Are climate scientists being too cautious when linking extreme weather
to climate change?

Date:
October 16, 2020
Source:
University of Washington
Summary:
Climate science has focused on avoiding false alarms when linking
extreme events to climate change. But it could learn from how
weather forecasters warn the public of hazardous events to include
a second key metric: the probability of detection.



FULL STORY ==========================================================================
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 public are asking when these extreme
events can be scientifically linked to climate change.


==========================================================================
Dale Durran, a professor of atmospheric sciences at the University of Washington, argues that climate science need to approach this question
in a way similar to how weather forecasters issue warnings for hazardous weather.

In a new paper, published in the October issue of the Bulletin of the
American Meteorological Society, he 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. How can the atmospheric sciences community find the right balance? Most current
approaches to attributing extreme weather events to global warming, he
says, 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 probably 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.

Probability of detection has mostly been ignored when it comes to linking extreme events to climate change, he says. 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." Why does this matter? The paper concludes by noting: "If a forecaster fails to warn for a tornado there may be serious consequences
and loss of life, but missing the forecast does not make next year's
tornadoes more severe. On the other hand, every failure to alert the
public about those extreme events actually influenced by global warming facilitates the illusion that humankind has time to delay the actions
required to address the source of that warming.

Because the residence time of CO2 in the atmosphere is many hundreds to thousands of years the cumulative consequences of such errors can have
a very long lifetime."

========================================================================== Story Source: Materials provided by University_of_Washington. Original
written by Hannah Hickey. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Dale R. Durran. Can the Issuance of Hazardous-Weather Warnings
Inform the
Attribution of Extreme Events to Climate Change? Bulletin of
the American Meteorological Society, 2020; 101 (8): E1452 DOI:
10.1175/BAMS-D-20- 0026.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201016123916.htm

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