“So climate change makes formerly severe, rare events occur more often,” she said.
The conclusions in the latest IPCC report, released Aug. 9, represent a major change from the last IPCC report before that, released in 2013. Then, IPCC found only a low confidence that changes in global drought patterns could be attributed to human influence.
But since 2013, climate change including global warming has gotten worse, “and we’ve actually started to see extreme events like droughts, floods and heat waves” far more often, Tierney said.
Also, an increasing number of studies have concluded that climate change is connected with drought severity, she said. Scientists also have developed a technique of attribution studies in which they can figure out how much did global warming affect a particular extreme climactic event, she said.
The technique has been used for detecting human influences not just on droughts but on heat waves and on heavy precipitation events, she said.
The ability to attribute individual events to long-term climate change has also benefited from increased use of what’s known as paleoclimate information that uses rocks, tree rings, leaf margins, certain types of minerals, warm water animal occurrences and stable isotopes of oxygen.
UA’s Tierney’s own specialty is paleoclimate studies in which she uses mostly sediments, mud collected from ocean bottoms, and sometimes rock outcroppings, to study past climates.
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