My ‘next generation questions’ on climate change


Following an interesting conversation I’ve been engaged in with Thomas Fuller (see also the previous post), here is my take on what the next generation questions on climate change are.

Let’s distinguish the following main issues:
– To what extent is climate change occurring, and to what extent is it man-made?
– To what extent is that (going to be) a problem?
– What can or should we do about it?

The first questions are strictly scientific; the middle has a judgment value to it, and the latter is primarily a political/moral judgement (and has more to do with technology than with climate science).

 We have made much more progress in addressing the first question than in addressing the last one. The limiting factor in addressing the issues relating to climate change is not a lack of knowledge about the exact nature of the changes; rather, it is the unwillingness of society to deal with (the consequences of) this knowledge. Even if climate change is less bad than currently expected, we need to dramatically step up our policy response.

I don’t say this to downplay the uncertainties in climate science; there are many, and many of them are large (scientifically speaking). However, within realistic boundaries of the uncertainty, we still don’t do enough to deal with the issue: Any realistic change in our scientific understanding is not going to change the needed policy response, at least not in the short to medium term (~decades). As Herman Daly noted: “If you jump out of an airplane you need a crude parachute more than an accurate altimeter.” And Tom Yulsman: “With a bit of luck, maybe we can agree that regardless of [the details regarding] climate change, we need an Apollo-scale effort to develop transformational energy technologies.” How to shape that effort is the next generation question.

So the ‘next generation questions’ in my view relate to the last one: How are we going to deal with this? There are a lot of tough questions to be answered in that arena, e.g. relating to different technologies (nuclear, biomass, CCS, electric vs hydrogen transport, geoengineering, to name just a few highly contested topics), and relating to more institutional-political matters (e.g. carbon tax vs cap and trade, landuse, changes in consumption patterns, equity issues). Michael Tobis has some excellent writing on the latter topics.

Regarding the ‘next generation of questions’ strictly relating to climate science, some examples of important areas with high uncertainty are the following:
– Regional climate effects
– Climate sensitivity
– The role of aerosol and clouds
– Sea level rise (update: added after Heiko’s suggestion)

However, we need to keep in mind that uncertainty goes both ways, and that science usually progresses with small increments: Three steps forward, two steps back. It is wise to be very skeptical of any claim that the science is radically wrong. Any new piece of evidence just adds to the puzzle; it doesn’t replace existing evidence. Context and perspective are key, and they are often missing in loud proclamations against the consensus.

Let me give an example from an area of research that I’ve been working in for a number of years: Aerosol formation. For at least a decade, sulfuric acid has been regarded a key compound in the formation aerosol particles. The potential contribution of other compounds (ammonia, iodine, ions, organics) has been (and still is) hotly debated, but if someone tries to tell me that sulfuric acid has no noticeable effect on aerosol nucleation, I would not tend to take them very seriously, unless they have extraordinary evidence to back up that (scientifically radical) position. Nothing is impossible, but it’s not very likely.

I think we know a great deal more about the role of CO2 in the climate system than we do about the role of sulfuric acid in aerosol nucleation. I don’t expect a landslide change in scientific thinking on the subject. If someone does, they better bring very strong evidence to the table; a photograph or two won’t do.

(update: the next post elaborates on the major climate science uncertainties)

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10 Responses to “My ‘next generation questions’ on climate change”

  1. Simon D Says:

    That’s the conundrum – more research is necessary, but does not guarantee a reduction in uncertainty.

  2. Bart Says:

    It likely does, though, over the long term. But besides more research, more action is also needed (as in emission reduction). We’re doing much less than current knowledge calls for.

  3. Steve Bloom Says:

    Bart, it seems to me that (transient) sensitivity should never be mentioned in this sort of context without emphasizing what we already know about the equilibrium climate state the last time CO2 was at 560 PPM, and can point to current indicators of WAIS and GIS destabilization as a critical early sign of a transition back to such a state. In a similar vein, one thing we know for sure about aerosols and clouds is that whatever effect they might have is insufficient to block a transition.

    Someone like Fuller is guaranteed to want to misinterpret this stuff, so at least give him links to the recent Pliocene results.

  4. Steve Bloom Says:

    This from Fuller supports my point:

    “The IPCC calculation of 1.5 to 4.5 with a ‘preference’ (help with phrasing?) of 3.5 may be too high. If true, this would greatly reduce the harm expected from a doubling of CO2 concentrations. Does recent research justify a change in the commonly accepted level of sensitivity of the atmosphere?”

    My impression from the Pliocene results is that there’s a fair amount of uncertainty regarding temperature and so also sensitivity, whereas it’s clear that most of the ice was missing. (“How hot?” “Hot enough.”)

    I should add that my example in the previous comment of the ice sheets as early indicators wasn’t meant to be exclusive. The shift of the climate zones, the incipient loss of the non-polar ice, early signs of precipitation shifts (all of these affecting water supply and agriculture), reef damage and loss, and of course ocean acidification all go on the list. Actually it’s a little sad how the denialist talking points Fuller lists sound so quibbly compared to this stuff. (Sadder yet, it looks like at least half of them originate with RP Sr.)

  5. Bart Says:

    Steve, point taken. I meant the standard equilibrium (Charney) climate sensitivity btw, as I make clear now in a follow-up post (in a reply to Tom Fuller’s second post in this saga). I wouldn’t ascribe Tom’s writings to mal-intent however.

  6. Hank Roberts Says:

    Did the Examiner give a link to your blog here so people could find your, er, fuller explanation?

  7. Bart Says:

    Yes, Tom linked to my site. He also posted my entire post at his site (which soon prompted some ‘insightful’ comments of course). It’s good to reach another audience that way, and to see where there may be common ground. Especially the latter is all too often missing.

  8. On Credibility: As Many Walks as Talks | Planet3.0 Says:

    […] Even people who agree on the science and on the needs to address AGW, can disagree vehemently about *how* to address it. That is actually the discussion we should be having in society. […]

  9. The Fallacies of Risk | Planet3.0 Says:

    […] According to Hansson, there is “a fairly general tendency to describe issues of risk as “more scientific” than they really are”. I think he’s right. This is just one of the ways in which politicians try to evade their responsibility for difficult decisions. It could be one of the reasons our society develops towards a technocracy. There is only one cure: emphasizing again and again that both science and politics have their own responsibilities and tasks. […]

  10. ClimateDialogue about climate sensitivity, by Bart Verheggen Says:

    […] Climate sensitivity is a policy relevant metric, since a more sensitive climate would warrant stronger emission reductions in order to remain below the same target of maximum allowable warming. Since global emissions are still rising, this is however merely relevant to future policymaking. Even if ECS is on the low side of the likely range,  emissions would have to be reduced (though less drastically so) in order to remain below the two degree target, for example. Any realistic change in our scientific understanding is not going to make a big difference for the r… […]

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