Attribution

There was a truly awful article in the Telegraph a few days ago called what if man-made climate change is all in the mind. It was written by a novelist called Sean Thomas, so my initial thought was that he was practicing his fiction writing. If so, it was quite good (well, in the sense that it was very obviously fictional).

The article itself was discussing the recent flooding in England and quite heavily quoted Corinne Le Quere, a Director of The Tyndall Centre for Climate Change Research. Corinne Le Quere was quoted as saying

“Even though we can’t blame the current weather in the UK on climate change, we expect heavy rains like this to occur as a result of climate change”.

Seems quite sensible to me. The article rather mocked what Corinne Le Quere was saying, with the the basic premise that there is no evidence for increased precipitation and hence maybe

man-made climate change is all in the mind – because, in our instinctive terrors, we always think that something wicked this way comes, especially from the sky: as a punishment from God, for things we have done.

Corinne Le Quere responded with an article of her own in the Telegraph called what if man-made climate change is loading the dice on floods in the UK. The article ends with

If Mr Thomas would like to improve upon his fictional writing, my university, the University of East Anglia, has an esteemed creative writing programme, though he’ll have to do better than this to win a place.

So, maybe, even as a piece of fiction it wasn’t very good.

You can read the articles yourselves to make up your mind about their relative merits, but what I thought I would do here is quickly address the issue of attribution. It seems that we’re confident that we can attribute recent surface warming to human influences. I assume that we can also attribute the rise in ocean heat content, the reduction in Arctic sea ice, and the loss of ice sheet mass in the Antarctic and Greenland to human influences. However, when it comes to extreme weather, it’s much more difficult to determine attribution.

So, what seems quite common is that if anyone attempts to associate an extreme weather event with climate change/global warming someone will pop up and say either “there’s no trend”, or “the trend is not statistically significant”, or “the trend is statistically significant, but we can’t attribute it to human influences”. All of these statements may be true, but they’re often simplistic. Even in the case of the recent flooding, Corinne Le Quere very specifically said that we can’t blame the recent weather on climate change. What she was saying was that science is telling us that climate change will very likely lead to more heavy precipitation in the UK.

So, as I see it, we’re confident that the warming is anthropogenic. We’re confident that sea levels will rise (basic physics). We’re confident that wetter regions will get wetter and that drier regions will get drier (basic physics). We’re, however, uncertain about precisely how some extreme weather events will be influenced by climate change. Also, in most cases we won’t be able to determine attribution for many decades, even if there are some hints today.

It certainly appears that these attempts to argue that we can’t definitely attribute extreme weather events today to man-made climate change are simplistically true and would seem to simply be delay tactics. Surely one reason for doing science is to use our knowledge of physics, chemistry and biology to understand how things may change and to make decisions as to what to do to avoid future problems? Implying that we shouldn’t do anything until we know definitively that there is a genuine problem, seems rather medieval. If this is your thinking, then what’s the point of doing science (as I understand it at least). Just wait until it’s obvious that there’s a problem and then do something about it. I think that’s rather short-sighted, but maybe I’m alone in this.

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32 Responses to Attribution

  1. Rachel says:

    Corinne Le Quere’s article was really good. I think I might have followed one of your tweets to it.

    It is one thing to say that we cannot attribute climate change to one particular weather event and another to say that there is no link at all between climate change and extreme weather events. It’s my understanding that scientists are predicting more extreme weather events and just because we don’t yet have enough data to prove that this is the case, does not mean that it is not true.

    The manner with which this is presented by contrarians reminds me of big tobacco and how they tried to push the cigarettes are not harmful myth by way of lack of evidence.

    But what is truly strange to me is why are we not preparing for this risk? We take out insurance for all sorts of things that are very unlikely to happen to us – like our house burning down – and yet things like floods are far more damaging and to far more and we are not doing anything to mitigate this risk.

