As Hurricane Irma batters Florida, with Anguilla, Barbuda and Cuba clearing up and Houston drying out after Harvey, it is reasonable to ask whether such tropical cyclones are getting more frequent or fiercer.
The answer to the first question is easy: no. As the Intergovernmental Panel on Climate Change put it recently: “Current datasets indicate no significant observed trends in global tropical cyclone frequency over the past century.”
The trend in numbers of major hurricanes making landfall in the United States has been slightly downward over the past century. Harvey and Irma have ended an unprecedented 12-year hurricane drought, in which not a single category 4 or 5 hurricane made American landfall. So whatever global warming is doing or will do, it is not so far increasing the frequency of such storms.
The answer to the second question is less certain. Hurricane Irma is certainly breaking records: probably the strongest storm in the Atlantic outside the Gulf of Mexico, almost rivalling Hurricane Allen (1980) for the strongest hurricane ever to make landfall, wider in its impact than Hurricane Charley (2004) or Andrew (1992). Last week it sustained its 185mph winds for 37 hours, comfortably beating a record set by Typhoon Haiyan in 2013.
But how much of this is down to better measurement? We will never know exactly how ferocious the winds of the Labor Day Hurricane of 1935 were, or the great Barbados hurricane of 1780. An analysis published last month by the American government’s Geophysical Fluid Dynamics Laboratory stated: “It is premature to conclude that human activities, and particularly greenhouse gas emissions that cause global warming, have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity.”
It remains possible that tropical cyclones are becoming slightly fiercer, but slightly less frequent, which would be consistent with some predictions of climate-change theory.
Incidentally, as the climatologist Judith Curry said of Hurricane Irma last week: “The surprising thing about this development into a major hurricane was that it developed over relatively cool waters in the Atlantic, 26.5C, when the rule of thumb is 28.5C for a major hurricane”. So it was not exceptional warmth, but exceptionally low wind shear (high-altitude wind) that led to Irma’s birth.
Let’s assume that there is a trend towards slightly fewer but slightly more intense hurricanes. What does it mean for policy? Pause to notice one truly spectacular feature of Harvey and Irma: how few people they have killed so far. By stalling near the Texas coast, Harvey caused huge floods in Houston, not quite rivalling those of 1935 in the city but still devastating to many people. Yet they killed only about 60 people. Compare this relatively low number (given the huge population of Houston) with the 10,000 dead in Galveston in 1900, or the 138,000 who died in Cyclone Nargis in impoverished Burma in 2008.
It is a similar story with Irma. That Anguilla and Barbuda have been reduced to rubble with the death of only one person on each is astonishing. I am writing this before Irma fully strikes western Florida, but the state has had more warning than for Hurricane Andrew, which killed 65. People in countries or islands with sufficient prosperity and technology to warn, defend and protect each other are far less likely to die than in the past. Indeed the death rate from droughts, floods and storms globally is about 98 per cent lower than it was a century ago. Wealth is the best defence against storms.
While the cost of damage from storms goes up and up, that’s because there are more buildings and more people in places such as Florida. But as a percentage of GDP the damage done by tropical cyclones has been declining steadily for decades.
Houston’s recovery from Harvey is truly remarkable. Less than two weeks after the storm the airport was open, the water system was working and the electrical grid (which stayed on throughout for most people) was in good order. Hotels are no longer clogged with flood refugees and are taking normal bookings. The Convention Centre, to which victims of the flooding were taken, is reopening for conventions soon. Note that this survivability depends heavily on non-renewable energy: wind farms and solar panels are no use during hurricanes, while gas plants work fine, as do outboard motors on rescue boats.
Adaptation is and always will be the way to survive storms. Given that hurricanes were hitting Florida, Texas and the Caribbean long before the industrial revolution, let alone the 20th century, it would be absurd to suggest that they could somehow be prevented by any climate-change policy. It would be no more absurd to try to promote calm weather through climate policies. (To be clear, I said the same about the record cold December in 2010: it’s not global cooling; it’s weather.) Adapting to cope with possible future storms will be necessary whether they become more intense or not.
The Intergovernmental Panel on Climate Change conceded this in its last report. Vicente Barros, the co-chairman of Working Group 2, said at its launch that “investments in better preparation can pay dividends both for the present and for the future . . . adaptation can play a key role in decreasing these risks”.
Nigel Lawson pointed out 11 years ago in his book An Appeal to Reason that adaptation policies had benefits over carbon-reduction policies: they work unilaterally; can be applied locally; produce results quickly; can capture any benefits of warming while reducing risks; address existing problems that are exacerbated by warming; and bring benefits even if global warming proves to have been exaggerated.
The temptation to blame Irma on fossil fuels or Donald Trump, milking natural disasters for political gain, proved irresistible to some. This makes no more sense than blaming the Syrian civil war on climate change, rather than man’s inhumanity to man, which Barack Obama, the Prince of Wales, Bernie Sanders, Friends of the Earth and the World Bank were all tempted into doing. “In our assessment,” said a study last week by social and climate scientists, “there is thus no good evidence to conclude that global climate change-related drought in Syria was a contributory causal factor in the country’s civil war.”
Matt Ridley, a member of the British House of Lords, is an acclaimed author who blogs at www.rationaloptimist.com.