A recent study reveals that contrails or condensation trails left by aircraft are contributing more to global warming than the carbon dioxide (CO2) emissions from the aircraft. Based on projections, the impact of contrails on climate change will triple by 2050 compared to their effect in 2006. The reasons for this increase include changes in flight patterns, increased air traffic, and advancements in fuel efficiency.
Factors Driving Increase In Contrails Impact
Modern airplanes are flying at slightly higher altitudes than their predecessors, a factor that leads to more contrail cloud formation particularly over the tropics. Additionally, air traffic volume is on the rise. Fuel efficiency improvements also contribute to the expansion of contrails. It is predicted that the impact of contrail cirrus clouds will be greater over Northern America and Europe – the busiest air traffic areas globally – and in Asia, where air travel is accelerating.
Contrail Formation and Characteristics
Contrails form when hot, humid exhaust from jet engines mixes with the atmosphere, which at high altitude has much lower vapor pressure and temperature than the exhaust gas. The water vapor in the jet exhaust condenses and may freeze, creating a cloud. While most contrail cirrus clouds dissipate quickly, under certain conditions, they can last for hours, absorbing thermal radiation emitted by the Earth and thereby warming the atmosphere.
Implications of Contrails on Climate
Jet engine exhaust contains a mix of substances including carbon dioxide, oxides of sulfur and nitrogen, unburned fuel, soot, metal particles, and water vapor. The soot offers condensation sites for water vapor, leading to contrail formation. The thickness, extent, duration, and behavior of contrails can predict weather patterns; a thin, short-lived contrail indicates fair weather while a thick, long-lasting contrail signals an impending storm.
Flight Industry’s Impact and Significance
Air traffic was responsible for about 5% of human-made climate change influence in 2005. With air traffic doubling approximately every 15 years, contrails are the aviation industry’s most significant climate influencer, surpassing even CO2 emissions from planes.
| Year | Impact of Air Traffic on Climate Change |
|---|---|
| 2005 | 5% of humans’ influence |
| 2050 (Projected) | Triple the impact of 2006 |
The Role of Climate Policies and Contrails
Current policies aimed at reducing aviation’s impact on climate change mainly focus on CO2 emissions, largely overlooking the impact of contrails. The study prompts that contrails should be a significant factor considered in climate policies. It advocates for the recognition and consideration of non-CO2 emissions like contrail cirrus during the formulation of emission trading systems or agreements like the CORSIA Agreement.
Solution to Reducing Contrails’ Climate Impact
Achieving cleaner aircraft emissions could alleviate the issue. Reducing the number of soot particles emitted by aircraft engines decreases the number of ice crystals in contrails, thus mitigating the climate impact of contrail cirrus. However, the reduction in soot emissions needs to be substantial for a significant effect. Even a 90% decrease would still result in contrail cirrus clouds causing more warming in 2050 than they did in 2006. Thus, the best option to mitigate this effect and reduce aviation’s carbon footprint is to decrease flight frequency.