Science Links Some Violent Weather to Human-Induced Climate Change

An emerging branch of science can now link human-caused climate change to some specific extreme-weather events, according to a new report.
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A mere eight years ago, climate scientists were hard put to pinpoint the influence of climate change on weather events such as hurricanes. But researchers are crossing that barrier, and a team of scientists announced last week that some extreme weather events can definitively be linked to climate change.

In general, so many factors are at play in any given weather event that it has been difficult, if not impossible, for scientists to say that climate change caused droughts, floods, storms, heat waves or any single weather event—in short, science has had no firm answers. But that’s no longer the case. Researchers can now say with confidence that the increased intensity and frequency of some of these extreme weather events is influenced by human-induced climate change, the National Academies of Science, Engineering and Medicine reported on March 11.

“An increasingly common question after an extreme weather event is whether climate change ‘caused’ that event to occur,” said committee chair David W. Titley, professor of practice in meteorology and founding director of the Center for Solutions to Weather and Climate Risk at Pennsylvania State University, in a statement. "While that question remains difficult to answer given all the factors that affect an individual weather event, we can now say more about how climate change has affected the intensity or likelihood of some events.”

Scientists are most confident about reporting the links between climate change and some heat waves and cold events, droughts and extreme rainfall due to sufficient historical evidence, and the ease in recreating simulations of these events. There is less proof about the effects of climate change on other events such as tornadoes, wildfires and hurricanes. It's all outlined in the report, Attribution of Extreme Weather Events in the Context of Climate Change.

“Science can't answer that because there are so many relevant factors for hurricanes,” said Titley, a retired admiral, in the statement. “What this report is saying is that we can attribute an increased magnitude or frequency of some extreme weather events to climate change.”

For instance, an individual wildfire’s intensity and occurrence depends on past forest management, natural climate variability, human activity in the forest and possibly other factors, in addition to any exacerbation by human-caused climate change.

Nonetheless, this relatively new area of science—often called event attribution—is advancing quickly because the understanding of the climate and weather mechanisms that produce extreme events is improving, and because of rapid progress in the methods that are used for event attribution. 

Not every type of event discussed in the report is a pure meteorological event. Droughts, floods and wildfires all have human, as well as natural, components. Land management, controlled burning, and dams and levees affect the magnitude and frequency of these extreme events. However, the authors believe there is a large weather and climate signal to these types of events. Learning more about that can help people and governments assess risk, determine whether to rebuild after a severe storm such as Sandy, and create policy, they said.

"If we can actually understand how and why frequencies or magnitudes change of extreme events are changing, those are two components of risk,” said Titley, a retired admiral, in a news release from Penn State. “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.”

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