Posts Tagged ‘risk’

Climate change as a matter of risk management requires different choices in communication

June 11, 2018

Rowan Sutton just published a very short article (an “idea”) in ESDD entitled “a simple proposal to improve the contribution of IPCC WG1 to the assessment and communication of climate change risks”. From a risk management point of view a focus solely on the most likely outcome is not recommended, especially when the impacts increase sharply towards one end of the scale.


A common measure of risk is likelihood x impact (Fig 1). It is standard practice in risk assessment to highlight both the most likely impacts and low likelihood high impact scenarios. Such scenarios merit specific attention because the associated costs can be extremely high, so decision makers need to know about them. It follows that WGI has a responsibility to assess and communicate explicitly the scientific evidence concerning potential high impact scenarios, even when the likelihood of occurrence is assessed to be small. In past reports the assessment of key parameters by WG1 has focussed overwhelmingly on likely ranges only. When information has been provided about the tails of distributions only likelihoods have been communicated using terms – following the IPCC’s uncertainty guidance (Mastrandrea et al, 2010) – such as “very unlikely” or “extremely unlikely”: a clear steer that policy makers should largely ignore such possibilities. But this is wrong. Policy makers care about risk not likelihood alone. The IPCC’s uncertainty guidance ignores impact and is symmetric with respect to high or low impact scenarios; this is inappropriate for the communication of risk (Fig 1).

Figure 1: A schematic representation of how climate change risk depends on equilibrium climate sensitivity (ECS).

Some will argue that the WGII report is needed to provide information on impacts. For detailed information this is certainly the case, but the general shape of the damage function for a large basket of impacts (Fig 1) is insensitive to such details, and is all that is needed to justify WGI providing a much more thorough assessment of relevant scenarios. Other critics will suggest that for WGI to identify high impact scenarios explicitly would constitute scaremongering; this concern is no doubt one reason why previous WGI reports have focused so much on the likely range. But it is misguided. Policy makers need to know about high impact scenarios and WGI has a responsibility to contribute its considerable expertise to making the appropriate assessments.

A very similar point has been made by Kerry Emanuel in his post “Tail risk vs Alarmism” on CCNF:

In assessing the event risk component of climate change, we have, I would argue, a strong professional obligation to estimate and portray the entire probability distribution to the best of our ability. This means talking not just about the most probable middle of the distribution, but also the lower probability high-end risk tail, because the outcome function is very high there.


But there are strong cultural biases running against any discussion of this kind of tail risk, at least in the realm of climate science. The legitimate fear that the public will interpret any discussion whatsoever of tail risk as a deliberate attempt to scare people into action, or to achieve some other ulterior or nefarious goal, is enough to make almost all scientists shy away from any talk of tail risk and stick to the safe high ground of the middle of the probability distribution. The accusation of “alarmism” is quite effective in making scientists skittish in conveying tail risk, and talking about the tail of the distribution is a sure recipe to be so labelled.

Hans Custers schreef een kort Nederlandstalig blog over Sutton’s artikel.


It’s what we know that’s most important

November 11, 2010

If we’re to be out there, we also have to be smart.

Chris Mooney offers some thoughts and advice based on climate scientists’ efforts to increase their engagement with the public and explain -and if necessary defend- the science.

Facts and framing: Both are important

When it comes to science communication, the facts are the baseline from which one absolutely cannot stray; but at the same time, we have to be aware that people respond most strongly to the frame.

Uncertainty and risk

Remember that the political attack is also largely scientific in nature, at least in terms of its framing. It exaggerates uncertainty about particular scientific studies (…) in order to distract from the big picture.

So any scientist walking into this context had better be ready for one obvious trap: Being lured into talking about uncertainty to the detriment of what we actually know.

This is in sharp contrast to what Judith Curry is pushing for: Framing the issues in terms of uncertainty and stressing what we don’t know. I am in firm agreement with Chris Mooney here. Judith’s strategy is a dead end in terms of increasing the public’s knowledge about climate change.

Conversations about uncertainty invoke a frame which in the public mind is easily confused with doubt. Non-scientists have a very different perception of uncertainty than scientists. Framing what we know and don’t know in terms of risk is much more useful in getting the message across, because it leaves less room for misinterpretation (there is less of a gap in how this term is understood, whereas “uncertain” to a layperson means “I don’t know”).

Let me stress that I’m not advocating to downplay the uncertainties. But emphasizing (let alone exaggerating) them is not the road to increase people’s understanding of the issue, where what we do know is much more important to convey (if you goal is to increase the public’s knowledge of the scientific knowledge). It is thereby useful to distinguish the different levels of confidence of the knowledge: Some aspects are virtually certain, whereas others have a wider confidence interval.

This also depends on the level of knowledge of the public. If your audience doesn’t even grasp the basics and has a very twisted view of what is scientifically known, it’s most useful to keep your message simple and focussed on the broad outline of what we do know. As Neven suggested to Judith Curry, who is invited by the Republicans to testify for the US House of Representatives:

Be sure to tell them AGW is real. Start with that and end with that, please.

