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When it comes to weather, optimism bias can lead to danger

Don Paul

Many times optimism is well supported with evidence when dealing with weather. For a few consecutive days, guidance has been continuing to suggest a warm home opener for the Bills against the Bengals Sunday at New Era Field. There should be a brisk southwest flow bringing well-above-average temperatures.

There is high confidence that both Saturday and Sunday will feature nearly summerlike high temperatures.

The meteorological optimism may have to be tempered a bit by the approach of the cold front – seen in the first map – which could trigger a few afternoon and, more likely, evening showers.

There is a different kind of optimism that sometimes prevails in advance of major weather events and is not based on such good evidence. Optimism bias is more a matter of hoping for the best, based on more or less favorable memories of past experiences.

J. Marshall Shepherd, director of atmospheric sciences at the University of Georgia, wrote on this topic last week for his column in Forbes magazine. One of Shepherd’s main points is that optimism bias will more often bear bad fruit in the face of climate change and our mean warming climate. Extreme weather events, including heat waves, have been increasing in many locations (fortunately Western New York has not seen much in the way of extreme heat).

Although air conditioning is finally becoming a little more common in Europe, there has been an optimism bias on that continent based on past climatology that used to demonstrate a typically more tolerable range of summer heat. That anti-AC bias, which is also linked with energy conservation in many European nations, was part of the reason as many as 70,000 deaths occurred in western Europe during a deadly heat wave in 2003. This summer all-time high temperature records were set in France, Belgium, Spain and the Netherlands in late June. The French health minister reported around 1,500 deaths during that shorter heat wave, compared to the 15,000 French who died in the horrible 2003 heat wave.

Relying on smoother past climatology and past events during this time of a mean warming climate has other potential hazards that can place large populations in peril. Every hurricane is different, but there is a wealth of evidence our warming oceans will lead to more intense hurricanes (not more hurricanes in total). There was the recent Hurricane Dorian, with its maximum winds of 185 mph over Abacos and Grand Bahama islands. In the case of this disaster, there was abundant advance warning for the islanders, but many had no safe place to go with such ferocity in a monstrous stalled hurricane.

Then, there is the increasing prevalence of stalled weather systems due to weak upper level steering winds tied to arctic warming and its weakening of these winds and the jet stream.

As I wrote in The Buffalo News on Sept. 4: “In particular, the predicted and verified greater warming in the arctic is now known to have frequently weakened upper air winds, including tropical steering currents by lessening the thermal contrast between the polar region and mid- and lower latitudes. This lessened contrast slows those winds, and models are picking up on this new climatology. The virtual stalling of Dorian near the Bahamas was well predicted by global models days in advance of its occurrence. Similar model forecasts were made with the second costliest hurricane to hit the U.S. of all time, Harvey, in 2017 and Florence in the Carolinas last year. There is already confirmed evidence these stallings are occurring with greater frequency as warming has accelerated. As reiterated by Jennifer Francis, formerly with Rutgers and now with the Woods Hole Research Institute, who told the New York Times: 'This is yet another example of the kind of slow-moving tropical systems that we expect to see more often as a response to climate change. Upper-level steering winds are slowing over the continents during summer, so stalling weather systems are more likely.' "

In the case of 2017’s Harvey, warnings went out well in advance that a weakened Harvey would stall just inland and produce highly destructive floods. Social surveys reveal many Houstonians had an attitude of “it floods here all the time, so it’s not that big a deal.”

As we now know, the $125 billion in property losses proved otherwise. Past climatology gave a partial false sense of security, even in the face of explicit advance flood warnings from the National Weather Service.

A man waves down a rescue crew as he tries to leave the area after it was inundated with flooding from Hurricane Harvey on Aug. 28, 2017, in Houston. (Joe Raedle/Getty Images)

Even when Dorian began making its trek to the Outer Banks of North Carolina in a “weakened” state, it remained a major threat to life and property. When the storm was still offshore from Florida, the National Hurricane Center warned of “life-threatening” coastal flooding and storm surge for the southeastern U.S. coast, and specified major flooding also would hit the North Carolina Outer Banks from Pamlico Sound to their west, between the islands and the mainland just after the eyewall began to pull away. Beautiful Ocracoke Island, just south of Hatteras, had 800 residents who chose to ride it out. Ocracoke has ridden out quite a few past hurricanes with less-than-devastating damage, and these people chose to rely on past experience in their refusal to leave.

Greg Carbin, a friend and chief forecaster at NWS headquarters tweeted this NOAA GOES satellite before and after, with Ocracoke on the left and Hatteras on the right.

Amazingly, none of the residents were hurt or injured. But property, road and beach damage was massive. By way of a defense of the islanders, with the lesser impacts in recent past hurricanes, many knew they would need to get into their homes and businesses immediately afterward and begin disinfecting to prevent mold and more permanent damage. In fact, those few who did evacuate were unable to return for days to begin recovery work because state ferry service had halted. Ocracoke is accessible only by ferry and a tiny airstrip. Some residents claim they did not expect the Pamlico Sound storm surge, even though that threat was explicit in the NHC advisories and local NWS forecast.

The main point here is we cannot rely on 100-year floods to remain 100-year floods, nor other rare weather extremes to remain so rare. We are fortunate here in Western New York that these extremes are not often life-threatening.

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