It the previous entry I wrote about the perils and pitfalls of event attribution. In this entry I want to untangle a few issues and, then, ultimately reframe attribution. Reframe? This is in the spirit of psychology and sociology, a different way to look at something. In this case, take the word, “attribution” and think about the meaning of this word, say, from the point of view of scientists, journalists, politicians ….
To be concrete, start with this scenario.
1) There is an extreme weather event, perhaps a hurricane submerges New Orleans, or a heat wave kills 1000s in Moscow.
2) Advocates say that the event is global warming.
3) Politicians say that the event is global warming.
4) Scientists suggest that the circumstances of the event are consistent with global warming.
5) Journalists ask if the extreme event is natural or global warming.
6) Different groups of scientists hurry to investigate the event. It takes a while.
7) The scientists publish their papers and because the event was newsworthy, the journalists follow up and ask again: Was the event natural or was it global warming?
There is in this scenario entanglement. We have scientists, journalists, and politicians. I have explicitly used the plural form to suggest that there are many perspectives, many points of view, many purposes represented. Because of the presence of political interests, the question is being asked in a social environment that is more political than it is scientific.
In the previous entry, I wrote, “It is hard to see how playing the game of defining extreme events and then attributing that event to ‘climate change’ can ever be won. In fact, it seems like it is a game that necessarily leads to controversy, and controversy is the fuel of talk radio, blogs propagating around the world, and the maintenance of doubt.” The game to which I refer is described above: event, fast public attribution of the event to climate change, scientific investigation and deliberation, scientific conclusion that the event is not wholly-and-solely due to climate change. In the formal and informal media, this game devolves to:
“This event is the proof of global warming,” followed some months later by, “No it is not.”
You can read the previous entry on why I maintain trying to attribute a single event to climate change with a yes-or-no answer or to split our weather into natural-and-changed is not scientifically sensible. That does not mean, however, that we should not study extreme events and place them into context with history, a warming climate, and how they inform our future. In fact, I have maintained that one of the most important tasks for climate scientists to take on is the quantification of variability that is “short-term” compared with the “long-term” normally associated with climate. (See Some Jobs for Modelers, and Ocean, Atmosphere, Ice and Land) Which brings me to “attribution.”
In the discourse described above, amongst the politicians, journalists, and scientists, “attribution” has risen to mean, “Can this event be attributed to climate change?” Sometimes it is worth going back to basics. From the American Heritage Dictionary of the English Language attribute is “to relate to a particular cause or source.” And from the Glossary of Terms of the Intergovernmental Panel on Climate Change
“Detection and Attribution: Climate varies continually on all time scales. Detection of climate change is the process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change. Attribution of causes of climate change is the process of establishing the most likely causes for the detected change with some defined level of confidence.”
In fact, neither of these definitions require a yes-or-no, wholly-and-solely answer that a particular event was “caused” by the warming of the planet by increasing greenhouse gases. That requirement has risen from the quagmire of the public discourse.
In the piece Some Jobs for Modelers I talk about “forecast busts.” These are well known to weather buffs, when weather forecasts fail. It is worst when severe weather shows up unexpectedly. In December of 1999 there was a series of Atlantic storms that hit France which were badly forecast. Detailed examination of the observations, the forecast model, and the ability of model to utilize those observations, revealed that there was adequate information to provide a better forecast. Specific failures in the forecast system were identified. (A complicated paper on those storms: Dee et al. 2001) When I think of attribution and a single extreme event, then I think of the detailed scientific investigation of the processes that come together at the occurrence of that event.
There are many reasons to pose such a study. A basic reason is to understand the physical processes. For example, in a historic heat wave, what is the impact of regional changes in the forest, agriculture, and the urban environment? What are the specifics of the atmospheric flow that allow the development of a period of persistent heat? A perfectly legitimate question is whether or not changes in our environment related to greenhouse gases have had a discernible influence on the event.
So that becomes the question. In the complex mix of processes that are responsible for determining the temperature and winds and rain of an extreme event, is there a discernible contribution that can accounted against, attributed to, climate change? To make it more challenging, climate change is not a simple, unrelenting, uniform warming of the surface. Therefore, if there is to be a discernible signal, then it has to rise above the variability, the noise, that is implied by the complexity described in the previous paragraphs. It is not a question of whether or not an extreme event is caused by climate change, it is what influence might be attributed to the increase of greenhouse gases.
That said, there are many reasons to investigate which processes, which causes, are responsible for an extreme event. A fundamental one is to improve the ability to predict the event. Another reason is to understand the impact of the event, assess the risk associated with such events in the future, and, if warranted, develop the ways to better prepare for such events.
I want to return to the my previous blog, which was motivated by a story that originated in the Green Blog by John Rudolf on the New York Times website (March 9, 2011) about the Russian heat wave in the summer of 2010. The news story reported on a paper by Randy Dole and co-authors. Within hours the Dole et al. paper was headlined on both news sites and in blogs that the paper said that the 2010 Russian heat wave had no relation to global warming. It is a source of continuing and intensifying controversy. ( from Climate Progress, recall that above, I deliberately used the plural of scientist.)
