Extreme events all over the world were marked by the influence of climate change in 2018: wildfires in California, heat waves in Europe and Asia, and record-low sea ice in the Arctic.
That’s according to an annual special report released yesterday in the Bulletin of the American Meteorological Society. The report, now in its eighth year, includes a collection of studies analyzing major events to determine whether climate change played a role—a field of research known as attribution science.
Typically, each report includes a number of events in which climate change had a significant influence—and a few in which it didn’t. But as the years go on, a trend seems to be emerging. More and more studies are finding the fingerprints of global warming on disastrous events.
Since 2011, when the first special bulletin was published, it’s “steadily seen an increase in the percentage of papers that find an influence versus not,” NOAA climate scientist Stephanie Herring, lead editor of the special report, said at a press conference announcing the findings.
Averaged across the past eight years, about 73% of published studies have found a role for climate change in the events they examined, versus about 27% that didn’t. But it isn’t an even split over time. In the last few years, more papers have pointed to the influence of global warming—about 95% of them these days, Herring noted.
In this year’s report, only one paper failed to find a significant tie to climate change. And even then, the results may have been affected by methodological limitations.
That study, an analysis of an extreme rainfall event in Tasmania, Australia, examined a single day’s unusually heavy precipitation. It caused flash flooding and damage across the city of Hobart in a short time. Such remarkable single-day events are rare in the historical record, meaning there are very few events to compare with one another.
The authors suggest that the small sample size may be one reason they were unable to link the event to climate change. In other words, warming may still have played a role in the event—it’s just difficult to say because of the limited record.
On the other hand, researchers found that extreme floods in the Mid-Atlantic U.S. were up to twice as likely under the influence of climate change. Warming in the Four Corners region contributed to drought and substantially reduced seasonal snowpack. Heat waves in Europe were warmer than they would have been without global warming and many times more likely to occur as a result of climate change. Extreme rain in Japan was 7% heavier because of the country’s warming.
And those are just a few.
Some research groups also identified events that are becoming rarer in a warming world.
For instance, February 2018 saw unusually high precipitation in central and southern Mozambique, Zimbabwe and southern Zambia—a region that scientists expect will become drier as the climate continues to change. A study in this year’s special report found that this sort of heavy rainfall event is already up to 37% less likely to occur because of the influence of climate change.
More warming, better science
The special bulletin doesn’t include every attribution study conducted each year. Other studies are published in other journals, continually widening the body of literature over time.
But the bulletin’s annual collection does provide a window into how both the science and the climate are changing over time.
There are two reasons the report may be finding more links to climate change as time goes on, experts suggest. One reason is that the influence of global warming is simply growing stronger.
Two years ago, studies in the bulletin found—for the first time ever—that some events would not have been possible without the influence of climate change. The same was true for some studies in last year’s report. For instance, a 2017 marine heat wave off the coast of Australia was found to have been “virtually impossible” in a world without climate change.
Most attribution studies find that a given event was simply made more likely to occur, or perhaps more intense, by the influence of global warming. To some experts, discovering entirely novel events in today’s warming climate is a reminder that the Earth is moving into unprecedented territory.
At the same time, scientists may also be finding more links to climate change because their research is growing more advanced.
Attribution science has been one of the fastest growing fields of climate science since it took off about 15 years ago. In its early days, attribution studies were mainly limited to simple, easy-to-model events, like heat waves.
In recent years, though, scientists have been able to tackle substantially more complex phenomena, like hurricanes and wildfires. And they’re getting better—and faster—at detecting the influence of human activities.
“What we’re seeing now is papers that embrace an incredible range of phenomena,” said Jeff Rosenfeld, editor-in-chief of the Bulletin of the American Meteorological Society. “And that is really a testament to the amount of work that is going into developing this field so rapidly.”
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news a twww.eenews.net.