Hurricanes: Why Worry
As a child, Kerry Emanuel was captivated by thunderstorms–planting himself by windows to watch them. He has followed that meteorological passion through decades of research and teaching at the Massachusetts Institute of Technology to become what one science reporter calls “arguably the world’s top expert on hurricanes.”
Most hurricane specialists are weather forecasters, tracking the path of tropical cyclones (the scientific term for storms with sustained wind speeds in excess of 74 mph). Far fewer engage in the sort of research Emanuel does–looking at how climate change may affect hurricane intensity and frequency.
Emanuel’s fascination with hurricanes extends well beyond modeling exercises in the lab. He wrote a book, Divine Wind, that weaves together meteorological science, historical storm accounts, artistic renditions and poetic accounts of what William Cullen Bryant called “the shadowy tempest that sweeps through space/A whirling ocean that fills the wall/Of the crystal heaven, and buries all.”
Emanuel met with me recently, overlooking the Maine harbor where his meteorological training began with childhood sailing lessons, to talk about storm forecasting, the chasm between science and policy, and how hurricanes offer yet another reason (as if we needed more) to rein in climate change.
“No natural phenomenon poses a greater challenge to forecasters than the hurricane,” Emanuel holds; some like earthquakes elude forecasting altogether while others are relatively predictable. Knowledge of hurricanes is always imperfect, Emanuel says, which generates great angst because inevitably there’s “an awful lot riding on human judgment.”
Asked about technological advances in forecasting, Emanuel winds the clock back to Sept. 21, 1938 – an overcast day in New England with gloomy newspaper headlines about growing tensions in Europe. The day’s forecast, buried in fine print, predicted “Rain, probably heavy today and tomorrow, cooler.” With no public warning, the Great Hurricane of 1938 slammed into Long Island and New England that day, killing 680 people and racking up damages that would total billions in today’s dollars.
At that time, there were few weather balloons, no Hurricane Hunter military flight crews sent into storms (both began in the ’40s), and no satellites (first launched in the ’60s and ’70s). Better computer simulations, an unsung advance, further refined hurricane forecasting in the mid-1990s.
Thanks to these innovations, Emanuel explains, a four-day hurricane forecast today is likely to be as accurate as a one-day forecast was 35 years ago.
Hurricane forecasts measured in days are life-saving; those measured in months (seasonal forecasts) Emanuel politely calls “inadvertently misleading.” The number of storms forecast for a given season has little bearing on how many make landfall and wreak havoc.
Seasonal forecasts that promise few tropical cyclones may engender a false sense of assurance. Hurricane Andrew, the most costly tropical cyclone to date when it struck Florida in 1992, occurred during one of the quietest hurricane seasons on record.
Emanuel would like to see the whole warning system for hurricanes revisited. The Saffir-Simpson scale that classifies hurricanes based on sustained wind speeds into Categories 1 through 5 is neither useful for public outreach nor especially scientific. (Emanuel jokes that scientists would never settle for something so simplistic as a 1-5 rating system.)
Currently, hurricanes can be downgraded and evacuations canceled, as happened temporarily with Superstorm Sandy, when storm winds drop below an arbitrary threshold.
Emanuel envisions a much simpler means for communicating a hurricane’s hazards – such as a “code yellow/code red” alert – based on projections for wind, rain (flooding) and storm surge. This change could reduce what he calls “the tension between public safety and commerce,” making it easier for officials to issue and stand by warnings – even in the face of outcries and threatened lawsuits from those concerned that hurricane warnings will hurt business.
More regrettable still, Emanuel believes, are the multiple policies that subsidize people (through insurance and the structuring of federal disaster relief) to live in flood-prone areas, putting “high-value, low-strength structures in harm’s way.” (Interestingly, a new report by the Congressional Budget Office, Potential Increases in Hurricane Damage in the United States: Implications for the Federal Budget, acknowledges the high societal cost of current practices and suggests reforms in both insurance and disaster relief.)
What’s ironic about the Great Hurricane of 1938, Emanuel observes, is that despite forecasting advances, just as many people might be lost if a similar hurricane struck today due to the intensity of coastal development and the flimsy construction of many modern buildings.
Concerns about flooding – both coastal and inland – will only grow with climate change since warmer air holds (and then releases) greater volumes of water. New England saw intense precipitation events increase by more than 70 percent between 1958 and 2010. Now, hurricanes that can deliver torrential rains may begin dumping even higher volumes.
Climate scientists predict that hurricanes will become more forceful as well, fueled primarily by warmer sea temperatures in the tropics. Since 1980, hurricane power (as measured by sustained wind speeds) has roughly doubled in the North Atlantic.
Most damage is done by Category 3 or higher hurricanes, and recent modeling by Emanuel and others strongly suggests that higher-category storms in the North Atlantic and elsewhere will become more frequent as the climate warms further. Factor in sea-level rise generating greater storm surges, and the scenarios do not look good.
Despite the ominous models, slow progress in reducing greenhouse gas emissions, and political gridlock, Emanuel remains optimistic about tackling climate change–confident that “more and more people, particularly young people, get it.”
© Marina Schauffler, 2016. All Rights Reserved. Column reprints available upon request.