Published Monday, October 19, 2020
Scientists are cautious when linking
extreme weather to climate change,
By the A.M. Costa Rica wire services
In this year of extreme weather events, from devastating West Coast wildfires to tropical Atlantic storms that have exhausted the alphabet, scientists and members of the community are asking when these extreme events happen, for them to cautiously be scientifically linked to climate change, a study of the University of Washington said.
Dale Durran, a professor of atmospheric sciences at the University of Washington, argues that climate science needs to approach this question in a way similar to how weather forecasters issue warnings for hazardous weather.
Durran draws on the weather forecasting community's experience in predicting extreme weather events such as tornadoes, flash floods, high winds and winter storms. If forecasters send out a mistaken alert too often, people will start to ignore them. If they don't alert for severe events, people will get hurt.
Most current approaches to attributing extreme weather events to global warming, he said, such as the conditions leading to the ongoing Western wildfires, focus on the likelihood of raising a false alarm.
Scientists do this by using statistics to estimate the increase in the probability of that event that is attributable to climate change. Those statistical measures are closely related to the "false alarm ratio," an important metric used to assess the quality of hazardous weather warnings.
But there is a second key metric used to assess the performance of weather forecasters, he argues "the probability that the forecast will correctly warn of events that actually occur, known as the "probability of detection."” The ideal probability of detection score is 100%, while the ideal false-alarm rate would be zero.
The probability of detection has mostly been ignored when it comes to linking extreme events to climate change, he said. Yet both weather forecasting and climate change attribution face a tradeoff between the two. In both weather forecasting and climate-change attribution, calculations in the paper show that raising the thresholds to reduce false alarms produces a much greater drop in the probability of detection.
Drawing on a hypothetical example of a tornado forecaster whose false alarm ratio is zero, but is accompanied by a low probability of detection, he writes that such an "overly cautious tornado forecasting strategy might be argued by some to be smart politics in the context of attributing extreme events to global warming, but it is inconsistent with the way meteorologists warn for a wide range of hazardous weather, and arguably with the way society expects to be warned about threats to property and human life."
How can the atmospheric sciences community find the right balance? We would like to know your
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