All three realms that humans inhabit—land, sea, and sky—have been thoroughly polluted. This pollution is causing us to reconsider our very existence. One realm that is often overlooked, however, is aerosol pollution from jet aircraft. Unlike pollution at ground level, which we share right across the world, the part of our atmosphere that rises right up over our borders remains, for the most part, pristine. Jet engines are cleaner and more efficient than they were, say, a couple of decades ago. Yet the sheer volume of air traffic makes aircraft a significant source of aerosol pollution.
Tens of thousands of tons of greenhouse gases are contributed to the atmosphere by airplanes, the major ones being carbon dioxide (CO2) and nitrogen oxides (NOx). Aircraft emissions are a major source of nitrogen oxides in the environment. Unlike most power plants, which exhaust emissions at ground level, airplanes release their pollutants at high altitudes, where their effects are magnified.
The Role of Greenhouse Gases
A source of CO2 emissions, the primary greenhouse gas that traps heat in the atmosphere, is aviation. Engines also emit NOx, which reacts with other pollutants to create ozone, a key component of smog. These emissions, when they happen at high altitudes, yield contrails—ice crystals that can persist in the atmosphere and behave like clouds, intensifying the greenhouse effect.
In addition, the aviation industry emits ultrafine particles (UFPs) and soot, which can harm human health. UFPs are able to penetrate deeply into the lungs, and they have been associated with an array of respiratory problems. However, soot is even worse because, in addition to creating local pollution problems, it is also linked to a number of serious health effects, especially for people with preexisting conditions.
The Impact of Contrails
Studies suggest that contrail clouds might warm the planet more than any carbon dioxide emissions from aircraft produced in the last century. Contrails may hang in the atmosphere for a long time, and some may even say that they constitute a form of atmospheric geoengineering, which is “a deliberate and large-scale intervention to counteract the undesirable effects of global warming.” Unlike CO2, which can remain in the atmosphere for centuries, studies have also suggested that the carbon produced by aircraft is a more potent warming agent in the atmosphere, particularly when it comes to the formation, duration, and hanging around of the clouds that we call contrails.
When an aircraft flies through a cold atmosphere, water vapor from the jet engines condenses around particles of soot and forms ice crystals that become contrails. Studies show that unlike low-level clouds that help cool the atmosphere, contrails may warm it up. One study from 2011 predicted that the cloud of contrails our planes leave behind could cause climate warming equivalent to three times as much carbon dioxide by 2050.
The Need for Change
Although many initiatives exist to reduce carbon emissions from aircraft, and myriad treaties and regulations purport to manage countries’ emissions, the comprehensive climate impact from aviation is largely ignored.
Take, for instance, a program from the United Nations designed to manage nations’ carbon emissions. This program attempts to align countries’ CO2 emissions—with somewhat mixed results—but wholly overlooks the significant, and in many ways, much more dangerous, warming impact of contrails.
A few researchers advocate changing the way planes fly to reduce contrail formation. But doing this could cause them to burn even more fuel and produce even more CO2. In the end, the best way to address the contrail issue is not to beat up on the planes or the pilots that fly them, but to find cleaner-burning fuels.
Without a doubt, the aviation sector contributes to worldwide climate change. The justification is obvious:
• Climate science is complex, but the warming effect of aviation is clear.
• We are living in an era of climate change, and to safeguard our atmosphere, we have to grasp the complete ramifications of flying.
Tackling the aviation climate crisis calls for exciting new ideas and a firm commitment to an emerging sustainable aviation industry. This is not an airspace problem; it is a planetary problem.
Capt Indira Vashishta is an ex-airline pilot, motivational speaker and an eminent columnist.
