What’s floods got to do with it?

As summer comes to an end, we can look back on yet another year of unusual weather. (Yes, every year seems to be unusual.)

The biblical-scale floods across Europe, in which the Elbe River flowing
across Germany rose half a metre higher than its previous 1845 record, and the flood in Putney High Street, London, which closed the cinema for a day, have receded. But the ensuing doom-mongering about global warming is unlikely to abate so quickly.

The European media were quick to blame the floods on anthropogenic-induced (man-made) global warming. They could quote spokespersons like Dr Mojib Latif of the Hamburg Max-Planck Institute in Germany, who warned that extreme weather events would become more common as global temperatures rise. Latif clearly approves of the kind of media attention given to the floods. ‘Until now, many people thought that global climate change was happening elsewhere and would not affect our weather patterns here in Europe’, he said (1).

At home in the UK, Dr Julian Salt, an advisor to the insurance industry, wrote a letter to one national newspaper warning that rising insurance claims from floods would make the insurance market ‘unsustainable’ (2). Right on cue, UK prime minister Tony Blair, speaking in Mozambique on 1 September 2002, called for radical cuts in greenhouse gas emissions, as a measure to reduce global warming.

But while you would not realise this from reading the UK press, European scientists were actually more circumspect about the relationship between global warming and the recent floods. For instance, in Science magazine, Christian Schonwiese of the University of Frankfurt am Main, Germany, explained that this summer’s floods were not necessarily linked to anthropogenic-induced increases in carbon dioxide levels. Unfortunately, he then conceded to the notion that fuelling concern about global warming is a laudable aim, even in cases where the science does not back it up. ‘I can put up with a few misinterpretations of details, if the floods leave behind greater public awareness about potential dangers of global warming’, he said (3).

Nobody can doubt that flooding has serious consequences for those on the receiving end. And it is also the case that, with global warming, we can expect increased rainfall. There are also likely to be more floods. But as previous articles on spiked have pointed out, we can expect increased flooding for reasons which have nothing to do with global warming. There is more building on river flood plains, and there are strong preferences for scenic soft river flood defences (rather than effective, but nasty-looking concrete embankments) (4).

However, the environmental crisis message that is being sold in relation to these recent floods is very different from the fairly boring town planning arguments that should be posed. The real claim put forward by Latif, Salt and others is that global warming is causing more extreme climate events. Does this argument stand up?

Writing in Geophysical Research Letters, Konstantin Vinnikov and Alan Robock recently showed that there were no significant trends in the variability of several key example climate indicators over the past 100 years: the US annual average precipitation, the US annual drought severity index, the All-India Monsoon Rainfall Index, and the Southern Oscillation Index (linked to El Nino) (5).

The US annual rainfall is gradually increasing, as one would expect with global warming. Now of course annual rainfall will vary from one year to the next. But it has been a central claim of environmentalists that this variability or change from one year to the next will become far wilder.

But the variability of the US annual rainfall has not changed for 100 years. The Indian monsoon is not changing its variability. The Southern Oscillation is not changing its variability. Despite all the claims to the contrary, there seems to be scant long-term statistical evidence for more climate variability.

What about the concern about increasing numbers of extreme weather events leading to rising insurance claims? The media discussions of mega-storms involves a certain sleight of hand. The 1992 Hurricane Andrew, which hit the eastern seaboard of the USA causing $30billion damage, is always referred to as a benchmark as the most damaging weather event ever, with the implication that hurricanes are getting worse. But this is like saying that Batman 3 is a bigger film than Gone with the Wind. What is being discussed is not the scale of the actual weather event, but the financial consequences of the claims made upon the insurance industry.

Hurricane Andrew was not the biggest or most damaging hurricane to hit the USA in the past 100 years. The biggest hurricane by far was the Florida Keys hurricane of 1935, with wind gusts of up to 200 miles per hour (mph). This was one of only three ‘category five’ hurricanes in the past hundred years, and killed more than 400 people (6). (Hurricane Andrew was only upgraded to a category five on 21 August 2002, 10 years after the event, as new research indicated there were wind gusts up to 165 mph.) If the Florida Keys hurricane hit today, billions of dollars’ worth of damage would be caused.

It was because of the impact upon the insurance industry that Dr Salt described this summer’s European floods as the worst since Hurricane Andrew (7). In these narrow terms, this is true. But is it such a big deal? With increasing wealth, with ever more infrastructure and with increasing incomes so more people can afford insurance premiums, it would be surprising if insurance claims were not rising steeply.

What about the claim that the insurance market is ‘not sustainable’? The financial markets in the City of London have not been able to provide people with sustainable pensions when they retire, sustainable endowments to pay off mortgages on their houses or sustainable health insurance (if you actually have health problems) – so there is no reason to suppose that the City should do any better in providing ‘sustainable’ building insurance.

But isn’t it convenient to shift the failings of the workings of the City on to global warming?

Peter Sammonds is professor of geophysics at University College London, and a contributor to Nature’s Revenge: Hurricanes, Floods and Climate Change, in the Debating Matters series, published by Hodder & Stoughton, 2002. Buy this book from Amazon (UK).

Read on:

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(1) Science magazine, 23 August 2002

(2) Guardian, letters, 22 August 2002

(3) Science magazine, 23 August 2002

(4) Global warming and coastal erosion: American ‘truculence’ or sensible science?, by Peter Sammonds; How to stop the floods, by Nicandro Porcelli

(5) Konstantin Vinnikov and Alan Robock, Geophysical Research Letters, vol 29, no 2, 2002

(6) Konstantin Vinnikov and Alan Robock, Geophysical Research Letters, vol 29, no 2, 2002

(7) Guardian, letters, 22 August, 2002