Here is the link to the abstract of Dole et al., Was There a Basis for Anticipating the 2010 Russian Heat Wave? Dole et al. take an approach to the problem that is process-based, in the spirit of the process-based approach to a busted forecast. They search for the signal over the noise, and for the 2010 event cannot state definitively that the signal related to the increase of greenhouse gases exceeds the noise. I want to quote, however, two sentences from the “Concluding Remarks” of Dole et al.
“The results suggest that we may be on the cusp of a period in which the probability of such events increases rapidly, due primarily to the influence of projected increases in greenhouse gas concentrations.”
And looking forward.
“However, as is the case of the 2010 Russian heat waves, events will also occur that are not readily anticipated from knowledge of either prior climate trends or specific climate forcings, and for which advance warning may thus be limited.”
The Dole et al. paper does not state in any way that global warming is unreal. Quite the contrary, they work in a rigorous physics-based approach and investigate this region, at this time, for this event, and ask in the context of a forecasting problem, can a discernible contribution be attributed to human-caused greenhouse gas emissions? Their method, their analysis, their conclusions - that for some highly particular reasons - the climate change signal has not popped out of the natural variability. But as they say, it has in other places, for other phenomena.
Dole et al. provide one scientific approach to the problem of event attribution. There are other approaches. (see Barriopedro et al. The Hot Summer of 2010: Redrawing the Temperature Map of Europe) The conclusions from these results are likely to be different, and that difference may appear inconsequential to some and enormous to others. And while these differences might appear as important to scientists, my point is that this process of event attribution is a place where the scientific investigation of the climate interfaces, strongly,with the media. Therefore, it is also a place where, by definition, scientific investigation interfaces with the political argument. Politically or in terms of informing the public, a primary result of this process is to build, amplify and maintain doubt. Here, I have tried to reframe attribution. Next, on reframing the dialogue.
Previous blogs on the disruptions and communications of climate science. (or how can climate scientists contribute to political discrediting of science.)
Strength in Many Peers
“Have you no sense of decency, sir, at long last?”
What to Do? What to Do?
If Lady Chatterley’s Lover, then …
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Updated: 21:03 GMT le 27 Mars 2011
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Perils and Pitfalls of Event Attribution
Perils and Pitfalls of Event Attribution
Some of you may have noticed a story that originated in the Green Blog by John Rudolf on the New York Times website (March 9, 2011) about the Russian heat wave in the summer of 2010. The news story reports on a paper to appear in Geophysical Research Letters by Randy Dole and co-authors who conclude that in the historical record there is evidence of similar events of comparable intensity. It follows, they argue, that the Russian heat wave cannot be attributed to climate change – rather it is a very rare event. (Paper at GRL website, NOAA Description of Dole et al. article, Jeff Masters blog and analysis) For a variety of reasons I followed how this story propagated around the blogs and news services for the next 24 hours. It was picked up by many sites including, quickly, by the (according to comment writers on this blog) mysterious Steven Goddard (any more on that story?).
As it happens, I am writing an article for Earthzine with Christine Shearer on how scientists and the media engage each other about extreme events (Shearer blog on WU). When it is ready, I will proudly announce it and provide a link. That article will focus on a sociological analysis of extreme weather and the media. This blog will touch on a couple of the issues we raise in that article, but mostly it will be a scientist's point of view on the discussion of the value of pursuing the attribution of single events to climate change in a context largely described by public discourse.
Event Attribution: A public question that arises after every new extreme event is: can this event be attributed to climate change? At this point in time, I cannot imagine the answer to that question ever being, convincingly, yes. Scientists often rely on the statement: no single event can be attributed to climate change, but this event is not inconsistent with climate change. I have used that answer; perhaps, I repeat the mantra (Pakistan: A Climate Disaster Case Study). On thinking about that answer, it is more than useless. But then thinking about the question, it is, depending on your point of view: a natural question, a naïve question, an ill-posed question, or a leading question.
Why do I say that I cannot imagine the answer to such an event attribution question being convincingly yes?
Dole et al. study attribution, and they do it magnificently. Their strategy is to do a physical, statistical, and process analysis of historical information. If they find like events in the historical data, then that makes it impossible to attribute the event, wholly and solely, to climate change. This implies an odd metric: an event that is “caused” by climate change must be different than any event that has been previously measured. Do we have to have some Day After Tomorrow event where physical principles are suspended and the world moves to a whole new set of behavior?
The probability that looking through all of the observations, all of the history, that you are going to find a “like event” is high. I say “like event,” because there will be some differences no matter what. Of course, it has been hot in Moscow before, so there is some atmospheric pattern that yields “hot in Moscow.” We find like events and then, maybe, the current event is 10 degrees hotter and two weeks longer; it’s a obvious record. But is it climate change?
More likely than a obvious record, there will be another event that is similar, about the same, but not quite. Then it becomes the same question as, was Henry Aaron better than Babe Ruth? Aaron hit more home runs, but there are lots of other differences that experts point to and argue about: length of season, quality of pitching, … . Throw in Barry Bonds and Mark MacGwire; they hit a lot of home runs. Well maybe the physics (or physiology) of Bonds and MacGwire are different? Is climate change weather on steroids?
