New paper: Can we trust climate models?

Our latest paper, Can we trust climate models? has just appeared on the Wiley website (open access thanks to our Japanese friends who paid for this). To save a click, here’s the abstract:

What are the predictions of climate models, should we believe them, and are they falsifiable? Probably the most iconic and influential result arising from climate models is the prediction that, dependent on the rate of increase of CO2 emissions, global and annual mean temperature will rise by around 2–4°C over the 21st century. We argue that this result is indeed credible, as are the supplementary predictions that the land will on average warm by around 50% more than the oceans, high latitudes more than the tropics, and that the hydrological cycle will generally intensify. Beyond these and similar broad statements, however, we presently find little evidence of trustworthy predictions at fine spatial scale and annual to decadal timescale from climate models.

The paper was invited by the editors some time ago, under a slightly different title but they didn’t object to us changing this to something that we felt matched the content a little better. The original plan was for two papers to appear together, with the other one written by a prominent sceptic. However, this seems to have fallen by the wayside. Although we could probably have guessed what they were likely to write, we didn’t really want to take part in a direct debate, so rather than aguing against straw man criticisms we just tried to set out our own ideas. Given how it turned out I’m glad we did this! I don’t think our argument is likely to be considered controversial – perhaps some might think we are a little pessimistic about the regional performance of models (by which we basically mean anything less than hemispheric) but our recent work with paleoclimate really has brought home to us that they don’t get much right about patterns on this sort of scale, even for temperature still less precipitation.

The reviewers made some helpful comments, perhaps the only real criticism was that we sounded like a bland consensus and weren’t really making an opinionated statement as might be hoped for in an “opinion” article. But we wanted to say what we thought was correct and justified (ie, a true summary of our opinions), rather than being artificially controversial. I’ll be very happy if the paper is seen as a useful summary of how much we can trust climate models, and why.

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5 thoughts on “New paper: Can we trust climate models?

  1. Hi J&J,
    The message in this paper seems simple enough, but I imagine it is both unpopular and more important than some non-scientific types might think. Having worked in the area for several years, it is clear that there are plenty of sensible efforts at a local and regional scale to constrain the worst impacts of a changing climate. In the UK, most of these depend on the output of the regional models used in CIP09. Efforts in Africa and other vulnerable regions focus on similar RCMs and heavily on Met Office and US (NASA/NOAA, etc) output.
    On top of this, a great many of the research papers with a regional or local focus make use of the modelling available to attempt future scenario forecasts. Then there are the various specialist NGOs and analytics people who work in insurance, banking, security and policy. In sum, the majority of actual work and good intentions on mitigation and adaptation base their ground zero on the assumption that climate models have skill at the sub-hemispheric scale.
    The implications of your findings are therefore substantial: it is possible that a great deal of effort is being misdirected, or the risks misunderstood. My feeling is that this needs more public and detailed understanding.
    On the other side, not every piece of news is bad. In this paper, the MET scientists involved suggest that skill is possible at certain things on certain scales (your feedback on the paper appreciated, if you have the time): http://www.hydrol-earth-syst-sci.net/18/2669/2014/hess-18-2669-2014.html
    It’s a bit of a double bind: we want to see something being done, but at the same time, we don’t want to see the wrong things done for the right reasons, in the absence of better knowledge…

  2. Hi Fergus,

    Thanks for the comment. Thanks to the venue, I suspect it will attract relatively little attention – WIRES seems to be struggling to get noticed. As for the HESS paper, we didn’t consider time scales as short as monthly/seasonal, but I’d agree there is certainly some useful skill there in some situations.

  3. The other worry about your paper is more about the impact – any implied criticism of modelling feeds the piranhas, who then regurgitate lies in an attempt to discredit science. I know some people who see you as a conservative voice in the larger climate debate, because you refuse to subscribe to the more melodramatic outpourings of the less well-informed.

    Back to the point, though, is there a way forward to improve the skill of models at a regional level? Given that the data which feed the initial conditions of models operates on defined scales, increasing the scale of the derived results is unlikely to be productive. Does this mean that, for the foreseeable future, we have to be content with levels of confidence which are low, but slowly increased by reanalysis as new data becomes available, or is it feasible to start a new RCM program with different scales of initial conditions and derive intrinsically more reliable results? Or is this constrained by what we already have available?

    Any suggestions on how to improve the situation?

  4. Well, there is always “improve the models” but that strategy seems unlikely to bring rapid results. There are also some interesting ideas relating to reanalysing the output of the models that already exists (ie correcting the biases), but that’s very much work in progress AIUI.

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