Sandy’s climate context

Why generalizing about extreme weather helps no one

It should come as no surprise that as Hurricane Sandy spiraled up the eastern seaboard, a variety of media outlets sought to explain the so-called super storm’s relationship to climate change. A few did well, but generalizations about extreme weather continue to mar this type of coverage.

Take Rebecca Leber’s attempt to bash the press for ignoring climate change at Climate Progress. “Despite the hysteria surrounding Hurricane Sandy,” she wrote, “not one major newspaper has reported the scientifically established link that carbon pollution fuels more extreme weather.”

That assertion about an established link is misleading. In reality, climate change fuels some extreme weather in some places, and the links are not very well understood. As Gavin Schmidt, a climate modeler and NASA’s Goddard Institute for Space Studies, put it in a blog post for last year:

Not all extremes are the same. Discussions of ‘changes in extremes’ in general without specifying exactly what is being discussed are meaningless. A tornado is an extreme event, but one whose causes, sensitivity to change and impacts have nothing to do with those related to an ice storm, or a heat wave or cold air outbreak or a drought.

There is no theory or result that indicates that climate change increases extremes in general. This is a corollary of the previous statement - each kind of extreme needs to be looked at specifically - and often regionally as well.

Even some of the best reporters continue to generalize extremes, despite these crystal-clear warnings that they shouldn’t. In a post for The New Yorker, for instance, Elizabeth Kolbert wrote:

As with any particular “weather-related loss event,” it’s impossible to attribute Sandy to climate change. However, it is possible to say that the storm fits the general pattern in North America, and indeed around the world, toward more extreme weather, a pattern that, increasingly, can be attributed to climate change.

Kolbert not only misleads readers to believe that climate change increases all extremes everywhere, but after asserting that Hurricane Sandy “fits” this “general pattern,” she cites a recent paper about heat waves to support her claim. It’s a classic bait-and-switch and totally irresponsible since the dynamics of heat waves are very different from those of hurricanes.

Adam Frank did much better in a post for NPR where he eschewed the temptation to generalize about extremes and placed tropical cyclones in their proper context.

“There is a hierarchy of weather events which scientists feel they understand well enough for establishing climate change links,” he wrote. “Global temperature rises and extreme heat rank high on that list, but hurricanes rank low.”

CNN apparently banned use of the term “Frankenstorm” to describe Sandy, but it’s actually a good nickname because the first-order explanation for its strength was an unusual confluence of different weather systems. As the AP’s Seth Borenstein explained, the hurricane, a western cold front, frigid air flowing down from the Arctic, and extreme high tides converged to create a mostly natural disaster.

Climate change also plays a part, but it’s a complicated role indeed (see Andrew Revkin’s post at The New York Times for details). In a widely quoted paper published in March, Kevin Trenberth, a scientist in the Climate Analysis Section at the National Center for Atmospheric Research wrote:

The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.

Saying that climate change affects all weather is different than saying that climate change increases extremes in general, though. As Trenberth put it, “It is when natural variability and climate change develop in the same direction that records get broken.” With Hurricane Sandy, he wrote in a guest post for Climate Progress, climate change “contributed” (on the order of 5 to 10 percent) to unusually high ocean temperatures in the Atlantic, which meant more moisture in the atmosphere and thus more rainfall. In other words, natural variability provided the “optimal conditions” for a huge storm, which were “enhanced by global warming.”

In an article by The Huffington Post’s Tom Zeller, Jr., Trenberth said that storms like Sandy are the “new normal,” but that’s not exactly how the Intergovernmental Panel on Climate Change (IPCC), the world’s foremost authority on the subject, sees it. In a special report on extreme weather published this summer, it said:

There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities.

That’s not to say that events like Sandy won’t become the new normal eventually. According to the special report, there’s already been an increase in the number of heavy precipitation events in some regions. There’s also been a decrease in some regions, but it’s “likely” that there are more in the former category, and “there is medium confidence that anthropogenic influences have contributed to intensification of extreme precipitation at the global scale.” As for the future (and it’s important to note that the IPCC distinguishes between heavy rainfall events and hurricanes, which are related but distinct):

It is likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy falls will increase in the 21st century over many areas of the globe. This is particularly the case in the high latitudes and tropical regions, and in winter in the northern mid-latitudes. Heavy rainfalls associated with tropical cyclones are likely to increase with continued warming. There is medium confidence that, in some regions, increases in heavy precipitation will occur despite projected decreases in total precipitation in those regions.

Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged.

There is medium confidence that there will be a reduction in the number of extratropical cyclones averaged over each hemisphere. While there is low confidence in the detailed geographical projections of extratropical cyclone activity, there is medium confidence in a projected poleward shift of extratropical storm tracks.

That’s a lot to chew on, obviously, but the point is that reporters who generalize about climate change and extremes do so at their own peril, as do those who seek easy answers about any individual weather event. Boing Boing’s Maggie Koerth-Baker described the situation perfectly in her post about Sandy:

Part of the problem here is that we’re expecting science to operate on the scale of American media news cycles, which doesn’t really work. We want to talk about this while the storm is raging or, barring that, at least immediately afterwards. But scientists aren’t really going to have anything particularly deep to say about this specific storm for months, if not years. During that time, data will be analyzed and compared, and other events will happen, and that’s really the stuff that we need in order to say much of anything other than, “We don’t know for certain.” In some ways, expecting anything else means forcing scientists to speculate and extrapolate in ways they aren’t usually comfortable with and that aren’t a terribly great way to understand the big picture.

Indeed, as The Washington Post’s Brad Plumer and Climate Central’s Michael Lemonick both explained, regardless of whether or not climate change leads to more frequent or intense hurricanes, global warming is causing sea-level rise that will exacerbate the storm surge from any cyclone that comes along—and it’s those kind of details that get lost in generalizations about extreme weather events.

Has America ever needed a media watchdog more than now? Help us by joining CJR today.

Curtis Brainard writes on science and environment reporting. Follow him on Twitter @cbrainard. Tags: , , , , ,