The International Air Transport Association (IATA) has issued a call for urgent measures to deepen understanding of aviation contrails’ formation and climate effects, aiming to develop effective mitigation strategies.
In its newly released report titled “Aviation Contrails and their Climate Effect: Tackling Uncertainties and Enabling Solutions,” IATA emphasizes the necessity of enhanced collaboration between research, technological innovation, and policy frameworks. This collaboration is crucial to address aviation’s non-CO2 emissions by leveraging more comprehensive atmospheric data.
The report underscores the intricate nature of contrail science, highlighting gaps in understanding the formation of contrails, their persistence, and their impact on climate.
A critical challenge identified in the report is the lack of high-resolution, real-time data on atmospheric conditions, particularly humidity and temperature at cruising altitudes, which impedes accurate contrail forecasting.
“The industry and its stakeholders are working to address the impact of non-CO2 emissions on climate change, particularly contrails. To ensure that this effort is effective and without adverse effects, we must better understand how and where contrails form and shrink the uncertainties related to their climate impact. “Action now” means more trials, collection of more data, improvement of climate models, and maturing technologies and operations,” said Willie Walsh, IATA’s Director General.
“Formulating and implementing regulations based on insufficient data and limited scientific understanding is foolish and could lead to adverse impacts on the climate. That is why the most important conclusion from this report is to urge all stakeholders to work together to resolve current gaps in the science so that we can take effective actions,” he added.
With current levels of understanding, the report recommends that in the immediate term (2024-2030), the priority for mitigating aviation’s climate change impact should be on reducing CO2 emissions over the uncertain gains that could stem from contrail detection and their mitigation.
Over this time, increasing airline participation in sensor programs, continuing scientific research, and improving humidity and climate models should be the focus of work on contrail mitigation.
The report notes that mid-term actions (2030-2040) should involve establishing standards for data transmission, continuous validation of models, and encouraging aircraft manufacturers to include provisions for meteorological observations, as well as selected avoidance.
Longer-term actions (2040-2050) include aircraft being able to continuously provide data and the models and infrastructure should be there and be reliable.
The community will have at this point a more complete understanding of the non-CO2 effects of alternative fuels, with extended mitigation measures.
These action items collectively aim to mitigate the climate impact of aviation while advancing scientific understanding and technological capabilities.
Background on aviation’s non-CO2 emissions
Aviation’s impact on climate extends beyond CO2 emissions, with non-CO2 effects such as contrails and nitrogen oxides (NOx) also contributing to global warming.
Persistent contrails, formed in ice-supersaturated regions, can transform into cirrus clouds which reflect incoming solar radiation (during the day) as well as trap outgoing heat.
On balance, it is understood that contrails have a warming effect on the climate, with diurnal, seasonal, and geographical variations. However, despite extensive studies, significant uncertainties exist for the capacity to predict individual contrail formation and their specific climate impact.
Initiatives and Trials: Recent collaborations among meteorologists, climate researchers, airlines, and aircraft manufacturers have yielded new insights that underscore the need for enhanced data collection and analyses of the likely air traffic network complications regarding any solutions.
Trials with modified flight paths and alternative fuels have shown potential yet limited efficacy due to the variability of atmospheric conditions and the localized nature of where contrails occur.
Technological Advances and Future Directions: Advancements in developing humidity sensors to be placed on aircraft are critical for contrail prediction and avoidance strategies. Current sensor technology on commercial aircraft lacks the required sensitivity and response time, and there are only a handful of such sensors in operation at altitude.
Ongoing research aims to develop more accurate, robust, and scalable solutions, and the use of sensors on a limited population of aircraft would allow the necessary improvement and validation of numerical weather prediction models.