  2. Yes, it seems to fall into the “absence of evidence doesn’t mean the evidence of absence” type of issue. It does seem as though many get very excited if anyone associates an extreme weather event with CC/GW, even if they’re careful about how they do so. However, they have no problem with people saying “global warming did not cause ….” despite them claiming that we can’t make statements like “global warming has caused ….”.

  3. johnrussell40 says:

    Sean Thomas must be very smug thinking he is much superior to the world’s scientists who are, of course, all susceptible to ‘chicken little’ superstitions. It hasn’t occurred to him that maybe primitive defence mechanisms hard-wired into his brain are producing his denial and without science he can’t see his way beyond them.

    Regarding attribution. I’ve always liked the analogy that ‘global warming widens the goals and shrinks the pitch’*. So it doesn’t directly participate in the game and it can’t score the goals. It does however make it easier for the players (weather) to score goals. But, turning that round, given an increase of—say—50% in the number of goals per game, can we say any particular goal was scored as a result of the modified pitch? No chance. And it’s the same with climate change: it modifies the atmosphere in which weather plays out its events, but it will always be the weather which creates the events. It’s unlikely that extreme weather will ever be linked to AGW in any other way than by statistics.

    *The American equivalent of this analogy is ‘raising the floor of the basketball court’.

  4. izen says:

    Some events like increased rainfall and more powerful storms can only be definitively attributed to climate change after sufficient events to establish a statistically significant trend. That there may not be enough event data to make that attribution of significance yet is not evidence that the attribution is wrong. To steal Judith Curry’s uncertainty monster, the present uncertainty is entirely symmetrical, it neither refutes the attribution of events to climate change or validates the attribution.

    The prediction from the physics that warming will increase rainfall because of increased water vapor is a credible prediction. The increase in water vapor is a measured fact, the increased rainfall is not so easy to verify.

    I like the analogy or metaphor that we are living in a ‘Lance Armstrong’ climate. While no particular win/extreme event can be directly attributed to the steroid intake, the overall pattern of events is certainly attributable to the drug use. It has the added strength of encompassing the strenuous and repeated denial of the fact long after the role of performance enhancing substances was established!

  5. John,

    It’s unlikely that extreme weather will ever be linked to AGW in any other way than by statistics.

    In an attribution sense, I suspect you’re right. If it wasn’t for the contentious nature of this debate though, I suspect most would be happy with a theoretical/model prediction that appeared to match reality without needing to then do the analysis that formally attributes the changes in a particular type of weather event to anthropogenic influences. So, showing that one can attribute it to human causes if powerful if it can be done, but given that it mostly can’t (for a long time at least) provides an extra element of uncertainty to be used by those who wish to portray things as uncertain.

    Izen,
    Thanks. I agree about the uncertainty issue being symmetrical. The way some present it though makes it appear as though a lack of attribution is equivalent to “global warming did not cause …”.

  6. I would be surprised if there were no attribution studies on precipitation yet. For observed trends in heavy precipitation there are many studies. In Europe winter extreme precipitation shows increasing trends (Moberg et al., 2006; Kysely, 2009), although not everywhere (Toreti et al., 2010). Maraun et al., 2008 found increases in heavy precipitation in the UK. In summer no clear pattern in the trend of precipitation extremes can be found (Costa and Soares, 2009; Kysely, 2009; Maraun et al., 2008; Moberg et al., 2006). Globally the IPCC-SREX states that it is likely that there have been statistically significant increases in the number of heavy precipitation events (e.g., the 95th percentile) in more regions than there have been statistically significant decreases, but there are strong regional and sub-regional variations in trends (IPCC, 2012).

    Costa, A.C. and A. Soares, 2009: Trends in extreme precipitation indices derived from a daily rainfall database for the South of Portugal. Int. J. Climatol., 29, pp.: 1956-1975.

    IPCC, 2012: Managing the risks of extreme events and disasters to advance climate change adaptation. A special report of Working Groups I and II of the Intergovernmental Panel on Climate Change [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, UK, and New York, NY, USA, 582 pp.

    Kysely, J., 2009. Trends in heavy precipitation in the Czech Republic over 1961-2005. Int. J. Climatol., 29, no.12, pp. 1745-1758.

