Let’s make the world storm-proof

Chris Mooney has followed up his attack on the Bush administration’s scientific record with a more personal examination of hurricanes (1). Storm World was written in response to Katrina, the category 3 hurricane that hit New Orleans in 2005 leading to the breach of the levee and the subsequent flooding of the city with around 1,700 deaths and material costs generally expected to exceed $100billion (2). Amongst the homes that were eventually destroyed was that of Mooney’s mother.

Mooney begins with a fascinating account of how our understanding of hurricanes has developed. The first suggestion that hurricanes rotated came from the amateur weather researcher, William Redfield, who ingeniously examined the destruction left by the 1821 Norfolk and Long Island Hurricane. Shortly after the hurricane, Redfield followed the destruction by foot and documented that trees felled by the hurricane made a pattern that could best be explained by a rotating mass of air (3).

However, the so-called ‘Storm King’, James Pollard Espy, rejected Redfield’s ideas as ‘bunkum’. Espy argued that hurricanes were caused by thermodynamic changes dependent upon the capture and release of heat as water molecules rise. In essence, air that is warmed by the sun rises, carrying the heat and water vapour with it. As the air rises the pressure on that section of air drops and the air expands and cools so that the water vapour condenses into droplets that become clouds. Espy’s account viewed the formation of thunder clouds and storms as due to a raging rise and dissipation of heat somewhat like in a chimney; there was no possibility of rotation.

Perhaps inevitably a major spat ensued between Redfield and Espy, who were eventually shown to be both right. Thunderclouds do form, at least in part, in the way described by Espy, and hurricanes are gigantic rotating thunderclouds. The rotation is caused by the spin of the Earth, a fact that was recognised within Redfield’s lifetime, but, tragically, Redfield died without ever becoming aware of it (4). Espy died in 1860 still refusing to accept that storms could rotate, despite being aware of the evidence that a rotating Earth can create a rotating cloud.

Between them, Espy and Redfield lay the ground for a new generation of hurricane scientists, including Herbie Riehl, whose observations from the inside of hurricanes, beginning after the Second World War, led him to recognise that condensation energy alone could not be driving intense hurricane activity. Eventually, Riehl was led to the idea that hurricanes derive most of their energy from ocean heat that provides a constant source of warm, humid air. Thus Riehl provided the first connection between hurricane activity and the warming of the oceans via the emission of greenhouse gases.

Mooney explains that the modern discussion of hurricanes and their relation to global warming mirrors that of the nineteenth century. On the one hand is William (Bill) Gray, a student of Riehl who shot to fame by unveiling the first Atlantic seasonal hurricane forecasting system in 1984, and prides himself on his ability to crunch data and observe patterns, rather like Redfield. On the other hand are scientists like Kerry Emanuel, who rely on theoretical insight and computer modelling to provide an understanding of the weather that can lead to better predictions of future storm activity. Interestingly, both camps appear to agree that warming has occurred and both agree that warming will increase the frequency and intensity of hurricanes. They disagree, profoundly, on what is causing the current warming and how long it will last. Gray believes the warming is somehow related to the thermohaline cycle (5), while almost everyone else believes the warming is due to CO2 emissions. Gray maintains that the warming will soon reverse, as the thermohaline cycle changes, while his opponents believe that what warming has occurred will be at least maintained and will continue to increase as CO2 continues to be released.

Mooney does well to treat Gray’s opposition to the consensus on global warming with proper respect, despite Gray’s clearly eccentric views and often gross dismissal of his fellow scientists. It would be easy to dismiss Gray out of hand, forgetting that he pioneered the science of hurricane forecasting and has trained a vast number of younger leading hurricane specialists, many of whom now disagree with him. Science depends upon conviction and scepticism much more than consensus; it is grossly unfortunate to dismiss Gray’s contribution as heretical. There are plenty of unknowns that Gray rightly draws attention to: the effects of clouds and ocean spray, stabilisation from warming at upper levels, the influence of the thermohaline circulation, and the effect of hurricanes themselves pulling up masses of cooler water. Unfortunately, however, Gray’s basic objection to the global warming consensus – that we can’t possibly understand the weather, it’s too complicated and difficult – is simply unconvincing.

The bottom line question out of all this is: Are hurricanes getting worse because of global warming or not? Mooney is not trying to be catastrophic and self-consciously avoids hyperbole. ‘Certainly’, he says early in his book, ‘[this work] is no polemic, no work of alarmism… our scientific understanding of the hurricane-climate relationship remains too incomplete to justify such an approach.’ Towards the end of his book, the picture that Mooney paints is fairly mundane. In the Atlantic, at least, global warming is likely increasing the intensity, and probably frequency, of hurricanes. More hurricanes and hurricanes of increased intensity is a problem for those who live in the paths of hurricanes, but these problems are hardly new and need not be apocalyptic. The category 4 Galveston Hurricane of 1900 killed between 6,000 and 12,000 people, but modern construction and evacuation options should prevent that scale of death in modern Galveston. In fact, a seawall was built in the aftermath of 1900 and dredged sand was used to elevate the city. A category 3 hurricane that hit Galveston in 1915 killed 275 people, a massive reduction from the 1900 hurricane.

