Climate change risks

I thought I would briefly mention a paper, by Simon Sharpe, that is currently under review and that discusses how we should present climate risks. It was highlighted by Steve Forden on Twitter and suggests that climate risks should be plotted as probability over time. The suggestion is that what we mostly see are impacts (such as global surface temperature) plotted against time. The paper argues that

a more appropriate means of assessing and communicating the risks of climate change would be to produce assessments of the likelihood of crossing non-arbitrary thresholds of impact, as a function of time

Credit: Schellnhuber et al. (2016)

The ideas, as I understand it, is to consider some thresholds beyond which we might expect some impacts to materialise. We can then present the probability of us crossing these thresholds and how this probability will change with time under various scenarios.

For example, as the figure on the right illustrates, if we cross 2oC we have a high chance of losing coral reefs, and a reasonable chance of losing Apline glaciers and summer Arctic sea ice. If we warm further, then other outcomes become possible, and become increasing likely if we continue to warm. If we could quantify the probability of these various outcomes, and how this changes with time, then we could inform what we would need to do if we wanted a good chance of avoiding some, or all, of these outcomes. Similarly, we could highlight at what point some of these outcomes become very likely if we do not take action to avoid them materialising.

Although I do think it is useful to consider things in this way, I can see some complications. The probability of various outcomes depends largely on the emission pathway we actually follow. Although we have some control over future emission pathways, it’s not straightforward to determine the actual probability of actually following one. Hence, it’s not clear how we can really quantify the likelihood of crossing non-arbitrary thresholds.

We could, of course, present conditional probabilities (i.e., how the probability of crossing some threshold varies with time given some emission pathway) but this suggests that this framing isn’t quite as straightforward as it may seem. I do still think, though, that this is a reasonable way to consider this. It may be that there is some straightforward way to present this, but I suspect that this is a topic about which nothing is ever quite straightforward.

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18 Responses to Climate change risks

  1. John Hartz says:

    ATTP: By happenstance, I came across the following article today. What it describes and illustrates in graphic form is another dimension of what you have addressed in your OP.

    Visualizing Interconnections Among Climate Risks, Mindzilla, Feb 28, 2019

  2. Further to your point that it is unclear that “time” is what we should be measuring ‘probability of impact” against… I am not even sure that we should be measuring it against “emission pathway” as against “cumulative emissions” (*). Which, you could further then turn back into time by saying that you will cross threshold X of cumulative emissions (and probability Y of impact Z) within W years on the current emission pathway.

    Which is pretty hard keeping track of, but I think you need cumulative emissions or a carbon budget in there. (* and, of course negative emissions has made the whole carbon budget framework far more problematic, but presumably you still hit a peak in the cumulative carbon emissions…)

    By the way, the risk/impact I would be most concerned would be the one(s) described last year in “Trajectories of the Earth System in the Anthropocene”/, which – as you would know – considers the disturbing possibility that there is no stable climate around 2C… That there may be attractors in Earth system dynamics that initiate and reinforce warming and carbon feedbacks so that the system moves to discrete stability points far outside the Holocene of Holecene ~+2C,,, That, to me, is a risk/impact that we should be communicating and working to avoid above all others…

    Trying to make that a bit more lucid: I am more concerned about a (the) cascade of reinforcing impacts than I am in considering them one by one…

  3. Everett F Sargent says:

    Stuff like this …

    “or the height of sea level at which it becomes less costly to relocate a coastal city than to continue to protect it against flooding”

    “the impact of a past event whose damage is well understood, e.g. a storm surge equal to that of
    Superstorm Sandy”

    There are places where this is completely covered from a risk standpoint and they ain’t in the UK!

    We all got more than our fair share of sand dunes and barrier islands and tropical and extratropical storms. Not even sad, just plain pathetic. :/

  4. KiwiGriff. says:

    For example, as the figure on the right illustrates, if we cross 2oC we have a high chance of losing coral reefs, and a reasonable chance of losing Apline glaciers and summer Arctic sea ice.

    Yes it all sounds so unthreatening.

    Coral reef ecology is part of the life cycle of many commercial fish species that we will lose. We also lose the coastline protection and land building generated by coral reefs over time.
    Alpine glaciers supply consistent running water that irrigates land over large areas so we may lose agricultural productivity and water security over huge regions. Summer sea ice has a significant effect on global weather as we see with the meandering jet stream “Polar vortex” weather pattern that seems to be emerging.

    We are talking about simultaneous effects that dont just add they multiple the risk of significant impacts.

    Lose 10% of fisheries due to coral die off another 10 % from loss of productivity due to losing the moderating effects on stream flows from glacial melt and 10% from inconsistent seasonal weather patterns effecting agriculture and you are looking at the possibility of 30% of global food supply lost. Even if such effects coincide only once every few years …. when it does Global catastrophic food crisis’s resulting in wars and famine .