    Moberg, A., P.D. Jones, D. Lister, A. Walther, M. Brunet, J. Jacobeit, L.V. Alexander, P.M. Della-Marta, J. Luterbacher, et al., 2006: Indices for daily temperature and precipitation extremes in Europe analyzed for the period 1901-2000. J. Geophys. Res. Atmos., 111, no. D22.

    Maraun, D., Osborn, T.J. and Gillett, N.P., 2008: United Kingdom daily precipitation intensity: improved early data, error estimates and an update from 2000 to 2006. Int. J. Climatol., 28, pp. 833-842.

    Toreti A., F.G. Kuglitsch, E., Xoplaki, J. Luterbacher, H. Wanner, 2010: A Novel Method for the Daily Temperature Series and Its Relevance for Climate Change Analysis. J. Clim., 23, pp. 5325-5331, doi: 10.1175/2010JCLI3499.1.

  7. Victor,

    I would be surprised if there were no attribution studies on precipitation yet. For observed trends in heavy precipitation there are many studies.

    Yes, there may well be and that would be my lack of knowledge showing through. Having said that – for some – showing human influences in increased precipitation would still not be enough to indicate human influences in increased flooding.

  8. OPatrick says:

    Having said that – for some – showing human influences in increased precipitation would still not be enough to indicate human influences in increased flooding.

    Or they will point to every conceivable human influence other than increased precipitation. As with most problems we face from climate change there is always another more proximate cause – building on flood planes, changes in land use etc. – so the contribution from anthropogenic climate change can safely be dismissed.

  9. OPatrick says:

    Totally off topic but worth a quick giggle – tallbloke’s reply to one of William Connolley’s comments at his blog on the Pattern Recognition in Physics axing:

    Let our scientific work stand on its merit, rather than impugning the honesty of the scientists.

  10. OPatrick,
    Yes, they’re fantastic. I was thinking of writing a post about this, but I’ve had a couple of glasses of wine, so thought a bit of discrection may be in order. Tomorrow, maybe 🙂

  11. Rachel says:

    I’m not familiar with all the climateball characters. Can someone please explain who tallbloke is and what he’s got to do with the axing of that journal? Did he have some papers published in it? He doesn’t appear to be a scientist.

  12. Already inviting Tallbloke to be an editor would be sufficient reason to loose confidence in the editorial board and close a new journal down before it hurts the reputation of the publisher beyond repair. That was the joke of the year! 🙂 I would almost say, they wanted to be closed down, so that they could protest about being suppressed and play climate martyr. After hearing that little fact, I can only say: Well done Copernicus!!

    I had not read the article in the Telegraph, Three headed baby aborted by aliens, and had not realised that the issue was the sophistry about attribution of flooding directly. Clearly everything else being equal more (heavy) precipitation increases the flood risk. Sure climate change is just one stressor, but are there people expecting less floods from more and heavier precipitation?

    A formal attribution study for floods will be nearly impossible. You need to work on a large scale to get statistically significant results and at the same moment you would need to know all the local changes (building in flood plains, but also improved zoning, higher and stronger dykes, dams, water retention basins, re-naturation and canalisation of rivers, polders to be flooded in emergencies, etc.) for this entire region.

  13. Rachel, Retraction Watch wrote: “Journal guest editor Roger Tattersall — known as Rog Tallbloke online ”

    My last comment is (again) in moderation. Sorry for making you guys so much work.

  14. Rachel,
    I believe that Roger Tallbloke is actually Roger Tattersall, who writes a blog called Tallbloke’s Talkshop but was also one of the editors of the special issue of Pattern Recognition in Physics that was subsequently axed by the publisher. He seems to regard himself as an expert on the solar system and climate science. There appears to be no evidence that this is true. Maybe you remember this, but he is also the person who initiated the suggestion that my new name should be UF.

  15. Victor, this time it wasn’t you. Tallbloke is an automatic moderation term 🙂

  16. Rachel says:

    Thank you, both of you. Yes, I remember the UF now.

