Passengers, prepare for splashdown. Take-off may have to wait for low tide. By 2100, thanks to rising sea levels, around 100 of the world’s airports could be below mean sea level and at least 364 will be vulnerable to flooding, Climate News Network reports.

And that’s assuming the world’s nations keep a promise made in 2015 and confine global heating to no more than 2°C above the average maintained for most of human history. If humans go on burning fossil fuels and clearing forests at the present rate, then at least 572 of the world’s airports could be at risk of flooding from extreme tides, according to a new study in the journal Climate Risk Management.

These things have already happened: in 2018 a typhoon storm surge inundated Kansai International Airport in Osaka Bay, Japan. Superstorm Sandy in 2012 closed New York City’s La Guardia Airport for three days. One-tenth of the planet’s population lives on coastlines less than 10 metres above sea level.

Airports grow up around the great cities: they require flat land and a clear flight path. Coastal flood plains, wetlands, and reclaimed land provide exactly that.

Serious Risk

“These coastal airports are disproportionately important to the global airline network, and by 2100 between 10 and 20% of all routes will be at risk of disruption,” said Richard Dawson, an engineer at Newcastle University in the United Kingdom. “Sea level rise therefore poses a serious risk to global passenger and freight movements, with considerable cost of damage and disruption.”

He and a colleague looked at the world’s 14,000 airports and helicopter pads to identify 1,238 airports in what geographers call low elevation coastal zones: that is, down by the seaside. Of these, 199, serving 3,436 routes, were in the U.S.; China had 30 airports serving 2,333 routes.

They found that just 20 airports at risk handled more than 800 million passengers in 2018—approaching a fifth of the world’s passenger traffic that year—and nearly 16 million tonnes of cargo: one-fourth of all the world’s air freight that year. They then started looking at what climate change could do to all that business.

Even before the shutdown of traffic because of the global pandemic, the world’s airlines had been feeling the heat. Research teams have confirmed that ever higher global temperatures mean more atmospheric turbulence at altitude; that wind speed changes will slow flights and raise costs; that extremes of heat could even close airport runways and delay flights for extended periods.

Now Dawson and his colleague have compiled a table of hazard rankings for flooded airstrips under a range of climate change scenarios.

Right now, 269 of the world’s airports are at some risk of coastal flooding. This number must rise: by how much, and at what cost, depends on what actions the world takes. But the researchers calculate that by 2100 the risk of disruption could increase 17-fold, or even 69-fold. And because so many important airports are already at or near sea level, up to a fifth of all the world’s routes will be at risk.

And that means higher costs for flood protection, or action to raise airport sites, or relocation. The choice is to adapt or, quite literally, to go under.

“The cost of adaptation will be modest in the context of global infrastructure expenditure,” Dawson said. “However, in some locations the rate of sea level rise, limited economic resources, or space for alternative locations will make some airports unviable.”—Climate News Network