Biblical prophets foretold whirlwinds, but reliable hurricane forecasts elude even modern scientists, notes Andrew Robinson
The concluding words of US scientist Kerry Emanuel's just-published book about hurricanes - which went to press at the end of 2004 - have turned out to be prophetic in the aftermath of Hurricane Katrina. "While global warming may eventually have a noticeable effect on hurricane activity, there is no evidence of a warming-induced trend in hurricanes so far, and while we focus on the distant future we ignore the peril on our doorstep." That is, the peril inherent in massive coastal development. Emanuel notes: "A succession of directors of the National Hurricane Center have for decades travelled the East and Gulf coasts of the United States and testified to Congress, warning that the upswing in coastal population, coupled with inadequate construction, was setting us up for disaster. They have been largely ignored. Federal and state policies on such matters as flood insurance and disaster relief continue to encourage development in flood- and hurricane-prone regions, forcing all taxpayers to subsidise the risks undertaken by a few. In this respect, we could not differ more from the [ancient] Mayans, who learned to build their cities well inland."
The current director of the National Hurricane Center, Max Mayfield, echoes Emanuel's comment on the back jacket: "Today's coastal development, along with hurricane amnesia, places modern man on a collision course with catastrophe if the lessons of history are ignored."
Emanuel even offers a specific "nightmare scenario" about New Orleans in the chapter on "Forecasting hurricanes". "A small, rapidly moving hurricane intensifies as it moves northward in the Gulf of Mexico. Its present course will take it ashore along the Alabama-Mississippi coastline, but a last-minute veer to the left could bring it directly into downtown New Orleans. Much of that city is below sea level and relies on pumps to keep the water out. A strong storm surge coupled with heavy rain could overwhelm the pumps and submerge most residences and one-story buildings. Evacuate, or trust the forecast?"
The particular difficulty with forecasting hurricanes, as compared with other great forces of nature, is that they are neither effectively unpredictable like earthquakes and lightning, nor slow-moving enough to permit a planned response like river floods and droughts, but lie somewhere between these extremes. Their paths can nowadays be tracked in detail and their wind speeds and humidity monitored by satellites and aircraft, but hurricanes can still behave like mavericks. At short notice they can change direction and devastate a major city rather than hitting a nearby, relatively uninhabited coastline, or they can suddenly intensify as a result of unanticipated interactions with air pressure, heat and moisture in the atmosphere, in the ocean and on land.
Emanuel, a professor of earth, atmospheric and planetary science at the Massachusetts Institute of Technology and one of the world's leading hurricane researchers, does not try to conceal how little is known about hurricanes; in fact, he lays out the scientific uncertainties for a general readership.
About how hurricanes form, for example, he states: "Although some aspects of the transformation of atmospheric disturbances into tropical cyclones are relatively well understood, the general problem of tropical cyclogenesis remains I one of the great mysteries of the tropical atmosphere." Why do a few of the regular series of atmospheric waves transmitted from the Sahara Desert to the Atlantic Ocean become hurricanes while the vast majority do not? And about the much-debated effect of global warming on hurricanes, Emanuel is distinctly cautious: "Although there is considerable evidence that hurricanes would be more intense in a warmer climate, the question of how frequently they might occur remains largely unanswered. Complex computer models of the global climate system now resolve the atmosphere well enough to produce storms that behave like tropical cyclones, but their resolution is still too coarse to capture the structure of the eye and eyewall, and consequently the modelled storms are too weak." When different computer models are used to predict the effect of doubled carbon dioxide concentration in the atmosphere, some of them predict an increase in storm frequency, while others predict a decrease.
"Science has not progressed far enough to allow us to say anything meaningful about how hurricane frequency might change in response to global warming." In an article published in Nature a few weeks before Katrina hit the US, Emanuel repeated this view.
The emphasis of this book - like Howard Bluestein's comparable book, Tornado Alley: Monster Storms of the Great Plains (also published by Oxford University Press) - is, as it should be, on science. But the scientific explanations make fewer concessions to the non-scientific reader than might have been expected. However, the excellent photographs and satellite images of hurricanes and their dramatic impact, and the vivid and copious diagrams, will help such readers over the difficult patches (despite some errors in the labels and captions, which should have been edited to fit the diagrams and the main text precisely). Anyone wanting to know the current state of our scientific understanding of hurricanes should get hold of this attractively produced book, provided they are willing to make some intellectual effort - anecdotal it is not, with little about the personalities behind hurricane research. Overall, Divine Wind is the best introduction to hurricanes that I have come across, definitely more readable than Roger Pielke's Hurricanes: Their Nature and Impact on Society (1998).
