Early this summer, Phoenix’s international airport cancelled several dozen flights as the thermometer in Arizona was heading for a scorching 48°C. Dramatically, at that temperature air molecules may not be dense enough to provide the indispensable lift for aircraft to take off.

Last year was the hottest on record – surpassing 2015, which surpassed 2014 – and hints are already suggesting that 2017 will rise even further. With such a progression towards a warmer climate, how often will air traffic be disrupted? Can a fast-growing airline industry cope with the perils of a thinner atmosphere?

It is not a trivial question. Civil and commercial aviation are a crucial element of economic growth. According to the World Bank, around 15.5 billion tons of goods were shipped in 1970, up to 195 billion in 2015. There were 310 million passengers in 1970, up to 3.4 billion two years ago. The International Air Transport Association expects 7.2 billion passengers in 2035, yet another doubling in 20 years.

Civil aviation alone is responsible for two per cent of global CO2 emissions. However, if we add the nitrogen oxides, the water vapour and the particulates it emits, its influence on climate’s arithmetic is considered to be closer to four per cent. Major airlines have long been reluctant to swear an oath on emission reduction. They successfully rebelled when, in 2012, the European Commission tried to include aviation in its Emission Trading Scheme. During the painstaking negotiations that brought about the Paris Accord, just mentioning aviation was taboo.

Luckily though, last November the International Civil Aviation Organization (ICAO) finally acquiesced to a carbon offsetting scheme. The agreement doesn’t urge the industry to innovate, but it may be a good starting point. A few airlines are paving the way (Virgin Atlantic cut its emissions per mile travelled by 22 per cent in ten years), even though the vast majority still see their business as inescapably linked to fossil fuels.

The US is now retreating from the Paris Accord. But the aviation agreement, in ICAO’s own words, ‘complements’ Paris. So no one really knows its fate. The voluntary period is set to begin in 2021. Were the American carriers to step away from it, it will never really take off. Just like their airplanes on a future, sweltering summer day.

This was published in the September 2017 edition of Geographical magazine.