In contrast, a 1970 six-metre storm surge caused by a tropical cyclone equivalent to a category 3 hurricane killed some 300,000 to 500,000 people in East Pakistan (now Bangladesh). A cyclone preparedness programme was put in place to warn people of future cyclones but, unlike Galveston, no major sea defences or cyclone-proof homes and bridges were built. In 1991, another intense cyclone with a six-metre storm surge hit Bangladesh and killed around 138,000 people.

Regions that can be hit by hurricanes and cyclones will inevitably be hit by hurricanes and cyclones regardless of the influence of global warming. Whether global warming really is increasing the intensity and incidence of such dramatic weather events, and it seems a fair bet that it is, these weather events fluctuate widely due to many factors that remain to be understood and are a long way from being controlled. Until we can control the weather, defences and evacuation plans can be engineered for the people who choose to live in vulnerable areas and, if necessary, people can permanently relocate.

It is important to recognise that what to do about hurricanes is a social rather than scientific question. It is one thing for scientists to draw attention towards a growing problem such as the potential for more intense and frequent hurricanes due to global warming. It is quite another to tell democratically elected governments how to manage energy policy and city defences in the light of that evidence. Mooney considers the role of science in political decision-making far too uncritically as a choice between ‘sound science’, which emphasises a very high burden of proof before scientific information serves as the basis for significant political action, and the ‘precautionary principle’, which asserts that we cannot wait for all the evidence to come in before we respond.

Both sound science and the precautionary principle fail to provide any resolution to the question of political action. An insistence on a very high burden of proof will mean waiting until something happens and then it is too late. On the other hand, taking action before it is necessary wastes resources. Wisdom lies in knowing when action is necessary, and that is a political decision not a scientific one.

Mooney laments that scientists are too enamoured to the peer-reviewed literature and too reluctant to make general political observations and recommendations. He wants scientists to ‘stop being only scientists, and realise that they must be communicators – and leaders, and examples – as well’. Following these recommendations will be disastrous for both science and politics.

Good scientists know that their data and observations can be misleading. A single line of investigation is rarely correct absolutely, which is why peer review is so important. It acts as a system of checks and balances to maintain an even keel towards the truth. Scientists respect this process because it generally works and affirms the legitimate nature of science by holding it up to proper scrutiny. Scientists who try to run around this process by appealing directly to the media or politicians undermine the credibility of scientific pursuit. Does Mooney really want scientists delivering their data direct to the media to support their plans for social reorganisation?

Although it might seem entirely sensible for scientists to inform public policy, there is a line between information and policy and between scientists and politicians. Scientists are not democratically elected; they have no popular mandate for deciding what Florida should do about hurricanes or how Bangladesh should organise building policy. However well-intentioned, shifting expertise into a position of authority without electoral support is a form of tyranny. Clearly Mooney does not see it that way, and probably neither do many people. The introduction of science into policy is generally regarded as benign, a well-intentioned and useful process. The aim is to protect life and liberty and not to undermine it. This is disarmingly unlike the tyrannies of the past and so it escapes popular opposition.

The problem, however, is that public and social policy is not something that can be decided by an empirical process that avoids public debate. People can, if they wish, decide to live on the coast in the face of increasing hurricanes. Society can, if it chooses, offset the cost of people being in harm’s way. It is not the job of science to decide what is best for humanity; that is the job of the people. If science, even well intentioned and technically correct science, takes that decision away, then we have tyranny.

Stuart Derbyshire is a senior lecturer in the School of Psychology, University of Birmingham. He is speaking at the Battle of Ideas festival in London on 27-28 October.

Storm World by Chris Mooney is published by Harcourt Trade. (Buy this book from Amazon(UK).)

1. The Republican War on Science, Chris Mooney, Basic Books, 2006

2. A category 3 hurricane delivers winds between 178-209 km/hr and generates a storm surge of 2.7 – 3.6m above normal.

3. Trees felled in North West Connecticut pointed towards the south east, whereas those in central Connecticut pointed north west. Redfield correctly concluded that only a whirlwind could have created such a pattern.

4. The French scientist, Gaspard-Gustave de Coriolis, noted in 1835 that because of the planet’s rotation, objects in motion are subject to a certain ‘force’ that deflects their trajectory, a force now known as the Coriolis force. It was William Ferrel, a Pennyslvanian school teacher, who recognized that the Coriolis force could explain the rotation of hurricanes and their counterclockwise rotation in the north and clockwise rotation in the south. Incidentally, contrary to popular belief, the Coriolis force is not sufficient to alter the rotation of water down the plughole, although it can influence wind and ocean currents, at the level of the bathroom sink the effect is too small.

5. The thermohaline circulation refers to the movement of sea water caused by changes in temperature (‘thermo’) and saltiness (‘haline’). As North Atlantic water flows north, some of it evaporates while the rest grows colder. The remaining water is thus more salty, dense and heavy. These dense waters sink and flow south again pulling warm water northwards like a giant conveyor belt. Gray argues that alterations in this circulation cause global warming and cooling.