by Judith Curry
The Hearing on Policy-Relevant Climate Issues in Context is now beginning.
The link to the Hearing is [here], it is being webcast live (the webcast will be archived).
I was asked to respond to the following three questions:
• Summarize your views on the most important policy-relevant climate science issues facing decision-makers. What are the key areas of agreement and disagreement? What is the state of the science and associated strengths and weaknesses on key policy relevant issues, such as attribution, modeling and observations, and climate sensitivity?
• Describe the state of the science on the linkages between climate change and extreme weather. Include a discussion on the key uncertainties of these connections and describe how such uncertainties are treated in the public discussion of extreme weather events. What is needed to reduce misconceptions surrounding this scientific discipline?
• Include a broad discussion of uncertainties within climate change science, specifically addressing challenges and opportunities related to decision-making under uncertainty, including how such uncertainties are conveyed to policymakers and the public.
A daunting assignment. The complete text of my testimony can be found [curry testimony 2013 Il].
My verbal testimony is provided below (limited to 5 minutes).
JC’s verbal testimony
I would like to thank the Subcommittee for the opportunity to offer testimony this morning. My name is Judith Curry, I’m Chair of the School of Earth and Atmospheric Sciences at Georgia Tech. For the past 30 years, I’ve conducted research on topics that include climate feedback processes in the Arctic, the role of clouds and aerosols in the climate system, and the impact of climate change on hurricanes.
As President of a small company Climate Forecast Applications Network, I have worked with decision makers on climate impact assessments and using short-term climate forecasts to support adaptive management.
I’m also proprietor of the weblog Climate Etc. For the past several years, I’ve been promoting dialogue across the full spectrum of beliefs and opinion on the climate debate. I’ve learned about the complex reasons that intelligent, educated and well-informed people disagree on the subject of climate change, as well as tactics used by both sides to try to gain political advantage in the debate.
Through my company, I’ve learned about the complexity of different decisions that depend on weather and climate information. I’ve learned the importance of careful determination and communication of forecast uncertainty, and the added challenges associated with predicting extreme weather events. I have found that the worst prediction outcome is a prediction issued with a high level of confidence that turns out to be wrong; a close second is missing the possibility of an extreme event.
If all other things remain equal, it is clear that adding more carbon dioxide to the atmosphere will warm the planet. However the real difficulty is that nothing remains equal, and reliable prediction of the impact of carbon dioxide on the climate requires that we better understand natural climate variability.
My written testimony summarizes the evidence for, and against, the hypothesis that humans are playing a dominant role in global warming. I’ll make no attempt to summarize this evidence in my brief comments this morning. I will state that there are major uncertainties in many of the key observational data sets, particularly before 1980. There are also major uncertainties in climate models, particularly with regards to the treatments of clouds and the multidecadal ocean oscillations.
The prospect of increased frequency or severity of extreme weather in a warmer climate is potentially the most serious near term impact of climate change. A recent report from the Intergovernmental Panel on Climate Change found limited observational evidence for worsening of most types of extreme weather events. Attempts to determine the role of global warming in extreme weather events is complicated by the rarity of these events and also by their dependence on natural weather and climate regimes that are simulated poorly by climate models.
Given these uncertainties, there would seem to be plenty of scope for disagreement among scientists. Nevertheless, the consensus about dangerous anthropogenic climate change is portrayed as nearly total among climate scientists. Further, the consensus has been endorsed by all of the relevant national and international science academies and scientific societies.
I have been trying to understand how there can be such a strong consensus given these uncertainties. How to reason about uncertainties in the complex climate system is neither simple nor obvious. Scientific debates involve controversies over the value and importance of particular classes of evidence, failure to account for indeterminacy and ignorance, as well as disagreement about the appropriate logical framework for assessing the evidence.
For the past three years, I’ve been working towards understanding the dynamics of uncertainty at the climate science-policy interface. This research has led me to question whether these dynamics are operating in a manner that is healthy for either the science or the policy process.
The climate community has worked for more than 20 years to establish a scientific consensus on anthropogenic climate change. The IPCC’s consensus building process played a useful role in the early synthesis of the scientific knowledge about dangerous anthropogenic climate change. However, I have argued that the ongoing scientific consensus seeking process has had the unintended consequence of oversimplifying both the problem and its solutions, introducing biases into the both the science and related decision making processes.
When uncertainty is not well characterized and there is concern about ‘unknown unknowns,’ there is increasing danger of getting the wrong answer and optimizing for the wrong thing. I have argued in favor of abandoning the scientific consensus seeking approach in favor of open debate and discussion of a broad range of policy options on the issues surrounding climate change.
There are frameworks for decision making under deep uncertainty that accept uncertainty and dissent as key elements of the decision making process. Rather than choosing an optimal policy based on a scientific consensus, decision makers can design robust and flexible policy strategies that are more transparent and democratic, and avoid the hubris of pretending to know what will happen in the future.
The politicization of the climate change issue presents daunting challenges to climate science and scientists.
I would like to close with the reminder that uncertainty about the future climate is a two-edged sword. There are two situations to avoid: i) acting on the basis of a highly confident statement about the future that turns out to be wrong; and ii) missing the possibility of an extreme, catastrophic outcome. Avoiding both of these situations requires much deeper and better assessment of uncertainties and areas of ignorance, as well as creating a broader range of future scenarios than is currently provided by climate models.
This concludes my testimony.
JC comments: the text of this post was prepared prior to the start of the hearing, I am pushing the ‘publish’ button right as the hearing starts.