US coast, and is already eroding shorelines, drowning wetlands, and threatening the build environment.
6. US precipitation patterns have changed: heavy downpours have become more frequent and intense; frequency of drought has increased in the southeastern and western US, and decreased in the Midwest and Great Plains.
7. The frequency of large wildfires and the length of the fire season have increased substantially in the western US and Alaska.  Permafrost temperatures have increased throughout Alaska since the late 1970s, damaging infrastructure.
8. More intense, frequent, and longer-lasting heat waves are expected, both globally and in the US.
“Physical and social impacts of climate change are expected to have substantial economic implications throughout the US, but these effects will be unevenly distributed across regions, populations, and sectors.”  In addition to potential impacts that can be identified, “there is a real possibility of impacts that have not been anticipated.”


Unique Challenges of Climate Change

1. Complex linkages among emissions, concentrations, climate changes, and impacts (the basic links in this chain are well understood, but some elements are much less so); but lack of certainty about the details is not a justification for inaction.
2. Significant time lags in the climate system (failure to reduce GHG emissions in the near-term will “lock in” a certain amount of climate change for decades, if not centuries).
3. There are also significant time lags in human response systems: GHG emissions are to a large extent built into societal infrastructure, human habits, and organizational routines; market incentives affecting capital investments leave little room for considering long-term consequences.
4. Risks, judgments about risk, and adaptation needs are highly variable across different contexts: different regions, economic sectors, and populations will experience different impacts.
5. Decisions affecting climate change are made at all levels of society, although “the federal government can play a critical leadership role in setting policies”.
6. “Limiting climate change requires global-scale efforts.”  There is wide agreement that substantial action is needed by all major GHG-emitting nations.  “It is clear that strong, credible US policies for reducing domestic emissions will help international-level efforts to do the same.”
7. “Climate change is one of multiple, interconnected challenges”; e.g., coastal areas are being affected not only by GHG-driven changes such as sea level ise and ocean acidification, but also by pollution runoff, invasive species, coastal development, and overfishing.
8. The costs and benefits of different courses of action are generally not well known: they are difficult to quantify, and the costs to limit climate change risks are immediate--whereas many benefits will occur elsewhere and affect future generations.
9. Many factors complicate and impede public understanding of climate change (most people rely on secondary sources of information, especially the mass media).
10. There will inevitably be additional risks and surprises: climate change could turn out to be more manageable than expected, but “it is also quite possible that it could be more severe, or have much more severe impacts” (there may also be “tipping points” in the climate system, where a small change pushes the system into a sudden and radical shift; currently, it is impossible to predict where or when such tipping points might occur).


Iterative Risk Management: A Framework for Making Choices
“The risks posed by climate change are diverse and in almost all cases are imperfectly understood.”  And the many complexities inherent to climate change make it difficult to define specific actions that are needed in an effective long-term response strategy.
Historically, humans have responded to changing environments in four ways:
1. Muddling Through (an ad hoc approach to decision making as choices arise);
2. The Precautionary Principle (avoiding potentially serious or irreversible environmental harm);
3. “Staying the Course” (not taking any action until the need is fully established);
4. Cost-Benefit Analysis (weighing potential outcomes of taking or not taking action).
“All of these approaches present serious drawbacks in the context of climate change.”  Muddling
Through makes it difficult to consider long-term consequences.  The Precautionary Principle reflects a substantial aversion to risk with little regard for present costs, while Staying the Course minimizes costs with little regard for the risks of climate change.  Cost-Benefit Analysis can provide some useful insights in some contexts, but many of the costs and benefits of climate change impacts are difficult or impossible to quantify.

An iterative risk management approach for making climate change-related decisions overcomes many of these limitations.”  Key features of the process:
1. It is not a single set of judgments are some point in time, but a process of ongoing assessment, action, reassessment, and response.
2. It can draw on multiple forms of input, but is not limited to single criterion such as risk avoidance or economic efficiency.  Decision criteria include risk reduction potential, feasibility, cost-effectiveness, ancillary costs/benefits, equity and fairness, international considerations, and robustness.
3. It assesses risks, identifies options that are robust across a range of possible futures, and revises those choices as new information emerges through a process of “adaptive governance.”
4. In cases of substantial uncertainty, a “portfolio approach” of multiple and Complementary actions can be pursued.
5. Similar principles have been proposed by other high-level advisory groups such as the IPCC, the UN Development Programmme, the World Bank, the Australian Greenhouse Office, the UK Climate Impacts Programme, and PlaNYC (New York’s sustainability and growth management initiative,
which includes a Climate Change Adaptation Task Force)

Key Elements of America's Climate Choices

1. Limiting the Magnitude of Climate Change: setting goals such as limiting global average temperature to 2oC, reducing global emissions, using emission offsets, reducing US emissions substantially over the coming decades (through pricing, regulations, subsidies, and education), and possibly geoengineering (which may have a role to play, but costs, benefits, and risks of “solar radiation management” are not well understood).
2. Reducing Vulnerability to Climate Change Impacts: mobilizing now for adaptation, an effective National Adaptation Strategy (planning is emerging from the bottom-up in the US, but is hampered by a lack of knowledge and resources), creating durable institutions that can revise and improve strategy over time.
3. Investing to Expand Options and Improve Choices: advancing scientific understanding and technology development (a coordinated federal portfolio of research programs is needed), more effective information systems to make new knowledge pay off, broad-based deliberative processes to assure public and private engagement with scientific analysis.
4. More International Engagement: “The US has a strong national interest in ensuring an effective global response to climate change…(because it) can be deeply affected by climate change impacts occurring elsewhere.”
5. An Integrated National Response:  coordination across levels of government and across organizations (dozens of federal agencies and other organizations are carrying out research and taking action on climate change).


This important summary report should be of global interest.  It not only surveys current scientific understanding of the climate change problem, but uniquely explains the “unique challenges” of climate change and introduces “iterative risk management” as the best approach for making necessary choices.  Also see the OECD summary report, Towards Green Growth, which presents a detailed (but complex!) vision for tackling both economic and environmental problems, and Understanding Earth’s Deep Past: Lessons for Our Climate Future by the National Research Council (National Academies Press, Sept 2011, 194p, $34pb), which warns that “As Earth continues to warm, it may be approaching a critical climate threshold beyond which rapid and potentially permanent—at least on a human timescale—changes not anticipated by climate models tuned to modern conditions may occur.”

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