Deep and Shallow Uncertainty in Messaging Climate Change

This post draws on a recent RFF discussion paper by RFF Senior Fellow Roger Cooke, where he explores these topics in greater detail. Cooke is the Chauncey Starr Chair in Risk Analysis at RFF and lead author for Risk and Uncertainty in the recently released IPCC Fifth Assessment Report.

Present State of the Uncertainty Narrative

In 2010, the US National Research Council (NRC) illustrated reasoning under uncertainty about climate change using the calibrated uncertainty language of the 2005 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. The NRC report bases its first summary conclusion on “high confidence” (at least 8 out of 10) or “very high confidence” (at least 9 out of 10) in six (paraphrased) statements:

  1. Earth is warming.
  2. Most of the warming over the last several decades can be attributed to human activities.
  3. Natural climate variability … cannot explain or offset the long-term warming trend.
  4. Global warming is closely associated with a broad spectrum of other changes.
  5. Human-induced climate change and its impacts will continue for many decades.
  6. The ultimate magnitude of climate change and the severity of its impacts depend strongly on the actions that human societies take to respond to these risks.

What is the confidence that all these statements hold? In the non-formalized natural language it is not even clear whether “all statements have a 0.8 chance of being true” means “each statement has a 0.8 chance of being true” or “there is a 0.8 chance that all statements are true.”  Consider the second statement. Are the authors highly confident that “the earth is warming AND humans are responsible”, or are they highly confident that “GIVEN that the earth is warming, humans are responsible”? These are very different statements. Since the Earth’s warming is asserted in the first statement, perhaps the second statement is meant. In that case, the likelihood of both statements holding is the product of their individual likelihoods. If the first two statements enjoy “high confidence”, then both can hold with only “medium confidence”.

Suppose the Nuclear Regulatory Commission licensed nuclear reactors based on the finding that each reactor’s safety each year was “virtually certain” (99–100 percent probability). With 100 commercial nuclear reactors, each with a probability of 0.01 per year of a meltdown . . . well, do the math. That is the point: To reason under uncertainty you may have to do math. You can’t do it by the seat of the pants. I am very highly confident that all above statements hold, but I am 100 percent certain that this way of messaging uncertainty in climate change won’t help us get the uncertainty narrative right.

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This Week in the RFF Library Blog

Each week, we review the papers, studies, reports, and briefings posted at the “indispensable” RFF Library Blog, curated by RFF Librarian Chris Clotworthy. Check out this week’s highlights below:


The 2014 Fuels America Economic Impact Study: Methodology
A new industry report released today shows how the Renewable Fuel Standard (RFS) is creating jobs and significant economic impact. The Fuels America coalition released an economic impact study by John Dunham & Associates showing that the industry supports more than 850,000 American jobs and drives $184.5 billion of economic output. — via John Dunham & Assoc. for Fuels America

Hydraulic Fracturing: Meeting the Nation’s Energy Needs While Protecting Groundwater Resources
In the NGWA’s position paper, Hydraulic Fracturing: Meeting the Nation’s Energy Needs While Protecting Groundwater Resources, the Association discusses that poor water quality may not be a direct result from fracking. The study shows that water contamination and other drinking water and/or groundwater issues are instead the result of faulty casing installations, unsealed wells, poor management, accidents, and other instances where unsatisfactory practices or processes take place. — via National Groundwater Association

Draft California Communities Environmental Screening Tool v2.0 (CalEnviroScreen 2.0)
…The screening tool, called CalEnviroScreen, was developed by the Office of Environmental Health Hazard Assessment, a branch of Cal/EPA, to pinpoint the communities with the highest exposure and vulnerability to multiple environmental hazards, including polluted air and water, waste facilities and contaminated soil… — via California Environmental Protection Agency

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RFF ON THE ISSUES: Droughts and groundwater; North American energy

Droughts and Groundwater

Lawmakers in California recently proposed the nation’s first water efficiency standards for new toilets and faucets, which are expected to save the state 8.2 billion gallons of water in the first year. The standards should help relieve pressure on water providers in what is expected to be “a hot and dry future for the state.”

California’s drought “presents a catch-22 for the state and its residents,” writes RFF Fellow Yusuke Kuwayama in an article for Resources magazine. “Water shortages will increase reliance on declining groundwater supplies, but the unsustainable use of this resource has contributed to the severity of the drought.” He suggests that the creation of groundwater markets could serve the state’s “changing conditions and demands” while preventing large declines in water tables.

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Is the IPCC Government Approval Process Broken?

This post originally appeared on Robert Stavins’s blog, An Economic View of the Environment.

Over the past 5 years, I have dedicated an immense amount of time and effort to serving as the Co-Coordinating Lead Author (CLA) of Chapter 13, “International Cooperation:  Agreements and Instruments,” of Working Group III (Mitigation) of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC).  It has been an intense and exceptionally time-consuming process, which recently culminated in a grueling week spent in Berlin, Germany, April 5-13, 2014, at the government approval sessions, in which some 195 country delegations discussed, revised, and ultimately approved (line-by-line) the “Summary for Policymakers” (SPM), which condenses more than 2,000 pages of text from 15 chapters into an SPM document of 33 pages.  Several of the CLAs present with me in Berlin commented that given the nature and outcome of the week, the resulting document should probably be called the Summary by Policymakers, rather than the Summary for Policymakers.

