Climate change is one of the most pressing challenges of our time. Many industries are moving toward decarbonization, and aviation has started to follow suit. The airline industry contributes about 3.5 percent of all anthropogenic activities, and accounts for nearly 2.5 percent of global carbon dioxide emissions. But what does this mean for the average Joe taking a flight? In this industry, emissions are often measured in ‘per revenue passenger kilometer (RPK)’—the number of revenue passengers multiplied by the distance traveled. Currently, aviation produces about 100 grams of carbon dioxide per RPK. These numbers vary with routes, which determine the type of aircraft and its efficiency.  

Nearly half of aviation’s climate impact, however, comes from condensation trails or ‘contrails’, as they are commonly called. These thin, line-shaped clouds form when water vapor emitted from engine exhaust freezes at high altitudes. Contrails trap heat in the Earth’s atmosphere which prevents radiation from escaping and thereby intensifying global warming. After a sharp drop during COVID-19, air travel demand has returned to pre-pandemic levels. It is expected to grow by 4.3 percent per year over the next few decades. This will further exacerbate aviation’s environmental footprint. 

Aviation emissions degrade air quality. This factor is often overlooked in mainstream discussions of aviation sustainability. It accounts for almost half of the social cost. Fuel combustion inevitably releases unburnt carbon or soot which contributes to the increase in particulate matter in air. Soot from aviation is particularly concerning near airports, where emissions during takeoff and landing are most prominent. While cruising, soot emissions are generally removed from the atmosphere through natural phenomena such as rain. Particulate matter pollution is linked to serious health issues which include heart attacks and asthma, especially in individuals with preexisting heart and lung diseases.  

The nitrogen oxides (NOx) produced during combustion contribute to the formation of ozone in the upper troposphere. Unlike the protective ozone layer in the stratosphere, this ground-level ozone can reach the Earth’s surface and degrade air quality. Similar to particulate matter (PM), ozone pollution can worsen respiratory conditions like bronchitis and inflame the airways. Being highly reactive, this surface ozone layer contributes substantially to PM pollution by oxidizing pollutants from other industries. Hence, it is a bigger contributor to pollution than just soot. This effect is especially severe in areas with existing industrial pollution where aviation further degrades air quality. Moreover, noise pollution from aircraft takeoffs and landings near airports also poses health risks such as hearing loss and high blood pressure. 

But there is a silver lining to all this!