Suppose you look through the record and find that the current event is 10 degrees warmer and 2 weeks longer. Is it climate change? Do you know whether or not that if you had just one more year of observations, that you would not find out that that next year had a similar hot period. What about similar events in the medieval warm period? The data system was relatively sparse 100 years ago; maybe we just missed the event. So even if we find an event that is more intense, more persistent, then we have the problem - have we really observed the historical extremes? Have we observed all natural variability? This will always challenge the public and political discourse on event attribution - always.
More likely than finding an event that is extraordinarily different, we find an event that’s about the same length of time, but one degree warmer. Is the thermometer good enough? Are the instrument sites good - have they changed? What about the urban heat island? What about regional water management projects? Good scientific investigation and analysis can account for these issues, but in any event they are sources of differences, which as in the Aaron versus Ruth argument, are irreducible. Perhaps an extreme record can be established, but then, would that be climate change?
It is hard to see how playing the game of defining extreme events and then attributing that event to “climate change” can ever be won. It is often possible to isolate with statistical certainty descriptions that the emissions of greenhouse gases have influenced an event, but that represents one of those paths of nuanced explanation. Such nuanced explanation, again, assures there is not a definitive "yes" in the public and political discourse. In fact, it seems like it is a game that necessarily leads to controversy, and controversy is the fuel of talk radio, blogs propagating around the world, and the maintenance of doubt.
But what about that question of attribution? Let’s say you find an event that is rare, that is extreme, but not a new record - does that really say that the event today, right now, is not climate change?
In a very basic, old fashioned way, weather and climate are different descriptions of the same thing. They depend on how we, somewhat arbitrarily, define how we want to organize the observations. Crudely, we average weather to make climate. Since we work from the premise that climate change will be slow, for the most part the same type of weather events will make up the old (natural) climate and the new (changed) climate. Over time, the frequency of events will change, what were rare events in the old climate, might just be less rare events in the new climate. I pose, however, that even in a world that is on average four degrees warmer than today, there will be a seventy two degree, sunny day in the spring in Washington D.C. Do we then march through the days 50 years from now and say, “old climate,” “new climate?” The idea of isolating a single event on a single day or a persistent event and asking if it is caused by climate change – does that make sense? Is it even meaningful given the definition of climate? How did we arrive at the question of climate change being a causative of a weather event?
I want to restate the previous paragraph in a different way. Let’s assume that climate is averaged weather. Then climate is defined by a mean, a standard deviation, and a set of more sophisticated parameters that describe statistical distributions. What we have come to call the natural climate is defined by certain values of the mean and measures of deviations from the mean. The future, changed, warmer climate will have different values of the mean and the measures of deviations. With the presumption that the warming of the climate is incremental, then the majority of the events in the warmer climate will be like the events in the “natural” climate. Therefore, just because a like event existed in the "natural" climate does not mean that the current event is not part of the "changed" climate. There are NOT two climates - a natural one and a changed one - with our job being to determine if we have flipped from one to another. When we say that there will be more extreme events in the changed climate, it does not necessarily mean there will be a relentless unwavering string of records. There will, perhaps, be more events that have been previously rare. But, it is not climate change causing weather events.
As you study climate change, it becomes clear that talking about independent isolated events is not especially productive when trying to address attribution questions. Climate is an average, or perhaps better, an accumulation of weather events. As such it is important to consider how a large number of events act in concert, in correlation, in cohesion.
One other point that I want to make: The practice of isolating a single event and attributing that event to climate change, is one of the most effective ways of opening up scientific investigation to effective scientific criticism. (see Pielke, Sr. et al. 2007) A single-event attribution claim is an open and appropriate invitation to those with knowledge of or interest in local information to investigate the attribution claim. Almost inevitably this leads to identification of more sources of uncertainty, which like the Aaron versus Ruth argument, are irreducible. This necessarily contributes to controversy, and controversy is the fuel of talk radio, blogs propagating around the world, and the maintenance of doubt.
This entire process of event attribution is one place where scientific investigation of the climate interfaces with the media. Therefore, it is also a place where, by definition, scientific investigation interfaces with the political argument. My analysis above suggests that, as framed by the public discourse, the pursuit of the path of event attribution and the explicit or implicit linkage of that attribution to climate change is scientifically questionable. This stands in contrast to the scientific pursuit of extreme events in historical context and the evaluation of whether their frequency of occurrence is changing. Politically or in terms of informing the public, the primary product of the pursuit of event attribution is to build and maintain doubt. The exception to doubt maintenance would be if a definitive, metaphorical smoking gun was discovered. But what is the probability of such a smoking gun being discovered in this process? A different perspective is needed on the role of extreme events in climate and the attribution of such events to global warming. As climate scientists, we have to think about what these studies mean to the body of our field’s communication of climate change.
And here is
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Updated: 01:47 GMT le 27 Mars 2011
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