Climate change means more severe storms in both the Atlantic and the Pacific. But governments are getting a bit better at preparing for them
People living on opposite sides of the planet have in recent days felt the disastrous consequences of distant rumblings in the deep ocean. In America, they are still suffering the devastation left by Hurricane Florence, which made landfall in North Carolina on September 14th. Less than 12 hours later super-Typhoon Mangkhut tore into the Philippines, subsequently to hit Hong Kong and southern China. Mangkhut packed a bigger punch: a category 5 storm when it first hit land, to Florence’s category 1. But the impact of both was linked to rising levels of greenhouse gases in atmosphere, which are changing the climate and warming the sea.
For that reason, future storms are also likely to be more severe than in the past. Florence and Mangkhut have shown the progress that has been made in preparing for them and mitigating the damage － but also highlighted how vulnerable many communities remain, especially in Asia.
The link with climate change comes from the accumulation in the?atmosphere of greenhouse gases produced by the industrial burning of fossil fuels and by deforestation. They create an imbalance in the energy flowing in and out of the planet, driving temperature up. About 90% of that additional energy ends up stored in the oceans. Researchers who monitor sea temperatures down to 2,000 metres have plotted a steady rise since the 1950s, reaching a record high last year. So far, 2018 is on course to set a new record.
Kevin Trenberth of the US National Centre for Atmospheric Research says this explains storms like Florence and Mangkhut. Tropical storms in the Atlantic (known as “hurricanes”) and Pacific (“typhoons”) draw their energy from this abyssal heat store. Warmer oceans mean more intense and long-lasting storms. Climate models have long forecast this. Moreover, sea levels are rising at a rate of 3mm per year. Two factors explain this: water expands as it warms; and glaciers are melting at both poles. Higher seas mean storm surges reach farther inland. And, as the atmosphere warms, it can hold more moisture that eventually falls as precipitation.
Recent studies have explored these effects in detail, using real events. Earlier this year, for instance, Mr Trenberth showed that deep-ocean temperatures just before Hurricane Harvey, which led to disastrous flooding in Houston in August 2017, were at a peak globally and in the Gulf of Mexico.
Data recorded just after the storm revealed a drop in the heat content of the Gulf that closely matched the amount of rain unleashed by the hurricane. Mr Trenberth and his colleagues concluded that Harvey “could not have produced so much rain without human-induced climate change.” Kerry Emanuel, of the Massachusetts Institute of Technology, estimates that a hurricane like Harvey in 2017 was made six times more likely by human greenhouse-gas emissions, and that by 2100 the risk will be 18 times higher than it was in the late 20th century.
A man who knows his stormy
Florence received an awestruck presidential reception. “One of the wettest we’ve ever seen from the standpoint of water”, noted President Donald Trump. In fact, America has endured far wetter and more damaging. Moody’s estimates that Florence caused between $17bn and $22bn in damage. Katrina, which devastated New Orleans in 2005, cost $160bn in current dollars; Harvey cost $125bn; Maria, which affected Puerto Rico in 2017, cost $90bn.
The death toll of Florence, estimated at 37, is well behind those seen by Katrina, which killed? 1, 833, and Harvey (88). A recent study calculated that Maria killed 2,975, over a longer period, though Mr. Trump, sensitive to criticism of his administration’s flat-footed response to that disputed those figures. In contrast, a sensible government reaction to Florence probably helped limit damage and loss of life. Mandatory evacuation orders were issued three days before landfall. New Orleans only got such an order on the eve of Katrina’s arrival.
That Florence was not a chart-topping storm is small comfort to the North Carolinians whose homer and businesses were destroyed. Local economies could take years to recover. Some homeowners will be compensated by national flood-insurance programme, which is subsidised by the government, in effect paying people to live in areas at high risk of? flooding. Even so, the Federal Emergency Management Agency estimates that 40% of small businesses never reopen after a natural disaster. The state’s livestock industrial has already taken a beating. The state agriculture department said that Florence had killed 3.4m chickens and drowned 5.500 pigs. Such casualties are expected to rise.