Herman Daly makes the point very well that the basics of what we know is most important, “at least as to the thrust and direction of policy”. Consider e.g. this quote that I’ve often used since:

To make the point more simply, if you jump out of an airplane you need a crude parachute more than an accurate altimeter.

If politicians or members of the public aren’t even aware that they’re (very, very slowly) jumping out of an airplane (the situation of which can only very, very slowly be changed), then details about the accuracy of the altimeter are of far less importance than telling them they’re about to go mid-air (albeit in slow motion). Don’t tell them which brand of parachute is better though. And only tell them to grab a parachute after you’ve made sure that they value their life in a somewhat similar way as you do. Otherwise you may be accused of advocacy.


In the end, we’re damned if we do and damned if we don’t use scientific lingo and qualifications/weasel words/passive voice that are the norm in scientific discourse. If we do, the message will get lost on or misinterpreted by the public. If we don’t, we’ll be accused of hiding uncertainty/adhering to dogma/being an advocate or whatever accusation happens to be in vogue. I wrote about this catch 22 before.

It will continue to be a balancing act to be both true to the science and make the message palatable and interesting to the audience. But one thing is for sure: Talk the same way as you do to your fellow scientists and your message will fall on deaf ears. Check out Steve Schneiderand Randy Olson for some very useful perspectives on this balancing act.


Mooney again:

You’re going to be accused of being an advocate no matter what you do. (…) Don’t get angry, and don’t get distracted. Remember what it is that the (…) public, and political leaders, need to know about climate research–and tell them that. Tell them twenty times. And then do it again.

Don’t let your anger or frustration shine through in your communication. It doesn’t go over well (except with people who share your anger or frustration, which seems to be a major factor for blog popularity).

The risk of postponing corrective action to a gradually deteriorating situation

July 21, 2010

At the drug store there is a short information video about the health risks of smoking, featuring the following:

Smoker: “Nothing is bothering me at the moment.” (NL: “Ik heb nu nergens last van.”)

Medical advice: “It is dangerous to postpone quitting smoking. Not all consequences are reversible at that point.” (NL: “Wachten met stoppen is gevaarlijk. Niet alle gevolgen zijn dan nog terug te draaien.”)

The same can be said about climate change. Nothing about the future is for sure, but different actions bear different risks. Postponing any meaningful mitigation action until the shit hits the fan comes with considerable risk, because many changes in climate are not reversible on human timescales. Once you notice the trouble, it’s only the beginning, because of the inertia in the various systems (energy-, carbon cycle- and climate system). The ‘stop’ button has a delay of multiple decades, which means you have to act based on foresight, or what comes closest to it (e.g. projections based on science).

Steve Schneider, who sadly just passed away, said about a potential treatment to his disease:

I was willing to take the low risk of using the drug in order to avoid the high risk of the can­cer count building up and being hard to reverse.

Climate and health: Both are a matter of risk.

If the situation deteriorates only gradually, rather than shock-wise, it is apparently much harder for people to seriously gauge the risk. It’s tempting to say: “Oh, I can still bear this”. It’s as if your point of reference gradually moves in synch with the situation. In such cases, a helicopter view is especially important.

Reflections on climate discussions in the blogosphere between Keith, Lucia and me: The spectrum of opinions, uncertainty, risk and inertia

June 11, 2010

Keith Kloor has a post up that is an almost literal transcription of a conversation we had between him, myself and Lucia.

It’s a good initiative I find, to attempt to ‘bridge the climate divide’, as his post is titled. It’s an important theme for me as well. I’ve tried to find common ground with others before, e.g. Tom Fuller and Roger Pielke Jr.  Not that I see such a huge divide between Lucia and myself at all, but that’s also what makes such a conversation both possible, useful and enjoyable. A conversation between more extreme or more excitable voices on either side may quickly become an exercise in mudslinging; there has to be some common ground in order to have a conversation.

The crux of what I had to say is this (quoting myself):

So you have a large amount of inertia in the energy system, in the carbon cycle and in the climate system, which means if you start taking actions, it’s decades into the future until they start taking effect.

If you combine that inertia in those different systems, with uncertainty of the precise effect, and with some knowledge that it could go pretty wrong with a business as usual scenario, then you have to take proactive steps, and that’s where the urgency comes from.

In my view, it’s similar to a chainsmoker who gets told by a physician, “hey, you should really be careful, you should stop smoking if you care about your heath.” And the person says, “hey I can still bike to the town and I feel fine and my grandmother lived until she was 96 and died in a car accident.”

You can postpone dealing with smoking until you’re in the intensive care unit. But that’s a little late. That’s the line of argument in which I see the urgency of climate global warming.

I plan to go into these issues in more detail at some point.

Thanks Keith and Lucia!

Lucia’s report is here. She makes the interesting observation that

It seemed that Bart and I may disagree less when on Skype than when posting comments at Roger Pielke Jr.’s blog. That’s an interesting thing in and off itself.

Though perhaps we have slightly different recollections of our (few) discussions at Roger’s. We never were very antagonistic as far I recall, though on the impersonal internet it’s always easier (tempting even?) to be more antagonistic than one is in “real” life (insofar as Skype is real and not internet; ah well, you get the point).

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