by Judith Curry
“Rather than justifying a lack of response to climate change, the emphasis on uncertainty enlarges the risk and reinforces the responsibility for pursuing successful long-term mitigation policy,” according to a 2010 analysis by researchers at Sandia National Laboratory.
All things considered, alarmism seems like common sense to me.
William Pentland has an article at Forbes entitled “The case for climate-change alarmism.” Some excerpts:
For better or worse, uncertainty pervades projections of global warming. Historically, this uncertainty has eroded support for implementing climate-change policies, but that may soon change – and dramatically so.
This may seem counter-intuitive, but only if you haven’t heard of climate-change’s “fat tail.” To put the significance of this fat tail in perspective, the “probability distribution representing the uncertainty in expected climate change implies that the risk of catastrophic outcome is more than forty thousand times more probable than that from an asteroid collision with the earth,” according to a recent report, “A Deeper Look at Climate Change and National Security,” by researchers at Sandia National Laboratory in New Mexico.
This has vast implications for how we manage the potential risks posed by climate change. Simply put, “the planetary welfare effect of climate changes . . . implies a non-negligible probability of worldwide catastrophe,” according toMartin Weitzman, a professor of economics at Harvard University and a pioneer of the so-called “Dismal Theorem.”
Climate change’s fat tail makes the likelihood of rare events more so. The distinguishing feature of a power law distribution is “not only that there are many small events but that the numerous tiny events coexist with a few very large ones,” according to Albert-Lászlí Barabási, a physicist at the University of Notre Dame and author of Linked: The New Science Of Networks.
Carolyn Kousky, an economist at Resources for the Future, has explained that:
Traditional responses to the risk of extreme events are of limited value in mitigating risks of a mega-catastrophe. The underlying changes in the climatic system could not be reversed over any time scale relevant for decision-makers, limiting the efficacy of traditional recovery measures. Insurance markets will not function for these risks as they violate three key conditions of insurability: independent and identical losses, feasible premiums, and determinability of losses. Impacts could be difficult to smooth over time, even for governments.
Uncertainty is intrinsic to complex systems like Earth’s climate, but in the context of catastrophic climate change, this uncertainty is so severe that it is difficult to draw basic conclusions about how fat the fat tail is. According to Weitzman, it “is difficult to infer (or even to model accurately) the probabilities of events far outside the usual range of experience.”
Uncertainty, risk and (in)action
Last May, I did a post entitled Uncertainty, risk, and (in)action, where Weitzman’s paper was discussed. I suggest that those of you that are unfamiliar with that paper read that thread before engaging in the discussion here.
Decision making under deep uncertainty
The state of our knowledge about future climate change is such that the degree of uncertainty and the level of ignorance precludes formulating a PDF of outcomes, or even putting bounds on the outcomes with a high confidence level. Given this, expected utility approaches to decision making don’t make sense.
The issue of decision making under deep uncertainty was discussed in this post on Can we make good decisions under ignorance? Robert Smithson enumerated six options for decision makers faced with deep uncertainty, with the precautionary principle being one of the options.
Weitzman, Friedman and Pentland seem to assume that the best solution lies within the framework of the precautionary principle. Apart from whether or not the precautionary principle is the best option here, at the heart of this debate is the weak vs strong precautionary principle.
While there are many definitions and nuances to the precautionary principle, of particular relevance here is the concept of ‘strong’ versus ‘weak’ precaution (e.g. Gardiner 2006): under weak precaution, the burden of proof for justifying the need for action falls on those advocating precautionary action, whereas under strong precaution the burden of proof is on those who argue that the activity does not cause significant harm. That is, under the weak precautionary principle, uncertainty does NOT make the case stronger for action, whereby the under the strong precautionary principle, uncertainty arguably strengthens the case for action.
So a preference for weak versus strong precautionary principle is related to a tolerance for risk. In the previous threads, it was pointed out that people are loss avoiders, not risk avoiders. If this is true, the strong precautionary principle is a hard sell as the preferred option for decision making under deep uncertainty.
JC summary: It seems that the case for climate change alarmism rests on the following dubious and arguable premises:
1. It is appropriate to represent future climate change outcomes as a PDF or a power law. (JC’s opinion: it is appropriate to represent future climate change outcomes as possible scenarios, and that emphasis is needed on imagining scenarios on both tails, including possible dragon kings.)
2. Avoidance of future risk should drive the decision making process (JC opinion: loss avoidance is more important than risk avoidance).
3. The precautionary principle is the preferred option for decision making (JC opinion: the other options for decision making under deep uncertainty need to be considered and frankly make more sense to me.)
In closing, I here is a statement from my testimony last year:
Based upon the background knowledge that we have, the threat does not seem to be an existential one on the time scale of the 21st century, even in its most alarming incarnation. It is now up to the political process (international, national, and local) to decide how to contend with the climate problem. It seems more important that robust responses be formulated than to respond urgently with a policy that may fail to address the problem and whose unintended consequences have not been adequately explored.
Note: Michael Tobis has an article on this at his new blog, Planet 3.0. Check out the post, it has a very funny cartoon on “Easter Bunny Island”