by Judith Curry
In Part IV, we explored the kerfuffle surrounding Fred Pearce’s attribution of “the science is settled” to Gavin Schmidt. Kim summarizes it this way:
The great irony, as Shub has pointed out elsewhere, is that here we have alarmists fighting like cats and dogs to make sure it is well understood that the science is not settled.
Well, that is more of a reconciliation than any of us could have hoped for, for all of us to agree that the science is not settled. Even Joe Romm is incensed by the “science is settled” statement (see here and here). The title of Romm’s 2nd post “Fabricated quote used to discredit scientist” adds a whole new dimension: a scientist associated with the “science is settled” statement is discredited. Wow.
So where did “the science is settled” come from? Manacker provides some history. It seems that journos and politicians are the main ones using this phrase. But many scientists have used words that sound similar. There is at least one instance of a leading IPCC scientist using these words, that I am aware of.
Richard Somerville in his essay “A response to climate change denialism” states:
1. The essential findings of mainstream climate change science are firm. This is solid settled science. The world is warming. There are many kinds of evidence: air temperatures, ocean temperatures, melting ice, rising sea levels, and much more. Human activities are the main cause. The warming is not natural. It is not due to the sun, for example. We know this because we can measure the effect of man-made carbon dioxide and it is much stronger than that of the sun, which we also measure.
I suspect that if you dig, you could find this phrase again in some of those petition like statements that 255 NAS members, or whatever group, have signed (the most recent one being the gang of 18 letter. The closest statement I can find in this letter is:
Congress needs to understand that scientists have concluded, based on a systematic review of all of the evidence, that climate change caused by human activities raises serious risks to our national and economic security and our health both here and around the world. It’s time for Congress to move on to the policy debate.
This is really the crux of their statement, its time to start implementing policies. I give credit to the gang of 18 for not urging drastic emissions reductions as the only logical policy option (which previous such letters have done).
What is settled?
So what actually is “settled”? In my post “What we know with confidence” I took the list from the IPCC First Assessment Report:
We are certain of the following:
- there is a natural greenhouse effect which already keeps the Earth wanner than it would otherwise be
- emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth’s surface. The main greenhouse gas, water vapour, will increase in response to global warming and further enhance it
Unfortunately, some people (the Sky Dragon group) don’t want to accept the first point, and I have devoted a number of threads to clarifying this issue, which seems resolved for all but the Sky Dragon authors and publisher. We’re moving on.
That said, there are a whole host of uncertainties, many of which have been discussed in Climate Etc. uncertainty series. If the science isn’t settled, this implies that there are uncertainties (some of which are reducible and many which aren’t), ambiguities (competing explanations), and ignorance. Time to embrace the uncertainty monster.
Unsettled science can liberate the policy deadlock
“Settled science” just isn’t something that is going to happen with regards to understanding and predicting climate change. Settled science is important politically if you are pursing the “truth to power” linear model of policy making. This is a bad model for something as complex and uncertain as the climate system.
At the Lisbon Workshop, a conversation with Jeroen van der Sluijs illuminated how to use uncertainty in policy deliberations (note JVDS has written tons of papers on this general subject, this one is the best overview). Here are three general models for decision making, depending on the type and level of uncertainty/ignorance (below is the off the top of my head understanding):
• optimal decision making (truth to power): where the risk is well characterized by probabilities and statistical uncertainty, decisions can be optimized in terms of cost/loss, etc. Attempts to put pdfs on climate sensitivity and set a 2C threshold and an associated emissions target (e.g. the IPCC/UNFCCC strategy) falls in this category.
• robust decision making: where there is scenario uncertainty (see here), optimal decisions targeted at a most likely outcome are not robust. By scenario uncertainty i don’t particularly mean emissions scenarios, but rather the range of sensitivities combined with natural variabilities plus the possibilities for black swans and dragon kings (e.g. abrupt climate change). Robust policies are useful across the range of scenarios, with no regrets for the actions no matter which scenario eventually emerges. Robust decisions regarding energy policy are ones that also address economic, security or health issues. An example of a non robust energy policy is carbon sequestration (geologic): if one of the higher sensitivity scenarios does not emerge, you have sunk a bunch of $$ into this with no ancillary benefits, and added some potential environmental hazards. By this reasoning, carbon sequestration would make sense only once the scenario uncertainty is reduced.
• resilient decision making: where there is substantial ignorance, the only recourse is to increase overall societal resilience. An element of resilient decision making is flexibility in responding to new information as it becomes available, that may reduce ignorance. General adaptation measures and economic development fall under this category.
IMO this is a hugely valuable framework for pondering the policy options (note this comes from the postnormal science paradigm). Trying to force sensitivity into a pdf (take note James Annan) is not only bad reasoning, but detrimental to sound decision making and building political will.
Postmortem
The “truth to power” strategy has failed, a victim of the uncertainty monster. Gavin’s statement in the email:
You would be much better off trying to find common ground on policy ideas via co-benefits (on air pollution, energy security, public health water resources etc), than trying to get involved in irrelevant scientific ‘controversies’.
Sounds like Gavin is becoming interested in robust decision strategies. Its time for the climate scientist activists to drop the “truth to power” strategy and learn something about decision making under uncertainty. JVDS is a very good place to start.
So perhaps the Lisbon Workshop will catalyze things by Gavin’s absence (aided by Tallbloke and Pearce), towards a more rational discussion of policy options and abandoning the “truth to power” strategy. Admitting that the science isn’t settled makes it much more difficult to justify their dismissal of “deniers” that have increasingly nuanced arguments (I’m not talking about Sky Dragon here). This is the reconciliation that I want, anyways.