Did climate change cause Louisiana’s flooding?

The New York Times, Al Gore, Vox, Congressman Raul Girjálva, Chris Mooney (citing evangelical climate-alarmist darling Katharine Hayhoe) in the Washington Post, and lots of others in the mainstream media think so.

But more sober voices disagree. Adam Sobel of the Earth Island Institute at Columbia University, no “climate-change skeptic,” writing at Phys.org, says,

no study can tell us that climate change caused an event like this to happen, full stop. Every weather event has many causes. Climate change is just one of them, and usually not the most immediate. At most it can push things a bit in one direction, making the weather more severe if it was going in that direction anyway.

He predicts that attribution studies now underway

once done, will show an increase in the probability of occurrence of an event of this magnitude, as a result of increasing water vapor making all heavy rain events heavier. But it’s not guaranteed that they will have this result, because the amount of water vapor isn’t the only thing that matters. Other factors involved in this weather system could, conceivably, change in such a way as to make its occurrence less likely in the first place, counteracting the effect of increased water vapor in the event that it did happen.

Climatologists Patrick Michaels and Chip Knappenberger of the Cato Institute, who self-describe as “lukewarmers”—believing human greenhouse gas emissions contribute significantly to global warming but that the effect will not be catastrophic, cite two recent studies that challenge the claim that global warming will lead to more frequent or severe extreme weather events like the Louisiana flooding. “One paper by a research team from the University of Iowa,” the write,

found that “the stronger storms are not getting stronger” and that there has not been any change in the seasonality of heavy rainfall events by examining trends in the magnitude, frequency, and seasonality of heavy rainfall events in the United States. They did report that the frequency of heavy rain events was increasing across much of the United States, with the exception of the Northwest. As to the reason behind the observed patterns, the authors write “[o]ur findings indicate that the climate variability of both the Atlantic and Pacific Oceans can exert a large control on the precipitation frequency and magnitude over the contiguous USA.”

I.e., events in the oceans do more to influence rainfall than climate change.

“The other paper, from a research team led by NOAA/GFDL’s Karin van der Wiel,” they write,

examined climate model projections and observed trends in heavy precipitation events across the United States and concludes: ‘Finally, the observed record and historical model experiments were used to investigate changes in the recent past. In part because of large intrinsic variability, no evidence was found for changes in extreme precipitation attributable to climate change in the available observed record.’ Pretty emphatic and straightforward summary. So, the next time you read that such and such extreme precipitation event was made worse by global warming, you’ll know that there is precious little actual science to back that up.

But it matters little to the Chicken Littles who control climate-change discussion in the MSM. They’ll keep up the drumbeat regardless of the lack of substantial scientific support.