    We are loading the dice far in excess of the individual risks taken in isolation .

  5. Kiwi,
    Sure, I wasn’t suggesting that there aren’t even more severe impacts that we should be highlighting. I also agree that the issue of multiple impacts coinciding is something to consider.

  6. Steven Mosher says:

    Even though I like this chart ATTP, I’d like to see a follow up.

    A storyline for every one of those tipping point stand pipes. so 5 stories and all the related
    impacts over time.

    I’d wager within those tippiong point stories lines you’d have one that was closest in time, that was highest probability and most impactful ( connected to other things)

    As for scenarios, for rhetorical effect, I’d do a projection where every country started to follow the percentage of cuts in emissions that the UK has. Just to put it in a framework of what is proven to be achievable.. we have abstract scenarios ( 2.6, 8.5 etc) but it would be a good rhetorical effect to say ‘Assume every nation cut there emissions as the UK has over the last x years)

  7. Steven,
    Yes, that all sounds quite reasonable. You would then run into the standard problem of it becoming rather complicated and it being more difficult to present something that could have some kind of impact on those who don’t have the time, or inclination, to delve into all of the details. Some of what you describe already exists in things like the IPCC reports.

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  9. John Hartz says:

    Speaking of risks…

    A Nearly $1 Trillion California Flood Likely to Occur Within 40 Years by Jeff Masters, Category 6, Weather Underground, Mar 4, 2019

    The $1 Trillion Storm: How a Single Hurricane Could Rupture the World Economy by Geoff Dembicki, Vice, Mar 3, 2019

  10. Steven Mosher says:

    Ya ATTP.

    My sense is such a presentation would not be for everyone.
    but once you have the complete storyline its easy for story tellers to shorten the plot,
    pick the main characters, and still hew to the truth

  11. Joshua says:

    Mark –

    Hard to pick an old thread to post on that might be relevant, so I picked this one since it didn’t garner much attention originally:

    I don’t recall having heard that righties are more tribal than lefties, although the reasoning sounded OK at a quick listen at least superficially.

    I’m a pretty dedicated symmetricist, but to maintain that view it seems I have to dismiss more and more reported evidence of asymmetry. My main caveat, still, is that even if the evidence of symmetries can be validated, it still doesn’t justify an argument that the differences are really important – IOW, I need to see evidence that the differences across groups is significantly predictive when we consider that there is also variation within groups.

    If it’s true that we Righties are more tribal than you darn Lefties,

    I’ll have to listen again, but that wasn’t a take away for me. However, I do think that whether because of fundamental psychological differences, or cognitive differences (and I think it isn’t), I do think there is a certain structural imbalance. Yes, I think it’s probably true that in general righties are somewhat more status quo oriented and that maintaining traditional social structures is more important to them*. In that sense, the signal of tribalism is more fractured and varied among lefties, and so in a sense harder to recognize because their tribalism, while just as prevalent and just as strong, takes a wider variety shapes. That goes along with the demographic patterns where righties are more unified along a more or less single, “nationalistic” vector; whereas lefties are unified along a series of vectors.

    Mostly, I have read a few comments from you over at Lucia’s about race, and was curious as to how you’d incorporate/reconcile the info from that pod with those views about race that I’ve read you express.

    An unimportant aside – I always feel as though if I only took enough of some psychedelic mind altering drug for a long enough period of time, I’d be able to understand where Ezra Klein is coming from.

    Which aspects of where he’s coming from seem so far from your view of the world?

    * Which is largely, to be expected, because righties are more or less unified along certain groupings which have, traditionally, placed them at an advantage. Thus, it only stands to reason that they’d want to maintain that traditional status. Accordingly, I don’t think you (necessarily) need to go into psychological or cognitive characteristics to explain why they’d be status quo (tradition) oriented, and that’s why I’m skeptical of evidence that their status orientation is some inherent attribute. Another problem I have with the putative evidence of inherent differences between lefties and righties is that I have yet to see a particularly plausible causal mechanism to explain that. Seems to me that people are (more or less) oriented in certain directions as a function of their culture of origin – people go along, ore or less, with the traditions of their identity groups. How would the explanation that inherent cognitive or psychological differences develop in people to drive them to certain groupings explain the overwhelming signal of culture of origin? Hopefully that argument makes some sense (I’m trying to explain my thoughts without making the comment eve more ridiculously long).

  12. Mark Bofill says:


    Just in time. I was trying to put together an opening comment on the thread you originally linked this on talking with Izen.
    The business about righties being more tribal wasn’t any sort of key takeaway for me either (although unless I had crud in my ears I’m pretty sure it was put forward – not impossible, my hearing isn’t the best); more of a joke and a segue to move the conversation over so people would stop taking random pot shots at you.
    Ugh. Interruptions. I gotta take my kids and feed them someplace. They’re complaining something along the lines of not eating all day… These aren’t little kids.. teenagers who didn’t take the trouble to make themselves lunch…
    I’ll be back. It was hard for me to walk away with one idea from the podcast, they wandered around alot, but at least a few points seemed interesting to me.
    Thanks Joshua.

