Understanding Contrails: today's initiatives and future perspectives

Have you ever wondered about those cloud-like trails left behind by aircraft? These formations are commonly known as contrails. Now, you might wonder, why the notoriety? After all, the sky is no stranger to clouds. So, what difference do a few additional clouds make?

As it turns out, quite a bit. 

In this comprehensive two-part series, we will explore the fascinating world of contrails, from their formation to their environmental impact. By delving deeper into this topic, you will understand why contrails are increasingly gaining attention in the field of aviation and environmental science. 

  1.  Understanding contrails: formation, impact, and prevention.
  2.  Understanding contrails: today's initiatives and future perspectives

In part 1, we reviewed the main factors of contrail formation, their impact, and the existing solutions. Now, let's review what the main stakeholders are doing on the topic to prepare for this new non-CO2 emission era. 


Addressing the regulation of contrails

Given the complexity of researching contrails, which span multiple disciplines, including meteorology, aircraft performance, thermodynamics, and data science, the level of uncertainty in this field is consequent.

This multidisciplinary nature underscores the critical role of regulators in facilitating the industry’s progress. Regulatory bodies need to promote an environment conducive to research and collaboration as well as promoting incentives to engage the private sector. Without such support and a framework that encourages innovation, effectively addressing this crucial aspect of aircraft emissions remains challenging. 

What are the regulatory perspectives on contrails?

The European Union's ongoing actions on the regulation of contrails

The European Union (EU) seems to be the most invested regulatory body focusing on contrails. This stakeholder has already expressed its desire to include non-CO2 emissions, such as contrails, in the net-zero emissions goal of 2050. The organization understands the topic's indeterminacies but is also aware of the harmful impact of these cloud formations. And so, these uncertain elements won't stop them from monitoring contrails. 

Related content >>> Fly Net-Zero 2050: how airlines use data to improve fuel efficiency?

Moreover, in its efforts on the subject, the organization proposed a Monitoring, Reporting, and Verification (MRV) solution. It intends to develop the MRV IT solution during 2024 and start monitoring contrails in 2025. 

The European Union wants to start the MRV as soon as possible. Still, they highlight that the solution will adapt to the latest industry models and advancements. The MRV will run between 2025 and 2026, after which results reviews and discussions regarding regulations will start. They trust the aviation industry's technology will be advanced enough to discuss regulations by then. The European Union insists on basing final decisions on trustworthy scientific information to guarantee well-informed decision-making. 

Non-CO2 NRV consultation meeting - EU

Learn more about this MRV project here: Non-CO2 MRV Kick-off Meeting - European Commission

Other initiatives to study contrails 

Other regulatory bodies are also tuned into the topic of contrails. In the United States, for example, major players like Boeing, NASA, and the Federal Aviation Administration (FAA) have teamed up for a long-term contrails research project. They are testing emissions using Boeing's ecoDemonstrator as part of their collaborative efforts. This research project aims to understand better how the use of SAF impacts contrails.
However, as of now, there hasn't been any official discussion about future programs or regulations on the topic.

Companies and initiatives studying contrails

In addition to studies and regulation initiatives, multiple exciting collaborative projects are being developed due to the notoriety of the topic. 

These projects are filled with the expertise and advanced technologies required to delve into the intricacies of contrails. Let's take a closer look at one of these intriguing
 projects: Project Contrails 

Google Research and an MIT research lab are teaming up with American Airlines and Delta Airlines, respectively. The big technology laboratories are developing a data-driven method to determine contrail's formation areas. Airlines provide them with their infield validation through flight experimentation to analyze the feasibility of operations avoiding the Ice Super Saturated Regions (ISSRs).

Related content >> Understanding contrails: formation, impact, and prevention

 Google and MIT use satellite images to detect contrails and track their evolution. Nevertheless, there are still some limitations. There is a big complexity in assigning contrails to the aircraft that has produced them — a critical piece of information needed to determine under which conditions the formations are created.   

The expected evolution of this technology combines the satellite’s information with data from on-ground cameras, which can provide information on the early stages of contrails where satellites cannot capture them. 

 contrails explorer

Figure 1. Contrails Explorer Satellite Image.
Source: Google Contrails Explorer

The figure above, extracted from Google’s Contrail viewer, shows an example of what Google Research does with satellite imaging regarding contrails. Due to high-quality satellite image requirements, the area covered covers only the United States. Currently, only the images available from the satellite GOES-16 correspond to the high-quality standards needed for this project. 

Another initiative we can point out is Reviate. 

Reviate is carrying out research using physical models to compute contrails and is collaborating with many industry technology giants to improve and validate the model. They offer an interactive map in which you can visualize the contrails computed by their model. This map allows you to select different aircraft to see what ISSRs they go through and what their contrail impact is.

reviate contrails map

Figure 2. Contrails Map with the contrails heating in red.
Source: Reviate contrail's map

Future perspectives: Can contrail avoidance be possible? 

While this remains an open question, ongoing research, and technological advancements offer glimpses of hope for a future where contrails' problematics will be addressed. 

Banning flights over "climate-sensitive" regions to reduce contrail formations

One potential solution to minimize the impact of contrails on the climate is to ban flights over certain 'climate-sensitive' regions. This will allow flights to sidestep Ice Super Saturated Regions during specific times of the day when 'big hits' are more likely. However, this approach would pose a new challenge for Air Traffic Managers (ATMs) and could potentially reduce airspace availability. 

The MUAC has tested this method and found that while contrails were avoided, predicting ISSRs was trickier than anticipated.  

Furthermore, during the Sustainable Skies Conference: Contrails in Focus event held by Eurocontrol, ATMs pointed out the intricate nature of Europe’s airspace and expressed concerns about introducing such new measures that would compromise safety.

For this solution to be successful and for ATMs to be reassured, the ISSR prediction must increase in precision. Predictions must be longer-term to allow collaboration between airlines and ATMs and to avoid further tactical operations requirements. 


Planning flight trajectory to avoid Ice Super Saturated Regions

Another alternative is for airlines to consider ISSRs during their flight planning and operations, with pilots actively avoiding these areas. However, this approach may not always be effective. If one aircraft avoids creating a contrail by steering clear of a certain area, but later another aircraft passes through the same region and forms a contrail, the initial avoidance effort may be in vain. 

The complexity of this issue underscores the importance of collaboration in addressing the non-CO2 impact of contrails. 

Pilots' workload is already high in managing delays, ensuring safety, and optimizing fuel efficiency during a flight. Adding the task of contrail avoidance could further burden their missions and pose a safety risk.

Therefore, it is crucial to introduce contrail-related operations slowly and with tools to help decision-makers automate these processes as much as possible. 

To sum up:

We see a complex dilemma with no easy solution. However, with stakeholders' collaboration and the development of new technologies, the industry is actively trying to find solutions to reduce the impact of contrails on the climate.  



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