Before returning to the topic of today’s blog entry — the SPM process and outcome — I want to emphasize that the IPCC’s Working Group III “Technical Summary” and the underlying Working Group III report of 15 chapters were completely untouched by the government approval process of the Summary for Policymakers.   So, the crucial IPCC products – the Technical Summary and the 15 chapters of WG 3 – retain their full scientific integrity, and they merit serious public attention.  Now, back to the SPM process and outcome…

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Research Questions for the Midterm CAFE Review: Will the Footprint-Based CAFE Standard Work as Expected?

This is the third in a series of blog posts by RFF’s transportation team that addresses some of the key research questions for the midterm CAFE review.

Source: iStockphoto

The first two blog posts in this series introduced the midterm review of the corporate average fuel economy (CAFE) standards and discussed unresolved issues for this review about the fuel efficiency gap. In this post, we focus on issues raised by the shift to vehicle footprint–based standards. Until the changes to the CAFE rules in 2012, all passenger cars were held to the same fuel economy standard (27.5 miles per gallon [mpg] from 1990 to 2011) and all light-duty trucks were held to a weaker standard (between 20 and 23 mpg during the same period). But before the standards were tightened in 2012, federal legislation in the late 2000s required the ruling agencies to base the new standards on a vehicle attribute or attributes related to fuel economy (known as attribute-based standards). The US Environmental Protection Agency and National Highway Traffic Safety Administration (NHTSA) now base the standards on a vehicle’s footprint, defined as the area between the four wheels, and they also maintain the car–truck distinction. Vehicles with a smaller footprint must meet a tighter standard than those with a larger footprint, and light-duty trucks still have a less stringent overall footprint standard than cars.

Before making this decision, the agencies considered several attributes on which to base the standards. European, Japanese, and Chinese standards depend on vehicle weight, with heavier vehicles allowed to have more lenient standards. One argument for the footprint standard used in the United States over the weight-based standard is that it would provide incentives for manufacturers to improve fuel economy by using lighter-weight materials. A weight-based standard would not provide the same incentive, because lighter vehicles would face a tighter standard. The agencies also argued that a footprint standard would force more technology for improved fuel economy across all vehicle sizes, with less incentive to downsize to meet the standard. Whether based on size or weight, the attribute-based standard has political appeal because it will have costs that fall more evenly on all manufacturers compared to a mpg-based standard that would tend to favor manufacturers with a smaller or lighter vehicle fleet. An attribute-based standard was also especially appealing to NHTSA, who was particularly concerned that, with so many large vehicles on the roads, downsizing new vehicles would result in more fatalities.

But will the footprint standard work as expected?  The effect of CAFE standards on traffic fatalities is highly controversial. Bigger and heavier vehicles are safer in single-vehicle accidents and are safer for their own occupants in multi-vehicle crashes. But drivers and passengers face greater risk in an accident with a larger or heavier vehicle than with a smaller or lighter one. Furthermore, NHTSA analysis recently concluded that reducing weight while holding footprint constant does not increase fatality risks; this is a major reason the agency favors the footprint-based standard. Read More

Flood Insurance Claims: A Fat Tail Getting Fatter

Floods remain some of the worst disasters around the world. They cause more property damage and insured losses than many other types of events. In the US, floods are primarily insured through the federally-run National Flood Insurance Program (NFIP). This program has been making the headlines recently as Congress tries to address the program’s massive debt from Hurricanes Katrina, Ike, and Sandy; homeowners bemoan high flood insurance costs; communities receive new flood maps suggesting flood risk has changed over time; and disaster victims wonder how to rebuild to prevent future losses and keep insurance costs manageable.

We have been examining the distribution of NFIP claims, provided by the Federal Emergency Management Agency to the Wharton Risk Center.  Individual claims are aggregated to census tracts and months, over the years 1978 to 2012. We find that this distribution is decidedly fat-tailed. This means that yearly losses can be hopelessly volatile and, as such, historical averages are not good predictors of future losses. For those more technically inclined, we have been doing this by fitting a Pareto distribution to the aggregate claims. Our estimation of the tail index gives an indication of the fatness of the tail. The smaller the tail index, the fatter the tail.

That flood claims are fat-tailed is, in and of itself, not so surprising. Many disaster losses have been found to exhibit fat tails. What is concerning, however, is that the tail of flood insurance claims seems to be getting fatter over the time period in our data. This would indicate the extremes are getting even more extreme.  One way to examine this is to use the so-called Hill estimator, which gives an estimate of the tail index (here, based on the largest 10% of claims), for each year. When we plot estimates of the tail index using this method, there is a clear downward trend, as seen in the figure below. Lower values, fatter tail. The blue diamonds are the yearly estimates and the black line is a fitted linear trend line to those estimates.

hill-years

We also looked at the tail index by state. We broke the data into two periods, 1978-1990 and 1990-2012, and estimated the tail index (using maximum likelihood) for each period for each state in the country. For all but a handful, the tail index is lower in the later period, indicating that the tail of the distribution of flood claims is fatter in the later period.

