by Judith Curry
The U.S. National Climate Assessment and Development Advisory Committee (NCADAC) has released a draft of its report for public comment.
From the NCADC website:
The NCADAC, whose members are available here (and in the report), was established under the Department of Commerce in December 2010 and is supported through the National Oceanic and Atmospheric Administration (NOAA).
The NCADAC has engaged more than 240 authors in the creation of the report. The authors are acknowledged at the beginning of the chapters they co-authored.
Link [here] to download the report. I have read a few sections.
In the Executive Summary, first page, their argument can be represented by the first sentence of each of the paragraphs:
- Climate change is already affecting the American people.
- Many impacts associated with these changes are important to Americans’ health and livelihoods and the ecosystems that sustain us.
- Evidence for climate change abounds, from the top of the atmosphere to the depths of the oceans.
- U.S. average temperature has increased by about 1.5°F since 1895; more than 80% of this 21 increase has occurred since 1980.
- U.S. temperatures will continue to rise, with the next few decades projected to see another 2°F to 4°F of warming in most areas.
- The chances of record-breaking high temperature extremes will continue to increase as the climate continues to change.
- Human-induced climate change means much more than just hotter weather.
The word ‘uncertainty’ receives its first mention on p 17, here is how they deal with the issues associated with uncertainty:
Authors of this assessment were asked to approach it from the perspective of a decision-maker trying to limit risk to valued systems, resources, and communities (and to consider opportunities as well). For each chapter, they were asked to frame a number of key questions or issues that address the most important information needs of stakeholders, and consider the decisions stakeholders are facing. The criteria provided for identifying key vulnerabilities in their sector or region included: magnitude, timing, persistence/reversibility, distributional aspects, likelihood, and importance of impacts (based on the perceptions of relevant parties) as well as the potential for adaptation. For the purposes of this assessment, risk was defined as the product of likelihood and consequence, and authors were encouraged to think about these topics from both a quantitative and qualitative perspective, and to consider the influence of multiple stresses if possible.
The level of confidence the chapter authors have in the key findings they report is given in “traceable accounts” that accompany each chapter. A traceable account is intended to: 1) document the process the authors used to come to the conclusions in their key messages; 2) provide additional information to reviewers about the quality of the information used; and 3) allow traceability to data and resources. The authors have assessed a wide range of information in the scientific literature and previous technical reports. In assessing confidence, they have considered the strength and consistency of the observed evidence, the skill, range, and consistency of model projections, and insights about processes and climate from peer-reviewed sources.
When it is considered scientifically justified to report the likelihood of particular impacts within the range of possible outcomes, this report takes a plain-language approach to expressing the expert judgment of the author team based on the best available evidence. For example, an outcome termed “likely” has at least a two-thirds chance of occurring; an outcome termed “very likely,” at least a 90% chance. Key sources of information used to develop these characterizations of uncertainty are referenced. Draft for Public Comment
Addressing Incomplete Scientific Understanding
Within each traceable account, the authors identify areas where a lack of information and/or scientific uncertainty limits their ability to estimate future climate change and its impacts. The section on “An Agenda for Climate Impacts Science” at the end of this report highlights some of the areas suggested for additional research.
I then skipped down to the chapter 29 Research Agenda for Climate Change Science. The highlighted research goals are:
1. Deepen understanding of the climate system, feedbacks, and impacts.
- Better understanding of important sources of uncertainty and feedbacks in the climate system such as clouds, changes in land and sea ice, aerosols, land use and land cover, thresholds and feedbacks, and the means by which ocean dynamics affect changes in the climate system;
- Advancing capacity to project biogeophysical changes in the nation’s ecosystems and associated services (such as food availability and security, protection of biodiversity, healthy wetlands, and abundant fresh water) or the nature, timing, and location of terrestrial permafrost and methane release processes;
- Improved understanding of the interactions of climate change and natural variability at multiple time scales, including seasonal to decadal changes (and consideration of the El Niño Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation, etc.), extreme events (hurricanes, droughts, and floods), potential changes in ocean circulation related to climate change, and the global transfer of heat laterally and toward the poles;
- Improved, and more detailed, projections of the rate of change in oceanic pH, carbonate saturation, and attendant acidification and its consequences for the marine 36 biosphere and food chain;
- Research to improve our nation’s ability to understand the cumulative and synergistic relationships between climate change and numerous human-caused stressors at appropriate scales, including multiple stresses affecting the climate system (including concentrations of heat-trapping gases and particulates in the atmosphere, changes in land use and land cover, shifts in human cultural behavior or demographics, or changes in economic factors).
- Experiments on the effects of multiple stressors within and between social, physical, and ecological systems in the context of global change;
- Better understanding of the potential for crossing thresholds and tipping points in affected climate systems, along with development of indicators that allow for anticipation 10 of abrupt changes and extreme events in the context of a changing climate.
- Assessing the relative importance of different types of uncertainty that affect various decision-making contexts, including uncertainties regarding vulnerability, different impacts models, future socioeconomic factors, possible changes in governance structures, decision-making protocols, and regional climate change.
- Better long-term and regional scale projections of sea level changes
- More specific regional information about the role of soil moisture, groundwater recharge, and evapotranspiration in the hydrologic cycle and water supply availability.
2. Develop local, regional, national, and international options to adapt to climate change.
3. Explore options and actions that reduce the rate and magnitude of climate change.
4. Maintain, extend, expand, and improve the observations and data systems essential to understanding climate change and responding to it.
5. Inform and enable decision-makers to address the challenges of climate change and its consequences.
6. Capacity Building, Education, and Workforce Development
7. Enhance scenarios to include essential attributes of coupled human and natural systems.
JC comments: I have only read a few chapters, but the impression that I have is this. The document is framed around the assumption that climate change is caused by anthropogenic forcing, and that future adverse impacts are extrapolated through climate model projections. Any characterization of uncertainty seems like an afterthought.
Chapter 29 has some good material regarding for what is needed for better understanding of all this. Personally, I would have made Chapter 29 the first chapter. A good historical analysis of the regional impacts of climate variability would be very important, but the few chapters that I read deal more with ‘projections’ and interpretations of past variability framed in context of anthropogenic forcing.
I am very concerned that the highly confident story being told here has enormous potential to mislead decision makers.
The authors have the opportunity to do a better job, but I suspect that this is pretty much written in stone at this point, with a few minor changes to be made in response to public comments.
Moderation note: Lets have a productive, focused discussion on this topic. A prerequisite for commenting on this thread is to read at least one of the sections in this report and comment on it. If you want to ‘spout off’ on this topic without having read any of the sections of the report, please do so on the open thread.
Update: Rob Bradley reminds us of the alternative impact assessment report by Cato.