  17. BBD says:

    Just look at the names that come up in PRiP:

    Scafetta, N.-A. Mörner, Willie Soon, Archibald, Easterbrook, R. Tattersall.

    No more OT from me, but interesting, isn’t it?

  18. BBD says:

    Sorry, I lied.

    This from Scafetta at RT’s blog:

    This is a very sad story. This is the only way people like Connolley and company can think to win a scientific debate.

    Now that really is it. Apologies.

  19. Rachel says:

    I’m not going to delete OT, especially since I’m dying to post this tweet:

  20. BBD says:

    Schadenfreude is us 🙂

  21. Rachel says:

    I know, aren’t we awful.

  22. BBD says:

    Kevin Trenberth’s statement on attribution bears repeating:

    The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be….

    The air is on average warmer and moister than it was prior to about 1970 and in turn has likely led to a 5–10 % effect on precipitation and storms that is greatly amplified in extremes. The warm moist air is readily advected onto land and caught up in weather systems as part of the hydrological cycle, where it contributes to more intense precipitation events that are widely observed to be occurring.

    More here.

  23. I’ve never liked the desire to pin extreme weather on GW. My personal take on this is: if you want to know if “GW is true” then the obvious thing to do is look at the global temperature. Its a nice statistically stable well understood measure which is intensively studied (RP Sr pushes ocean heat, the problem is its poorly observed not-long-ago). Unfortunately, its not very exciting. It creeps up by tenths of degrees. It is not charismatic megafauna. So people inevitably seek something more exciting, and what could be more exciting than extreme weather? But alas extreme events by their nature have an unstable statistical distribution – by which I mean, if you’re trying to estimate the distribution from observations, and worse trying to estimate changes in that distribution, then you have at best a very difficult task.

  24. I see no problem with studying extreme events. They will likely cause a large part of the costs of not adapting or determine the costs of the adaptation measures. Such studies are hard and it will take many more years before we have robust answers, but it is a legitimate topic.

    Whether you need separate attribution studies for extreme events is another question. There I agree with WMC and it should be sufficient to show that a specific kind of extreme is linked to global warming, as we already have attributed global warming to human action.

  25. BBD says:

    WMC

    Damned if we do; damned if we don’t. Trenberth is, I think, correct, but we are still (just) in the signal vs noise stage, which as you say makes attribution very hard and so risky in pubic discourse.

  26. > I see no problem with studying extreme events.

    Indeed – I’m sorry if I appeared to be saying otherwise (in some kind of hand-wavy sense I think life tends to evolve itself to live up to extremes; of drought, say. So (putting aside for a moment the intrinsic interest of extremes) an “extreme” event that pushes just over a former boundary could have consequences far larger than its absolute deviation from a previous extreme might suggest. However, (a) that’s bio, which I don’t really do and (b) that doesn’t make its statistics any easier). What I was trying to say is that they aren’t very good for attribution purposes. If your aim is attribution, then use global temperature. If you really want to try to attribute extremes, then be prepared for a hard job.

  27. Tom Curtis says:

    “in some kind of hand-wavy sense I think life tends to evolve itself to live up to extremes; of drought, say”

    Only in the very limited sense that it adapts towards the most efficient strategy of recolonization of an area between maximizing a surviving population effected by an event, and maximizing the rate of recolonization from neighbouring, unaffected areas. Clearly for mobile species the later will be the dominant strategy; and for all species maximizing population in normal years is a major contribution to both. The net effect is that species will typically only adapt to extreme events with short return intervals. If the return intervals of extreme events become shorter, then the species will become maladapted to the new climate.