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What Do State Renewable Portfolio Standards Mean for Carbon Intensity?

RFF-DP-14-10-coverIn the last two decades, 31 states have passed renewable portfolio standards (RPS) into law that are aimed at increasing the portion of state energy that is sourced from renewable, typically non-carbon-emitting, resources. In many states, such standards were not explicitly meant to reduce greenhouse gas (GHG) emissions, although given the energy sources they promote (solar and wind, for example), emissions reductions are an expected result. The environmental economics literature, however, points out that RPS are far from the most efficient policy to reduce carbon emissions. In fact, previous econometric studies on early RPS implementation suggest that the standards have failed to decrease GHG emissions or even significantly increase renewable energy deployment. However, in a new RFF discussion paper, with RFF University Fellow Brent Sohngen of Ohio State University,  we find that RPS actually have reduced carbon emissions in the United States by around 4 percent at present, and that figure is increasing.

We used data between 1997 and 2010 to identify the drivers of state carbon intensity, measured in tons of carbon dioxide emissions per dollar of gross state product. After accounting for differences in economic structure and environmental factors, we find that RPS implementation reduces state carbon intensity, mainly through an increase in electricity prices, with a $0.01/KWh increase in electricity prices leading to an approximately 1 percent decrease in state carbon intensity. The relationship between the price of electricity and carbon intensity is slightly smaller but still significant in states that have passed RPS because these states already have lower initial carbon intensities than states without RPS, causing them to be less sensitive to additional changes in the price of electricity. In addition, the standard itself also has an effect on the carbon intensity, although the effect is statistically insignificant. 

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Twitter Q&A Roundup: Exploring the Local Impacts of Shale Gas Development

On April 10, RFF hosted a seminar on the benefits and costs of shale gas development as experienced by local communities, titled “Exploring the Local Impacts of Shale Gas Development.” As moderator of that event, I’ll attempt to tackle some of the questions posed by our Twitter audience during the event that we were unable to address during the live seminar due to time constraints.

Our calculations for numbers of round trips were determined primarily by dividing the amount of water needed to frack a well by the amount of water a single truck can hold. 

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RFF ON THE ISSUES: Mercury regulations upheld; Beijing pollution; Local shale impacts

Mercury Regulations Upheld

Last week, the US District Court of Appeals for the DC Circuit upheld the US Environmental Protection Agency’s (EPA’s) authority to enforce its Mercury and Air Toxics Standards (MATS). The court ruled that the standards are “substantively and procedurally valid,” despite concerns that the rules would severely increase electricity rates.

Various studies have attempted to predict the potential impacts of MATS. RFF’s Blair Beasley, Matt Woerman, Anthony PaulDallas Burtraw, and Karen Palmer attempted to reconcile the results of this research and found that the “studies that most closely match the regulatory requirements as laid out in the final MATS rule and do not include other proposed EPA regulations . . .[demonstrate] less severe impacts on the electricity market.”

Beijing Pollution

The rapid growth of Beijing’s economy, population, and energy use—along with pollution from surrounding provinces—is to blame for the city’s continued air quality problems, according to the Beijing Environmental Protection Research Institute. China’s government has drafted ambitious plans to cut future coal consumption, but challenges remain, including “big polluting industries and growth-obsessed local authorities.”

In an interview with Resources magazine, RFF Visiting Fellow Mun Ho suggests that changes in China’s demographics have facilitated support for more restrictive pollution policies: “[F]or a long time now, given the large-scale, low-income situation in China, growth has been the key priority. This is changing, now that China is developing more of a middle class. The emphasis now is on the quality of life. The quality of the environment, accordingly, is much higher on the agenda, but it is a difficult problem.”

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This Week in the RFF Library Blog

Each week, we review the papers, studies, reports, and briefings posted at the “indispensable” RFF Library Blog, curated by RFF Librarian Chris Clotworthy. Check out this week’s highlights below:


The End of China’s Coal Boom:  5 Facts You Should Know
Global greenhouse-gas emissions may peak before 2020 if China achieves a plan to drastically cut its coal use, reducing carbon production equivalent to Australian and Canadian output combined, Greenpeace says. — via Greenpeace

Fueling a New Order? The New Geopolitical and Security Consequences of Energy
The paper Fueling a New Order? The New Geopolitical and Security Consequences of Energy examines impacts of the major transformation in international energy markets that has begun. The United States is poised to overtake Saudi Arabia and Russia as the world’s largest oil producer and, combined with new developments in natural gas, is on track to become the dominant player in global energy markets. Meanwhile, China is in place to surpass the United States… — via Brookings Institution

National Environmental Policy Act: Little Information Exists on NEPA Analyses
Little information exists on the costs and benefits of completing NEPA analyses. Agencies do not routinely track the cost of completing NEPA analyses, and there is no governmentwide mechanism to do so, according to officials from CEQ, EPA, and other agencies GAO reviewed… — via U.S. Government Accountability Office

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