Interleaved between the scientific chapters are chapters on historic hurricanes, ranging from the typhoons that scotched Kublai Khan's attempt to invade Japan in 14 and again in 1281 - leading to the Japanese name for typhoons, kamikaze , the "divine wind" - to the massively expensive Hurricane Andrew disaster in Florida in August 1992, which was said to have been a factor in the election defeat of President George H. W. Bush, as a result of the federal Government's slow and disorganised response to the catastrophe. There are also many paintings of big storms by well-known artists such as J. M. W. Turner and Winslow Homer and by lesser-known modern artists, and numerous quotations from literature, classic and not so classic.
While the accounts of past hurricanes are generally of great interest, if somewhat repetitious en masse, the paintings and literary quotations should have been pruned. Two or three paintings of storm-tossed sailing ships would have been enough, and while Shakespeare's The Tempest , Conrad's Typhoon , Shelley's poetry and the writings of some others such as Emily Dickinson and Lafcadio Hearn are worth citing at length, much of the quoted poetry should have been buried at sea. On the whole, hurricanes have not stimulated artists and writers to create their best work. Who bothers now with John Ford's 1937 film The Hurricane , which takes up a whole page in the book with a cheesy movie poster, as compared with his classic Westerns?
It is not easy to convey the power of hurricanes in words (or even moving images). Perhaps concrete details work better than heavy-duty verbs and adjectives. This is from the autobiography of the US Admiral William F. "Bull" Halsey, whose Third Fleet was badly mauled by typhoons in the western Pacific Ocean in 1944-45. "The rain and the scud are blinding; they drive you flat-out, until you can't tell the ocean from the air. At broad noon I couldn't see the bow of my ship, 350 feet from the bridge. The New Jersey once was hit by a 5-inch shell without my feeling the impact; the Missouri , her sister, had a kamikaze crash on her main deck and repaired the only damage with a paintbrush; yet this typhoon tossed our enormous ship as if she were a canoe. Our chairs, tables and all loose gear had to be double-lashed; we ourselves were buffeted from one bulkhead to another; we could not hear our own voices above the uproar." As Emanuel himself remarks: "The average hurricane at sea precipitates about one trillion gallons of rainwater per day, about triple the rate of freshwater consumption in the United States in 1995." That really is an awesome statistic.
No wonder the Bible was preoccupied with such almighty forces, though the word hurricane itself is not mentioned there; it comes from the New World, possibly from Hurakan, a storm god of the Maya, who were regularly afflicted by hurricanes. Emanuel notes various occasions when hurricanes may have changed the course of great events. Apart from Kublai Khan's two failed invasions of Japan in the 13th century, there is the hurricane that may have prevented the French from wresting control of Florida from the Spanish in the 16th century, the terrible hurricanes of 1780 that destroyed the economy of the Caribbean, and the appalling cyclone in East Pakistan in 1970 (with at least 300,000 deaths, like the 2004 Asian tsunami), callously ignored by the government in West Pakistan, which probably gave a final shove to the independence struggle that gave birth to Bangladesh the following year.
Will the drowning of New Orleans by Hurricane Katrina in 2005 have any lasting effect on the history of the US? Compared with the terrorist attacks of September 11, 2001, the impact will surely be less - except on the insurance industry and Emanuel's own field of hurricane research, which will undoubtedly receive a financial boost. But if the Republicans were to be defeated at the next national election, the Bush (Junior) Administration's inept and scientifically illiterate handling of the Katrina catastrophe would be likely to have played a significant role.
"For they have sown the wind, and they shall reap the whirlwind," as Divine Wind quotes from the book of the Old Testament prophet Hosea.
Andrew Robinson, literary editor of The Times Higher , is the author of Earthshock: Hurricanes, Volcanoes, Earthquakes, Tornadoes and Other Forces of Nature .
Divine Wind: The History and Science of Hurricanes
Author - Kerry Emanuel
Publisher - Oxford University Press
Pages - 285
Price - £26.99
ISBN - 0 19 514941 6