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Floods: the new same old

05 Jun 2019 | Science Notes

In its 2012 report on extreme weather the Intergovernmental Panel on Climate Change concluded that there was little evidence of changes in the magnitude and frequency of floods regionally and no agreement even about the direction of any global trend. A year later, many of the same experts put out a new paper to elaborate on the science. Their bottom line? Contrary to climate model predictions, "no [rain] gauge-based evidence had been found for a climate-driven, globally widespread change in the magnitude/frequency of floods during the last decades." As often on climate, you can believe the models or the evidence, but not both.

The article, in Hydrological Sciences Journal, points out that about 800 million people worldwide (11 percent of global population) live in flood-prone areas, and about 70 million are exposed to “flood events” each year. It’s useful information to keep in mind when the news shows, as it inevitably will, massive flooding in some unfortunate part of the planet each year. It may be devastating. But it’s not new or unusual, and though floods can be terrible they are unavoidable when so much of the world's population lives on floodplains. The alarmists love the phrase "the new normal" to describe such scenes but they’re only half right: It's normal, but it's not new.

In Canada and the US there are regional patterns in heavy precipitation, but overall they reiterate the earlier IPCC paper (known as “SREX” for “Special Report on EXtreme events”) conclusion: "In the United States and Canada during the 20th century and in the early 21st century, there is no compelling evidence for climate-driven changes in the magnitude/frequency of floods."

Mindful, perhaps, of the gap between perception and reality, the paper devoted some attention to the question of why people have come to believe there are more floods than ever before. The authors point to the media as the likely reason (though one could certainly also indict politicians):

"Media play a role—the news coverage is much better, worldwide, than in the past and tends to be focused on the negative side of things... Some call it a 'CNN effect.'"

The alarmist media creating a distorted picture of things? The new normal--same as the old normal.

2 comments on “Floods: the new same old”

  1. Supporting the media reporting on floods is the everywhere camera. Phone cameras, TV cameras and cameras on drones are providing videos of panoramic views of floods. Now anyone trapped in a car on a flooded road is video taped by someone. The videos are dramatic and very impressive, portraying without a doubt that the cause is climate change - despite the fact that flood plains have been flooding for many years. The Mississippi River levees were being built over 150 years ago.

  2. The proliferation of photos and videos also feeds the 'availability bias' of the public - that is, instead of looking at data and statistics about extreme weather or flooding extremes, people rely on how many sensational events they can recall to assess trends. Daniel Kahneman identifies many heuristic biases in his book Thinking Fast and Slow. I've illustrated how several such cognitive short-cuts play out in the media surrounding this topic in a paper called "Evidence Based Policy Gaps in Water Resources: Thinking Fast and Slow on Floods and Flow" in the Journal of Water Management Modeling https://www.chijournal.org/C449.

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