Characterizing Risk in Climate Change Assessments Proceedings of a Workshop (2016) / Chapter Skim
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2 Characterizing and Communicating Risk
2 Characterizing and Communicating Risk
Pages 9-32
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. CONSEQUENCES OF RISK: A POLICY PERSPECTIVE Alice Hill of the National Security Council (NSC)
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These efforts are "hard work," Hill commented, because the risks are not widely understood. Her experience speaking with groups -- including civil engineers, risk management specialists, infrastructure owners and operators, and policy makers -- has shown her that very few have read the previous climate assessments.
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assets and to environmental and economic systems. In short, Hill concluded, it is essential that the NCA4 deliver very clearly the message that changes in the Earth's climate are virtually irreversible in the absence of engineering solutions that do not currently exist, and some will occur even if greenhouse gas emissions are cut entirely today.
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Climate models are designed to use physical principles, constrained by past data on the Earth's systems, to produce simulations of future outcomes. They make it possible to test hypotheses about what might happen under varying sets of assumptions regarding specific variables, but the calculations must be "run" multiple times with different inputs (initial conditions and uncertain model parameters)
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Widespread crop failure or ice sheet collapse "can certainly not be ruled out," Sanderson noted, but they are subject to greater model uncertainty. He noted that multiple models contribute to confidence in the forecast for increasing heat waves.
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Climate scientists address this uncertainty using general circulation climate models, a particular type of climate model that calculates atmospheric circulation to represent the behavior of the climate. Researchers look for agreement among such models to assess how likely an outcome is.
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"This is not a complex feedback," Sanderson noted, "but it means that the Earth's sensitivity changes as you move into the future." 2. Incorporate critical carbon cycle feedbacks into current models.
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In the first example, Kopp and his colleagues combined econometric approaches to assessing relationships between humans and physical climate using probability distributions for local climate changes. They focused on sectors for which a large body of empirical data exists: agricultural production, health, labor productivity, energy demand, coastal buildings and infrastructure, and crime and civil conflict.
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Kopp also summarized an example presented in a second study, in which he and colleagues described a way that local stakeholders can use uncertain projections to support decision making. Kopp and his colleagues combined a variety of evidence -- including climate models, physical models of local effects, expert assessments, data on land water storage (water stored in the ground)
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. These figures are adapted from American Climate Prospectus maps prepared by Climate Prospectus (http://climateprospectus.org/ [August 2016]
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NOTES: A 1-in-20 year event assuming current population would result in 25,000 deaths. RCP stands for representative concentration pathways, which are distinct levels of greenhouse gas concentration in the atmosphere that could result in future differing levels of greenhouse gas emissions over time.
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Physical models can be used to determine the magnitude and timescale of physical changes that may occur, Kopp noted. Empirical models and process models for particular sectors can be used to assess how those physical changes may translate into economic costs.
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With climate change, however, which many policy makers do not accept as an important issue, effective framing would focus instead on moral considerations and the dramatic risks and costs the scientific information demonstrates. Leaders such as Pope Francis are in a position to address the moral considerations, but the NCA4 is ideal for addressing the risks and costs that can motivate people to act, Wilson noted.
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Wilson also had suggestions for framing the data itself. The NCA3 established some guidance for authors, such as • providing numerical, not just verbal, estimates; • using standardized likelihood ranges; • providing a confidence range for conclusions; and • highlighting low-probability/high-consequence events.
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. The third National Climate Assessment's coastal chapter: The making of an integrated assessment.
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For example, one suggested, the electrical community is very interested in information about the possibility that the frequency of extreme events affecting the power grid, such as ice storms and lightning events, will increase. The existing science may not indicate probabilities but can be very helpful in helping people understand what they need to prepare for and the approximate timeframe.
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Structured techniques for making decisions can help, Gregory explained. These techniques might include using diagrams to explore means and ends or identifying priorities for different objectives using decision trees, profiles of risk tolerance, or surveys of what people value.
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Uncertainty is a serious challenge, Gregory noted, which arose in almost every session of the workshop. The complexities of climate models and the results of studies are difficult to communicate in clear, simple terms.
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They also may be frustrated that their concerns appear to be ignored by decision makers. Thus the aims of communication should be to guide people in better understanding both the scientific information and their own values and to help decision makers design policy alternatives that are responsive to stakeholders' concerns.
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28 CHARACTERIZING RISK IN CLIMATE CHANGE ASSESSMENTS FIGURE 2-7 Perceived risk and benefit ratings. NOTE: Triangles and circles represent survey respondents' perceived ratings of risks and benefits.
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. 10Criteria air pollutants are the six air pollutants that are most common in the United States: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide.
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They used hourly data on emissions of sulfur dioxide and nitrogen oxides for every power plant that uses fossil fuels, which is collected by the Environmental Protection Agency. With these data they were able to derive actual or simulated information about the effects of interventions on an hourly basis.
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Azevedo and her colleagues were able to characterize the environmental and health benefits of wind and solar power using hourly data for thousands of power plants across the country by estimating the amount and type of power that would be displaced and calculating the benefits of that displacement. As one might expect, Azevedo explained, the results for solar power show that the locations that can provide the largest electricity output using solar panels are not the ones that can benefit the most.
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For example, the participant noted that during droughts in California, limitations in hydropower capacity can cause an increase in reliance on natural gas. Azevedo noted that the analysis is designed to identify optimal potential benefits across the country.
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