Look with your eyes, not your hands. You were probably told that at some point growing up, as your eagerness to see and experience something new was checked by a wary adult. Humans now handle the Earth in a similarly precarious manner. Our desire to explore the world is increasingly plagued by an awareness that international travel harms the very places we spend so much to visit.

There are more commercial flights taking off today than at any other time in history. Many of them will take tourists to see the world’s most striking natural beauty. Snorkelling on the Great Barrier Reef, trekking in the Amazon, boat tours in the Arctic – cheap air travel has opened more of the world to tourism and ensured more people can afford to see it.

But it has come at a heavy cost to the planet. Aviation currently accounts for 2-3% of all annual carbon dioxide (CO₂) emissions. That may not sound a lot, but aeroplanes heat the atmosphere by up to three times more than their CO₂ emissions alone because they release nitrogen oxides – powerful greenhouse gases – and create contrails in their wake which trap even more heat in the atmosphere.

A single flight from London to New York is estimated to melt about 3.3 square metres of Arctic ice. Greta Thunberg – the campaigner who started the youth climate strikes – is making that journey to attend the UN annual climate summit in September. Rather than take a transatlantic flight and contribute to yet more ice melting, she’s sailing from Plymouth on a zero-carbon yacht.

Meanwhile, the aviation industry is predicted to double by 2040 – doubling the number of flights and the number of people taking them. Earth has warmed by 1°C since pre-industrial times and already many coral reefs are struggling beyond their thermal limits, while rainforests are drying out. Without drastic action, there may be little cause for exploring the world’s natural beauty in future, as there’ll be much less of it to see.

In this fifth issue of Imagine, we asked researchers to scan the horizon of air travel. Does the climate crisis demand we turn our backs on the skies and remain permanently grounded? Or could a technological breakthrough keep our travel obsessions afloat?

We’re flying towards the climate emergency

“Our house is on fire”, Thunberg said, as she addressed the World Economic Forum in January 2019. Few analogies capture the urgency of the climate crisis so succinctly.

Political recognition of the crisis has been sluggish, but at the time of writing four countries have declared a climate emergency: the UK, France, Canada and Ireland. Worldwide, 935 local government bodies, which cover 206m people in 18 countries, have done the same.

In the UK, parliament voted to declare a climate emergency on May 1 2019. But less than a year before that, MPs voted by 415 votes to 119 to build a third runway at London’s Heathrow airport – already the largest single source of CO₂ in the UK.

Had Britain’s parliamentarians suddenly realised their error a year on? More likely, they are like most of us who recognise the threat of the climate crisis but aren’t aware of – or would rather not think about – the scale of the change that’s needed to avert it.

That’s a problem that undermines many pledges to reduce emissions – and not just those made on the international stage. Within the towns and cities we live, councils commit to radical action in one breath while approving plans that will ramp up emissions in the next. The city council of Leeds recently declared a climate emergency and signed off on a strict carbon budget which commits the city to emitting no more than 42 megatonnes of CO₂ between 2018 and 2050. At the same time, the council has endorsed the expansion of Leeds Bradford Airport – promising new transport links and a commercial centre nearby.

Airport expansion – In 2018, four million passengers used Leeds Bradford Airport. With the expansion of the main terminal, the number is predicted to double to eight millioin by 2030.

Climate impact – All those additional flights would amount to more than double the 2030 target emissions for the entire city of Leeds.

Up and up from 2030? – If passenger numbers continue growing after 2030, even at a slower rate, emissions from Leeds Bradford Airport would overshoot the city’s carbon budget by a factor of nine by 2040.

But even if the airport doesn’t expand and the number of passengers using Leeds Bradford remains at today’s levels, all flights between 2018 and 2050 would still consume the city’s entire carbon budget.

Written by Jack Marley. Republished with permission of The Conversation.