  13. Joshua says:

    Take your time. Kids are people too.

  14. Mark Bofill says:

    I’ll respond to your remarks first:
    Regarding symmetry, I don’t know. The two groups might not be AFAICT. It would be nice (more convenient from my perspective) if they were.
    Mostly, I have read a few comments from you over at Lucia’s about race, and was curious as to how you’d incorporate/reconcile the info from that pod with those views about race that I’ve read you express.
    Help me out – which comments are you referring to?
    Which aspects of where he’s coming from seem so far from your view of the world?
    Little things include his choice of words. I think I remember him talking in the podcast early on about people caring about politics for different reasons (the few who do) – he said something like he was radicalized by the health care issue. At least it’s what I heard him say, and it stuck in my mind as a darn odd way to put it. It’s a small thing in and of itself; to care about politics is to be a radical in some sense? Sure I guess, – in the sense that most people don’t really care. Obviously though there are other associations, other meanings to the word.
    A much weirder thing from my perspective was that he talked about his view being pragmatic (not the word he used, something like that though. Policy oriented maybe, that wasn’t it exactly either. Something along those lines) whereas some others approach politics from a philosophical perspective; first principles and such. That wasn’t the weird part, here it is – then he goes on to .. what, dismiss, maybe? say dismiss this approach by saying he doesn’t care about the tradition or lineage of the ideas. Good Ness. In my view there’s a lot more significance to a philosophy based approach than just historical detail such as what school of thought, group and philosopher! I thought it was the strangest thing for him to say.
    Normally when I think somebody has said something that strange, it turns out that they actually have said nothing remotely resembling what I understood them to be saying, I’m aware of this. I haven’t had time to go back over it yet, but it’s on my list. The fact is, I’m a much better reader than I am listener. I don’t listen nearly as well as I’d like to.
    There were other things, maybe I’ll make better note of them when I swing back through.
    Regarding the stuff in asterisks – so do you not buy the idea that there is a meaningful correlation between big five openness and contentiousness and political leaning? I’ve heard the claim but I’ve examined none of the data or methods. I was prepared to accept it at face value, lacking some specific reason to go look into it. Or do you think the correlation is legit but explicable in some other way.
    Regarding the podcast – there were things that set my teeth on edge. No point in going through a laundry list of irritations. The stuff I liked — the notion that there is an ideal balance between the welfare state and capitalism that keeps society running optimally sounded like truth to me. The idea that people are more willing to tolerate the disruptions/ displacements market innovation brings with a generous social safety net (Wilkinson said this better but something like this). I also liked it because I agree that market games look like they ought to tilt over when they run long enough like a game of monopoly. Probably it’s not stable, and if it’s not stable it’s not in *anybody’s* interest to let it topple over.
    I was with Wilkinson on the problem of elite’s ‘trapping’ of the state’s regulatory bureaucracy, although Klein seemed to disagree. More regulatory power doesn’t solve the situation; the elite or elite organization (whatever) games the complicated system (or corrupts it) and wins regardless. I didn’t see where Wilkinson was going with this unfortunately; it would have been interesting if he had some solution beyond something to the effect of – *well we have to try to balance it* or something like that. Again, maybe I just didn’t absorb his meaning if he did put forward a solution there, I’ll listen again.
    This comment is rambling on forever, I’ll stick some ending punctuation in and post this.

  15. Mark Bofill says:

    I’ve been thinking it over, and I can’t see where your going with race on this. I looked at the polling data you posted hoping it’d be a clue, but it hasn’t helped. My takeaways from the podcast with respect to race were pretty minimal in fact. I got that minorities are overwhelming Democrat. I got the point that personality distributions *aren’t* different for different ethnicities (obviously), so a consequence of minorities being overwhelmingly Democrats is that the Democrats have to encompass a wider range / greater diversity of personality type. (Now, I will say meh quietly here, but I’m reviewing what I heard said, not my evaluation of the quality or merit). I got the claim that Republicans are a much more homogeneous group, generally speaking, and that they really don’t have to accommodate the same range of personality difference that the Dems do. I got (I think) the argument as to why population centers (cities and such) are more liberal and are home to a greater percentage of minorities.
    I didn’t actually listen all the way to the end, maybe I missed something important. But I’m not sure what you make of all this.

  16. mark bofill says:

    Say Joshua, there’s no particular need to impose on Anders or on Lucia. Here:
    I’ll answer you here or whereever (until somebody asks me to quit it, I guess), but I’m going to post more my verbose trivia at that link. You’re invited to do the same.
    (I forgot I even *had* a wordpress account til I posted here again. Heh)

  17. Joshua says:

    Hey Mark –

    I’ll respond over there.

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