Billionaire Bill Gates highlighted how flights contribute to planetary warming, beyond carbon emissions from fossil fuel combustion. In an interview cited by The Times of India on 10/10, Gates explained that aircraft also produce indirect emissions through "contrails"—the white streaks left behind as planes move, resembling brushstrokes across the sky.

Bill Gates, co-founder of Microsoft, has been an investor in climate change solutions since 2015. In 2021, he authored "How to Avoid a Climate Disaster," a book that analyzes the causes of global warming, the challenges of energy transition, and strategies for achieving Net Zero emissions.

The aviation industry refers to these "cloud streaks" as condensation trails, or contrails. Aircraft emit tiny soot particles from incomplete fuel combustion. When these particles pass through atmospheric regions with suitable temperature and humidity, water vapor condenses around them, forming ice crystal trails.

Bill Gates discusses the phenomenon of aviation contrails. Screenshot from Gates Notes video.

According to Gates, most contrails dissipate quickly. However, some persist for hours, spreading into high-altitude clouds known as cirrus clouds. These clouds trap heat that would otherwise escape into space. "Long-lasting contrails cause about one-half of the temperature increase from aviation," he stated.

Avoiding these persistent contrails is simple and low-cost compared to other climate solutions. The atmospheric conditions conducive to their formation are typically found in narrow bands. The aviation industry would only need to adjust the routes of about 5% of global flights to bypass these areas.

The technology billionaire estimates these route adjustments would increase the average fuel consumption for all flights by only 0,1%. The cost to avoid creating contrails could be as low as one to two USD per ton of CO2 reduced. In contrast, sustainable aviation fuel (SAF), a common emissions reduction solution for the industry, costs up to 130 USD per ton of CO2 removed.

Solution to avoid contrail-forming regions. Source: Contrails.org.

Gates introduced Contrails.org, a non-profit organization he co-founded, which is developing free open-source software for airlines to use in flight planning to avoid contrail-forming atmospheric regions. Last year, Contrails.org partnered with American Airlines and Google Research on over 100 flights to implement contrail avoidance measures.

Gates acknowledged his own use of a private jet, a significant contributor to planet-warming emissions. He is actively working to use sustainable aviation fuel and implement solutions to offset his family's aviation emissions. With this new finding, he hopes that contrail avoidance will become an integral part of modernizing the aviation industry's air traffic management system.

Bao Bao (according to The Times of India, Gates Notes)