“The Party Line”
The worst Atlantic hurricane season on record still hadn’t ended when the American Geophysical Union held its fall meeting in San Francisco in December 2005. Twelve thousand scientists packed themselves into the Moscone Center, the city’s space-age mall of a conference facility, for lectures on topics such as the massive 2004 Sumatra-Andaman earthquake and the tsunami that it generated, and data beamed from NASA’s Mars rovers and the Cassini spacecraft. Many of the presentations were being given on the center’s upper levels, and security guards had to police the towering escalators just to prevent overcrowding.
MIT hurricane theorist Kerry Emanuel arrived on this scene riding a swell of fame that few researchers ever experience. A short man with striking blue-green eyes and a slightly surprised smile, Emanuel had just seen his latest work featured in a Time magazine cover story and would soon find it rated (along with the work of several colleagues) the top science story of the year by Discover. He was averaging five to ten media calls per week. Later, he would be named one of the hundred “Most Influential People of 2006,” once again by Time. At the American Geophysical Union meeting, Emanuel had been slated to speak following another of Time’s most influential: NASA’s James Hansen, the nation’s best-known climate scientist and the man sometimes dubbed the “father” of global warming.
The science presented at the average American Geophysical Union meeting features a heavy helping of catastrophe. Tornadoes, volcanoes, earthquakes, tsunamis—the proceedings offer a subject roster that Hollywood disaster-movie directors would appreciate. But that December, the cause of destruction at the front of everyone’s mind was the strongest and deadliest storm on Earth, a meteorological monstrosity capable of churning out as much power as all the world’s electricity generators combined: the tropical cyclone, typhoon, or, as we call it in the United States, the hurricane.
Katrina had wiped out New Orleans just a few months earlier.
On the day of Emanuel’s talk—Tuesday, December 6—Hurricane Epsilon whirled on in the North Atlantic some 600 miles southwest of the Azores. The aimless cyclone had already executed a full loop, completely reversing its original westward trajectory, and now began a southwest turn. Epsilon wasn’t a particularly strong storm—its maximum sustained winds peaked at around 85 miles per hour—and it never seriously threatened land. But it was stubborn. Moreover, Epsilon had the distinction of being only the sixth hurricane ever recorded as occurring in the Atlantic during the month of December, as well as the twenty-seventh storm of a seemingly never-ending season—so never-ending, in fact, that forecasters had resorted to Greek letters after pre-assigned storm names—like Katrina, Rita, Wilma—ran out.
At the National Hurricane Center in Miami—a steel-reinforced concrete bunker of a building on the campus of Florida International University that was built to withstand Category 5 hurricanes and whose roof bristles with dishes and antennae—the experts awaited Epsilon’s demise. With it, they hoped, would come the official end to the devastating 2005 season, and more than a few sighs of relief.
Traditionally, the hurricane season in the Atlantic basin—which comprises the North Atlantic, the Caribbean Sea, and the Gulf of Mexico—begins on June 1 and ends on November 30. In 2005, however, nature had already toppled such bookends. And now, despite days of forecasts predicting steady weakening, Epsilon had held on to hurricane strength and even put on a few small bursts of intensification.
“I HAVE RUN OUT OF THINGS TO SAY . . .AND THIS ONE WILL BE SHORT,” wrote Cuban-born forecaster Lixion Avila in an exasperated 4:00 a.m. discussion of the storm’s progress, written in the all-caps and heavily elliptical style that remains the standard for weather communiqués.
“EPSILON APPEARS TO STILL BE A HURRICANE...BUT JUST BARELY,” wrote forecaster Richard Knabb six hours later. “THE END IS IN SIGHT,” echoed forecaster James Franklin at 10 that evening. “IT REALLY REALLY IS.”
By the time Epsilon finally died down—having been for five days a hurricane, a December record—Kerry Emanuel had generated a tempest of his own in San Francisco. Speaking before a crowd of hundreds in one of the largest of the Moscone Center’s high-ceilinged conference rooms, the normally cautious and apolitical scientist fired a shot straight at the bosses of government forecasters like Avila, Knabb, and Franklin.
Earlier in the day, the audience had heard the wiry Midwestern climatologist James Hansen warn that global warming could cause the disintegration of the Greenland and West Antarctic ice sheets, triggering rises in sea level sufficient to inundate many of the globe’s heavily inhabited coastal areas. After a break, Emanuel launched into a seemingly typical scientific talk, constructed out of PowerPoint images rather than paragraphs. He flashed slides demonstrating that although global tropical cyclone numbers do not show any obvious trend up or down—averaging about eighty to ninety per year in the world’s six regularly active ocean basins—storms in the Atlantic and the Northwest Pacific had grown stronger and longer lasting over the past several decades, closely tracking a trend of rising temperatures at the surface of the oceans.
To explain this phenomenon, Emanuel then introduced a series of equations. These probably meant little to the nonscientists in the audience, but to specialists capable of reading the equations as if they were sentences, the message was clear: Increasing hurricane strength is linked to human enhancement of the greenhouse effect.
The Earth’s atmosphere contains certain gases, such as carbon dioxide and water vapor, that have a very important property: They absorb infrared or “longwave” radiation and also emit it in all directions. As a result, these gases play a crucial role in regulating the flux of energy to and from the planet. Even as the sun’s rays heat the Earth’s surface, the Earth also emits radiation in the infrared part of the spectrum, with a longer wavelength than that of visible light. The “greenhouse gases” then absorb some of that outgoing heat radiation (which might otherwise escape into space), warm up, and emit more radiation back down toward the lower atmosphere and the Earth’s surface. In the process, these gases keep our planet much warmer than it would be if it lacked an atmosphere.
Through industrial processes such as smokestack and tailpipe emissions, humans have been steadily increasing the concentration of carbon dioxide and other greenhouse gases in the atmosphere. As a result, we’ve caused additional warming of the Earth’s surface, lower atmosphere, and oceans—and that’s where hurricanes come into the picture. Since these storms draw their power from the energy stored in tropical ocean waters, warmer seas should (everything else being equal) make them stronger.
This hypothesis—that hurricanes would intensify in a warmer world—had been around at least since 1987, published in that year by Emanuel himself. Theoretically based predictions, however, don’t hit you in the gut like hard