Tracking the Truth About Tornadoes
December 5, 2013
Richard Muller is a Berkeley Physics prof and would-be media star. Dr Muller got some attention a few years ago for some viral lectures slandering climate science and scientists,and whored himself on the Glenn Beck/Fox News circuit. Then he wangled a bunch of money from the Koch brothers to study the temp record. Then he found out that global temps were in fact, rising.
Richard Muller is now a media star as the “former climate skeptic scientist who now believes in climate change”.
So, following the recent rash of tornado activity, Muller writes in the NYTimes claiming that, paradoxically, there will be fewer tornadoes in a warming world, and was promptly blown out of the water by actual meteorologists and scientists who really know something about the problem.
Presumably he will now become more famous and sought-after as the “scientist who formerly thought there would be fewer tornadoes in a warming world, but has now been blown out of the water by actual meteorologists and scientists who really know something about the problem”
We can safely predict that even more “serious” journalists will now continue to seek him out, flatter him, and help him sell books.
Failing up. It’s a strategy. It works.
Muller, who lacks any training or expertise in atmospheric science, is more than happy to promote with great confidence the unsupportable claim that global warming will actually decrease tornado activity. His evidence for this? The false claim that the historical data demonstrate a decreasing trend in past decades.
Actual atmospheric scientists know that the historical observations are too sketchy and unreliable to decide one way or another as to whether tornadoes are increasing or not (see this excellent discussion by weather expert Jeff Masters of The Weather Underground).
So one is essentially left with the physical reasoning I outlined above. You would think that a physicist would know how to do some physical reasoning. And sadly, in Muller’s case, you would apparently be wrong.
To allow Muller to so thoroughly mislead their readers, not once, but twice in the space of as many months, is deeply irresponsible of theTimes. So why might it be that the New York Times is so enamored with Muller, a retired physicist with no training in atmospheric or climate science, when it comes to the matter of climate change?
Now, a group of actual tornado and convective storm experts have weighed in. Muller not coming off so well.
Twisters returned to the national spotlight after a Nov. 17 outbreak viciously tore through 12 states, leaving eight people dead.
Research data show that climate change caused by human behavior is fueling more frequent and intense weather, such as extreme precipitation and heat waves — so it’s only natural to wonder if this applies to tornadoes, too. Scientists need more data and time to fully address that connection.
For instance, University of California, Berkeley, professor Richard Muller argued in a recent New York Times opinion piece that “the scientific evidence shows that strong to violent tornadoes have actually been decreasing for the past 58 years, and it is possible that the explanation lies with global warming.”
The honest “truth” is that no one knows what effect global warming is having on tornado intensity. Tornado records are not accurate enough to tell whether tornado intensity has changed over time.
Although it is a bit of an exaggeration to say, “backyard dust devils are reported,” Muller notes — correctly— that climate change is not responsible for the dramatic rise in annual tornadoes since 1950. Rather, the larger numbers come from improved detection and reporting of weak tornadoes, particularly EF0 tornadoes, where “EF” refers to the enhanced-Fujita scale used by the National Weather Service (NWS).
However, Muller then uses the record of severe tornadoes — those rated EF3 to EF5 and responsible for the most extreme damage and casualties — to reach the following conclusion: “One thing is clear … The number of severe tornadoes has gone down. That is not a scientific hypothesis, but a scientific conclusion based on observation. Regardless of the limitations of climate theory, we can take some comfort in that fact.”
His confident claim is based on raw U.S. National Oceanic and Atmospheric Administration (NOAA) records showing an apparent decline in EF3 to EF5 tornado reports in the past 58 years. Unfortunately, it illustrates a lack of understanding of how those reports have been developed, and the changes in the process over time. Scientific conclusions must be based on reliable observations, not just any observations.
Ironically, the reason Muller says one shouldn’t attribute the increase in weak (and therefore total) tornado reports to climate change is likely the same reason the intensity of tornadoes has appeared to decline:reporting has not been consistent over the period the tornado records span.
The meteorological community knows very well that early official records systematically rated tornadoes stronger than those in the 1980s and 1990s — that is, tornadoes were awarded higher EF-ratings in those decades than they would have received in more recent times.
Tornadoes occurring prior to the mid-1970s — when the NWS adopted the enhanced Fujita scale — received ratings retrospectively by meteorology students who relied on qualitative damage descriptions in newspaper archives. This effectively “inflated the grades” of those tornadoes because the later ratings came only after considerable in-person scrutiny of the damage, often by engineers who considered not just the damage but also the quality of the construction of damaged structures. The evidence for the overrating of earlier tornadoes includes the fact that environments and damage paths of many strong tornadoes in that retrospective era shared characteristics with weaker tornadoes from later years.
Considerable evidence uncovered in the last decade suggests that previous tornadoes actually were underrated compared to the 1980s and 1990s.
One factor contributing to those ratings was a 2003 policy that required a special team of experts to evaluate the damage of the strongest tornadoes. In an unforeseen consequence, local NWS offices had a tendency to assign lower initial ratings, eliminating the expense and complexity of involving external evaluators. In addition, concerns about construction practices from the engineering community placed additional emphasis on poor construction by damage assessors from the NWS, leading to lower ratings.
