Aviation and Its Environmental Impacts
2 February 2024 | Blog #3
Aviation is faced with three major challenges in the long term regarding its environment: 1) 'Climate Change', 2) 'Sustainability', and 3) 'Carbon Neutrality'. However, before delving into specific impacts, attention should be drawn to the rapid development of commercial aviation. Over a span of 50 years (1969 to 2019), aircraft engine efficiency has increased by 80%. It's also worth noting that from 1989 to 2019, a period of 30 years, commercial aviation production (expressed in RPK - Revenue Passenger Kilometers) increased fourfold, while emissions from it only doubled. These figures illustrate the rapid development of this mode of transportation in conjunction with technological innovations.
Aviation is definitely responsible for three major impacts due to the consumption of kerosene: emission of carbon dioxide (CO2), nitrogen (NOX), and contrails. CO2 emissions from aviation for the year 2023 were estimated at around 70 million flight hours (worldwide). This translates to approximately 700 million tons of carbon dioxide emitted. The fundamental issue with carbon dioxide is its 'longevity', as CO2 persists in the atmosphere for several decades (!). Therefore, the cumulative approach has a drastic effect: when added over the years, this leads to massive impacts on global warming.
NOX, as a greenhouse gas, has greater impacts on life on Earth than CO2. Compared to CO2 (carbon dioxide), NOX gases have a shorter atmospheric lifespan, but they are more potent greenhouse gases in many respects. Aspects such as greater heat retention, influence on the ozone layer, and involvement in atmospheric reactions are significant reasons why NOX gases are considered significant climate drivers. NOX gases have a faster atmospheric reaction and distribution than CO2. While CO2 remains in the atmosphere for long periods, NOX gases can have faster and more localized impacts.
Lastly, contrails take center stage. The typical cruising altitude is 10 km above ground where temperatures reach -40 degrees Celsius or colder. According to the DLR (German Aerospace Center), this cold air cannot absorb the water vapor coming from aircraft engines as well as warmer air. What happens next is akin to a sponge saturated with water that can't absorb any more liquid: water droplets form, creating artificial clouds (contrails). These contrails often persist for several hours, are dispersed by the wind, and thus form additional artificial clouds (cirrus clouds). It seems clear that contrails contribute to climate warming, potentially even as strongly as the CO2 emitted by airplanes. This is because contrails, acting somewhat like large veils of mist, prevent the sunlight and warmth from escaping the Earth back into space. Consequently, they would enhance the so-called greenhouse effect, which heats our climate. Or do contrails possibly have the opposite effect? Does the bright surface of the clouds reflect sunlight so strongly that a portion is directly radiated back into space? In that case, contrails would counteract the warming of our planet. In other words, do clouds act like the glass roof of a greenhouse or like a mirror? Currently, it is assumed that contrails have a temporary effect lasting 10 to 15 hours.