Les phénomènes météorologiques extrêmes, une conséquence des ...
Ainsi, au lieu de se demander si une vague de chaleur extrême est causée par les changements climatiques, ils évaluent les probabilités que les changements ...
quarantième coup de circuit
Inondations, feux incontrôlés, vagues de chaleur et sécheresses sont de plus en plus courants. Chaque fois qu’ils se produisent, nous nous demandons inévitablement : « Est-ce à cause des changements climatiques? » Or il semblerait que nous ne posons pas la bonne question; ce serait un peu comme se demander, à l’époque de l’apogée des stéroïdes dans la ligue majeure de baseball, si le <anchor>quarantième coup de circuit</anchor> de l’un des joueurs était attribuable à la prise de substances améliorant la performance. Dans les deux cas, en mettant l’accent sur un événement isolé, on oublie l’essentiel : l’élément qui gonfle les statistiques, qui inscrit les phénomènes exceptionnels dans notre nouvelle normalité.
The Death To One Of The Most Abused Questions Ever: Was That Caused By Climate Change?
BETA

This is a BETA experience. You may opt-out by clicking here

### More From Forbes

Jul 23, 2019,09:28am EDT

Jul 15, 2019,08:45am EDT

Jul 8, 2019,09:20am EDT

Jul 1, 2019,10:52am EDT

Jul 20, 2018,10:00am EDT

Jul 19, 2018,10:00am EDT

Jul 18, 2018,10:00am EDT

Jul 17, 2018,10:00am EDT

# The Death To One Of The Most Abused Questions Ever: Was That Caused By Climate Change?

Marshall Shepherd
Senior Contributor
Opinions expressed by Forbes Contributors are their own.

Mar 11, 2016,10:00am EST

Updated Mar 11, 2016, 01:46pm EST

This article is more than 8 years old.

- Share to Facebook
- Share to Twitter
- Share to Linkedin

With record rainfall in Louisiana and other parts of the south this week, inevitably someone is going to ask, "Was it caused by climate change?" I cringe when I hear this question because it is so abused by ALL sides of the climate discussion:

This is the cliche dance that plays out on Twitter, the media and elsewhere.

But Dr. Shepherd my _________( fill in the blank with: uncle, favorite blog, news network, favorite twitterologist) says it is a hoax, unproven and so-on. Once you filter through the noise, the signal is clear. The majority of peer review literature notes that there is a anthropogenic "steroid" on top of the naturally-varying climate. For example, home run frequency and length varied naturally in Major League Baseball, but after the Steroid era the influence was seen in the home run statistics. But was a certain baseball players 300th homerun caused by steroids? That's an ill-posed question. The  National Academy of Sciences released a report, Attribution of Extreme Events in the Context of Climate Change. Within its key findings, we find an expert plea to make the "Was it Caused By Climate Change" question extinct. Some key findings from the report are summarized, but the full 144-page report can be downloaded here. I was honored to be one of the experts that authored the report.

Asking the right questions. "Was that event caused by climate change?" just cannot be answered because natural variability almost always plays some role. When a team plays basketball, there is a natural variability in the outcome of each game, but as team practices and attains better players, there is a bit more "signal" on the potential outcome of the game. More appropriate questions are:

The factors used in rating attribution confidence. Source: National Academy of Sciences.

Some events are more attributable than others. Confidence is greatest for extreme events related to aspects of temperature (e.g. extreme heat and lack of extreme cold events). Attribution science is relatively young but has advanced rapidly. The National Academy panel noted that attribution is most reliable when there are sound physical principles, consistent observational evidence, and the ability for numerical models to replicate the event. These "three legs of the stool" were used as benchmarks to rate the confidence. Attribution of extreme rainfall and hydrological drought are found in the moderate confidence category. Why? There is good physical understanding of how the warming aspects might lead to greater evaporation rates (to further amplify a drought or make more water vapor available in a precipitating storm). There was only moderate confidence in the length of record and ability of model to simulate other aspects. There is little to no confidence in attribution of tornadic storms or Nor'easter-Mid-latitude cyclone type storms. There is emerging literature that may increase our confidence going forward, but the body of literature does not support a higher confidence rating at this time.

Danger Will Robinson, Danger. These ratings DO NOT mean that every single event is linked to climate change. It simply means that the science is now able to provide attribution with moderate to high confidence for a subset of events studied. The report also argues that future attribution studies need a set of standards to guide how cases are selected for study. There is a degree of randomness and opportunity in selection that hinders the broader representation of attribution studies.

Framing is also important.  The Russian heatwave of 2010 was discussed in the report. In the 1960s, it was a "once in a lifetime event" (every 100 years or so). It now has become, as Panel Chair Admiral David Titley says, a "once in a mortgage event" (every 30 years) according to published studies. However, if you frame it in terms of mean summer temperature, the increase over that period is a few degrees Fahrenheit. A few degrees is still significant to the climate system but to some it may not be perceived the same way as the framing with the return period. Oh by the way, the DC area is running a few degrees above normal right now and it is quite noticeable in early March (and would be in August for sure).

The report notes that attribution studies can eventually benefit from being linked to an integrated weather-to-climate forecasting effort on a range of time scales (0 to several years). The ultimate goal would be to provide predictive (probabilistic) forecasts of future extreme events at lead times of days, seasons, or longer. With this goal in mind, it is simply ridiculous to frame "weather research" vs"climate research." They need to be evaluated as a continuum.

Now for the last time.....