Also, in another complication in assessing long-term tornado intensity trends, the “damage indicators” used to rate tornadoes recently have changed with the adoption of the EF scale, making it dubious to compare tornadoes of the past with those of the present.
Recently, truck-borne Doppler radar observations of tornadoes identified a number of cases in which the radar-measured winds are considerably faster than the official NWS rating implies. For example, the winds measured by these radars in last May’s 2.6-mile-wide tornado near El Reno, Okla., topped 280 mph, which would have placed it well into the EF5 range (200+ mph). The official NWS rating based on the available damage indicators, however, was EF3 (136–165 mph).
Finally, Muller’s simple analysis of tornado reports does not address possible changes in the seasonality and/or regional nature of tornado occurrence. In fact, the latest climate-model experiments agree that further global warming is likely to increase the likelihood of conditions favorable to the severe thunderstorms that produce tornadoes in the spring and autumn. Although these climate models do not resolve tornadoes, they do predict an increase in the ingredients responsible for past tornadoes.
Paul Markowski, professor of meteorology at Penn State University, was a leader of the recent Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) and 2013 recipient of the National Weather Association’s Fujita Award for his research on tornado formation.
Harold Brooks is a senior research scientist at NOAA’s National Severe Storms Laboratory, has authored numerous scientific papers on tornado climatology, and was a contributing author on the recent Intergovernmental Panel on Climate Change’s Fifth Assessment Report.
Yvette Richardson, associate professor of meteorology at Penn State University, is a Councilor of the American Meteorological Society and was a leader of the recent Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2).
Robert J. Trapp, professor of atmospheric science at Purdue University, has published several articles on the topic of severe thunderstorms and climate change.
John Allen, postdoctoral research scientist at the International Research Institute for Climate and Society at Columbia University, has authored several recent journal articles on relationships between the climate system and severe thunderstorms.
Noah Diffenbaugh is an associate professor in the School of Earth Sciences and the Woods Institute for the Environment at Stanford University. He is currently a Lead Author for the Intergovernmental Panel on Climate Change.
Abstract from Diffenbaugh et al, 2013, “Robust Increases in Severe Thunderstorms Environments in Response to Greenhouse Forcing”:
Although severe thunderstorms are one of the primary causes of catastrophic loss in the United States, their response to elevated greenhouse forcing has remained a prominent source of uncertainty for climate change impacts assessment. We find that the Coupled Model Intercomparison Project, Phase 5, global climate model ensemble indicates robust increases in the occurrence of severe thunderstorm environments over the eastern United States in response to further global warming. For spring and autumn, these robust increases emerge before mean global warming of 2 °C above the preindustrial baseline. We also find that days with high convective available potential energy (CAPE) and strong low-level wind shear increase in occurrence, suggesting an increasing likeli- hood of atmospheric conditions that contribute to the most severe events, including tornadoes. In contrast, whereas expected decreases in mean wind shear have been used to argue for a negative influ- ence of global warming on severe thunderstorms, we find that decreases in shear are in fact concentrated in days with low CAPE and therefore do not decrease the total occurrence of severe environments. Further, we find that the shift toward high CAPE is most concentrated in days with low convective inhibition, increasing the occurrence of high-CAPE/low-convective inhibition days. The fact that the projected increases in severe environments are robust across a suite of climate models, emerge in response to relatively moderate global warming, and result from robust physical changes suggests that continued increases in greenhouse forcing are likely to in- crease severe thunderstorm occurrence, thereby increasing the risk of thunderstorm-related damage.
The analysis carved the United States into boxes that were roughly 60 miles on a side and assessed the climate conditions that could emerge over the next century. The analysis showed the biggest changes occurring in the spring season, with each box in the central United States experiencing about two-and-a-half additional storm days per spring by the late 21st century.
The researchers also reported that sustained global warming is likely to cause robust increases in storm days over large areas of the eastern United States not only in spring but also in winter and autumn. While the summer season also showed increases over the region as a whole, those increases were the least robust within the region and across the different climate models.
An additional few days of severe storm conditions might not seem like a large change, but Diffenbaugh emphasized that the projected increases are in fact substantial compared to the frequency of occurrence in the current climate.
“We are looking at the conditions that produce severe events, which are relatively rare at present,” Diffenbaugh said. “For example, the changes during spring represent an increase of about 40 percent over the eastern U.S. by the late 21st century.”
Diffenbaugh also emphasized even a single severe storm can cause very high levels of damage.
“The severe thunderstorms we experience now can result in very high economic losses,” Diffenbaugh said. “Sadly, we have many examples of cases where a single storm has had disastrous impact. So a 25 or 30 percent increase in the annual occurrence represents a substantial increase in the overall risk.”
There has been a lively conversation on severe storm/climate change science in the wake of Typhoon Haiyan and the November tornado outbreak. Certain key ideas seem to be bubbling to the top, and this will probably be the subject of a video soon after I return from AGU.