Analogies for attribution of extreme events

8 Aug 2017

Unlike other research fields where the work is performed with tangible samples and materials, attribution studies of extreme weather events don’t offer that possibility, which make them sometimes quite difficult to understand.

The analyses carried out by meteorologists and climatologists usually involve huge amounts of data which seem abstract until you make sense of them, identify what you are looking for, and present the results in a visual and comprehensible way.

Through the review of the literature of attribution studies of extreme weather events, it is possible to find analogies to make the basis and methodology of theses studies easier to understand by comparing them with possible everyday  activities or actions.

Maybe the first and most well known analogy is the one of Professor Myles Allen of the loaded dice (you can watch the seminar Loading the dice: climate change and extreme weather in our former post). If you repeatedly roll several dice, it can happen that initially everything seems normal, nothing extraordinary. However, if you look twice, more carefully, you will soon realize that the number six seems to occur frequently. Of course, this could be by chance, but it could also be associated to other factor/s which would explain this apparently extraordinary number of sixes. But in order to discover that, you would have to roll the dice quite a few times to get to know the chances of obtaining so many sixes from all the rolls of the dice. So, in attribution of extreme events, it is also needed to run the model over and over again in order to obtain multiple results (ensembles) that can be analyzed in order to be able to draw some conclusions.

Another analogy appeared in the Bulletin of the American Meteorological Society (BAMS) of 2014 (Herring et al., 2014), whose vision of how this new research field works is reflected in a video entitled Steroids, baseball, and climate change. Before you watch it, here is the outline. Imagine a baseball player who starts taking steroids. After that, he hits an average of 20% more home runs than before and so probably you would attribute this amazing improvement to the steroids. But was this the only factor which changed during that period? Maybe, he was able to spend more hours training, hired a new trainer, or changed his diet. But if all those factors didn’t change, we can say that the steroids are the responsible for that increase in the probability of him hitting more home runs.

(©UCAR. Video by Noah Besser, produced by UCAR Communications for AtmosNews: NCAR & UCAR Science. This video is freely available for media and nonprofit use.)

The BAMS issue of 2013 (Peterson et al., 2013) echoed another analogy from the University Corporation for Atmospheric Research (UCAR, 2012). In this case they use a car instead of a baseball player. If we go every day to work by car, but we increase the speed of our journey, the greater the speed, the more the likelihood of us having an accident. However, if this event unfortunately happens, it may not be due to the speed. It could be related to bad weather, another driver speaking by phone, an obstacle in the road… In this case atmospheric greenhouse gases are analogous to the speed. We can study the odds of having such an accident at a particular speed but also taking into account some of the other factors. That’s to say, maybe the speed was a key factor in the accident, but some other aspect could have played a role too (this is akin to natural climatic variability).

In these two cases is clear that greenhouse gases could have being playing a role (steroids, speed), but that there are many other factors which could be influencing the result to some extent. However, understanding how greenhouse gases affect the likelihood or magnitude of an extreme weather event is a key step in the decision making process and the adaptation and mitigation measures for the long term, which should be still effective in 50 years’ time or more.

The third and last analogy is that of the cookies. This more recent analogy is based on the book Attribution of Extreme Weather Events in the Context of Climate Change from The National Academies of Sciences, Engineering and Medicine, about which we have already talked in our post Getting to know attribution studies: basic concepts and referencesDave Titley, Committee Chair of the Board on Atmospheric Science and Climate, gave a presentation entitled: Attribution of Extreme Weather Events in the Context of Climate Change within the framework of the Report Release Briefing on the 11th March 2016. You can read and download Dave Titley’s  presentation in the following link:

Also, here is the fragment of Dave’s talk so you can understand better the slides:

One of the slides it is called A Banking Analogy. In this case one cookie is the event, similar to the home run or the accident by car in the other cases. All the factors that are involved in this case are the ingredients of the recipe, and they may or may not be responsible to some extent for the output, which can be different according with the proportions of the different constituents involved: quantities of the ingredients, temperature of the oven,… This analogy is fully explained in the following video:

Even though climate models may be intangible, I hope you can have a better understanding of attribution science of extreme weather events. So, here is a video where you can apply what you have learned so far and put all the pieces together to become aware of the importance of this methodology and the outcomes it can offer us in order to be prepared for a changing climate.

 This video is presented by the Climate & Development Knowledge Network (CDKN), who has an initiative to raise risk awareness in the developing countries. This Raising Risk Awareness initiative uses “state-of-the-art science to help Asian and African societies to understand the role of climate change in extreme weather events and prepare for future ones“.

If you feel now that you can be a part of the development of this exciting new field of research and want to contribute to the objective of ClimAtt, you can do it through the World Weather Attribution (WWA) project. Please, just click on the following image:

This project depends upon enthusiastic volunteers, citizen scientists who contribute to improvements in the science of attribution of extreme weather events and make a positive impact in societies around the world by offering some computing time.



Climate Change Attribution of Extreme Weather Events