Penn State University
Extreme weather events like floods, heat waves and droughts can devastate communities and populations worldwide.
Recent scientific advances
have enabled researchers to confidently say that the increased intensity and
frequency of some, but not all, of these extreme weather events is influenced
by human-induced climate change, according to an international National
Academies of Science, Engineering, and Medicine report released March 11.
"In the past, many scientists have been cautious of
attributing specific extreme weather events to climate change. People
frequently ask questions such as, 'Did climate change cause Hurricane Sandy?'
Science can't answer that because there are so many relevant factors for
hurricanes. What this report is saying is that we can attribute an increased
magnitude or frequency of some extreme weather events to climate change,"
said David Titley, professor of practice in Penn State's Department of
Meteorology and founding director of Penn State's Center for Solutions to
Weather and Climate Risk, who chaired the committee that wrote the report.
The committee found that scientists can now confidently attribute some heat waves and cold events, and to a lesser degree droughts and extreme rainfall, to human-caused climate change. Even a decade ago, many scientists argued that research could not confidently tie any specific weather events to climate change, which the committee reports today is no longer true today.
"If we can actually understand how and why frequencies or
magnitudes change of extreme events are changing, those are two components of
risk. Understanding that risk is crucial for governments and businesses. For
example, if you're managing a business, you may need to know whether there may
be more droughts in the future because that may impact supply chain logistics
and, ultimately, your bottom dollar," said Titley.
Scientific confidence for attributing extreme weather events is
a three-legged stool, said Titley. To confidently link specific weather events
to climate change, researchers need an understanding of the underlying physical
causes of weather events, enough observational data to place a specific event
within a historical context and the ability to replicate an event with computer
models.
For example, when examining hurricanes and typhoons, the lack of a
high-quality, long-term historical record, uncertainty regarding the impact of
climate change on storm frequency and inability to accurately simulate these
storms in most global climate models raises significant challenges when
attributing assessing the impact of climate change on any single storm.
Attributing the cause of extreme weather to climate change or
other factors can "enhance scientists' ability to accurately predict and
project future weather and climatic states," said Titley. Predicting both
the frequency and intensity of extreme events -- those that are rare in a
location -- could allow society to lessen their impact and potentially avoid
loss of life and destruction.
The committee identified research priorities to further enhance
the scientific community's ability to attribute specific extreme weather events
to climate change. In addition to endorsing action on relevant items outlined
by the World Climate Research Programme in 2014, the report recommends developing
transparent community standards for attributing classes of extreme events, and
formulating systematic criteria for selecting events to be studied.
The
committee also recommends that some future event attribution activities could
be incorporated into an integrated weather-to-climate forecasting efforts on a
broad range of timescales, with an ultimate goal of providing predictive
risk-based forecasts of extreme events at lead times of days to seasons.