  28. Mircea says:

    Did anyone followed the link to the Financial Times report ? I did and afterward I really felt cheated by Mr. Thomas. Here it is the relevant part from the Financial Times report:

    “We expect storms such as these to become more intense with climate change,” said Professor Piers Forster, a lead author of the landmark report issued in September by the UN’s Intergovernmental Panel on Climate Change.
    “We still can’t predict what parts of the country are going to get these storms,” he said, adding that it was impossible to say whether the gales that flooded homes, cancelled trains and cut power lines were directly caused by climate change. However, he argued, “we can say with some confidence that the severity of storms will increase because of the warming oceans”. Rising sea temperatures lead to more evaporation, adding more moisture to the atmosphere and more energy to weather systems.
    Heavy rains in particular are likely to become more frequent, said another lead author of the September IPCC report, Professor Corinne Le Quere, director of the Tyndall Centre for Climate Change Research at the University of East Anglia. “Even though we can’t blame the current weather in the UK on climate change, we expect heavy rains like this to occur as a result of climate change,” she said. “The UK has to start to adapt to that kind of event.”
    Professor Le Quere added that Britain faced particularly unpredictable conditions because it was close to parts of the world already changing rapidly, such as the Arctic. “The Arctic is melting so fast that it changes the weather patterns in ways that we haven’t experienced,” she said.

    Is there anywhere where prof. Le Quere blames individual weather events on climate change ? No, she says that climate change can/will increase the power and frequency of the rain. The reason why is given a few lines above in the fragment.

    Now, compare this with what Sean Thomas writes:

    Sometimes it’s the silliest statements that tell you the most interesting things. Take, for instance, this Financial Times report into Britain’s latest floods.

    Here are some quotes.
    Professor Corinne Le Quere, director for Climate Change Research at the University of East Anglia [said of the floods], “Even though we can’t blame the current weather in the UK on climate change, we expect heavy rains like this to occur as a result of climate change”.
    What exactly is Professor Le Quere trying to tell us here, with her eerie and echoing syntax? My inner psychotherapist translates it as: “Even though I mustn’t directly blame individual weather events on climate change, I am desperate to do exactly that, because it’s what I believe.” It therefore resembles a statement of faith. Right down to the repeated mantra: like a prayer.“

    He is just inventing. What the heck…

    Mircea

  29. William,

    What I was trying to say is that they aren’t very good for attribution purposes. If your aim is attribution, then use global temperature. If you really want to try to attribute extremes, then be prepared for a hard job.

    I agree, and I agree with your broader point – if you want to know about GW then consider energy imbalance (either surface temperature or ocean). The problem that I see is that people want to know about the consequences. So, scientists then say – for example – “warmer air holds more water, more water means more precipitation, more precipitation probably means more flooding”. So, you have lots of flooding and a scientists says “this is what GW suggests we may see more of in the future” and then someone will pop up and say “ahhh, but we haven’t managed to attribute the flooding to human influences”.

    As I see it, most scientists probably realise that attribution is difficult. Those who are “skeptical”, however, see it as a way of producing an extra level of uncertainty. I don’t have any solution to this because trying to attribute is probably good, but it does – in some sense – give ammunition to those who would rather find reasons not to take GW seriously.

  30. Mircea,
    Indeed. I thought I had got that across in the post, but maybe I should have made it clearer. This seems to be common. Someone says something like “GW will probably make such events more common” and someone else will respond with “you can’t claim GW caused that event”. So, this seems to be one of the Catch-22 issues with trying to attribute. It’s probably not possible yet for many extreme type of events. However, trying and failing then provides some ammunition for those who want to be able to say “you can’t say GW caused …”.

  31. AnOilMan says:

    Anders… if you look at Hurricane Sandy, the city was flooded. It the same Hurricane had occurred 50 years before it would not have flooded. AGW ocean rise most definitely contributed.

  32. johnrussell40 says:

    I think what we should all be saying at every opportunity to friends, colleagues and neighbours, is… “all weather events today and in the foreseeable future are occurring in a world which, thanks to man-made global warming, is on average warmer, wetter and with a higher sea level. With more energy in the system, dry places will be drier, wet places will be wetter and windy places will be windier. What’s more, as our planet’s temperature keeps increasing, so weather events will become more unpredictable and even more extreme. What we’ve experienced is exactly what scientists have predicted will occur. “

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