These researchers, including some who have peddled the hypothesis in various forms for many years, came together to issue a “rapid attribution study” that alleges the odds of a “50-year” storm in reality have dropped to more like occurring every 30 years because of man-made global warming. Intended for publication in a scientific journal, this kind of submission, in the authors’ words, “arises from the current intense public discussion that results from the significant societal impacts of this particular event” reporting results recently after an extreme event may enhance the societal understanding of climate change and extreme weather, and provide often requested information for management decisions following the event.”
In other words, don’t let a crisis go to waste: appropriate it as fodder to advance the data- and theoretically-challenged man-made global warming crusade. Even if this effort really cannot do that: as the authors note, “specific scientific statements for the event as observed in south Louisiana cannot be made based on general assessments of the connection of global warming and extreme rainfall.”
Regardless, the researchers then pull a couple of models off the shelf and try to do this – despite the fact that these using past data have performed poorly in forecasting temperature variations, joining the universe of such models. That’s because the dynamics contributing to climate are very poorly understood. For example, a component of this pair that purports to explain temperature variations, the El Nino Southern Oscillation, almost never gets predicted correctly in appearance, timing, or strength. In other words, the models see it as essentially a random event. This could influence tremendously temperature or not at all; scientists simply do not know.
Further, models become notoriously poor in explanatory power when applied to basically local areas. This study does precisely that, using models with low predictive abilities when applied to larger geographies and shoehorning these into an area 20 square degrees of latitude and longitude.
Finally, the data used have extreme limitations. The researchers go back over a hundred years, to a period where almost no stations reported data and infrequently, with concerns about the reliability of those observations. Only in recent decades does a genuine critical mass of observations at a number of stations develop. The researchers recognize this by analyzing mainly the period after 1930, even as they create a baseline on sketchy data several decades earlier, and then heap plenty of caveats about the results.
In short a model of dubious quality because science understands decently the impact of carbon dioxide on climate change and not much else, used by researchers who have established academic careers by advocating for the existence of significant anthropogenic climate change, under the auspices of the National Oceanic and Atmospheric Administration that has shown increasing signs of politicization in its efforts to propagate this agenda, in a field increasingly intolerant to those who poke the many holes extant in the hypothesis, declares it has found evidence of the biases of those who back such models. With all due respect, in evaluating the work from a larger scientific perspective such a conclusion must be regarded as extremely tenuous and more likely a garbage-in, garbage-out phenomenon than an accurate assessment of the situation.
Thus, policy-makers relying upon this information need to understand it in the following context: it does not come close to proving man-made global warming exacerbated that rainfall, and does nothing to convert the hypothesis from its faith-based status into actionable science.