If you've ever looked at the sky as a plane flies overhead, you've probably seen the long, white, cloud-like lines they leave behind. These lines are called contrails, and they're such a common phenomenon in aviation that most people don't blink when they see one in the sky. What are contrails?that's right?
Contrails are more than just a by-product of aviation: they are a visible reminder of the complex relationship between air travel and the Earth's climate. As a travel journalist, I've traveled the world for years and often marveled at the beauty of contrails but never realized their deeper meaning. But recent research is shedding light on the environmental impacts of contrails, prompting us to rethink our approach to air travel.
Read on for some fascinating facts about airplanes, including what contrails are, new research on their environmental impact, and what researchers, airlines, and travelers can do about it.
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What are contrails?
Contrails, short for condensation clouds, are created when hot, moist exhaust gases from an airplane's engines come into contact with the cooler, lower pressure atmosphere at high altitudes. This process causes the water vapor in the exhaust to condense around tiny soot particles, forming ice crystals and creating the white streaks we see in the sky. These clouds can disappear quickly or linger for a long time, depending on atmospheric conditions.
Several factors influence the formation of contrails, including the type of aircraft engine and the amount of soot they produce. Modern engines are designed to be more fuel efficient, which means they emit fewer soot particles, potentially shortening the lifespan of contrails. But even with these advances, contrails aren't going away. And this is a problem, because studies have shown that contrails trap heat in the Earth's atmosphere and contribute to climate change.
Are contrails bad for the environment?
Contrails may seem harmless, but they have a huge impact on the climate. In fact, they may cause more warming than the carbon dioxide (CO2) emitted by the aircraft itself. The ice crystals in contrails trap heat in the atmosphere, creating a greenhouse effect.
And according to a study published this month in the journal Environmental Research LetterContrails can cause as much warming as all of airplanes' combined carbon dioxide emissions.
So what's the solution?
The aviation industry is at a crossroads. As the world grapples with the urgent need to combat climate change, the focus has been primarily on reducing carbon emissions. But there is a ray of hope.
“The good news is that people are working hard to find ways to avoid contrails, and we may be able to reduce their impact faster than we can reduce carbon emissions,” says Dr Mark Stettler of Imperial College London, one of the study's authors. His optimistic outlook is supported by research showing that “contrail avoidance” could be a relatively quick and cost-effective means of reducing aviation's global warming contribution.
Avoiding contrails
Dr Stephen Barrett, professor of engineering at the University of Cambridge, explains that contrail avoidance is one of the most promising strategies to mitigate the effects of contrails. “CO2 is only half the climate problem for aviation, so it's vital that the industry tackles contrails as well,” he says. “Waiting for new aircraft to join the fleet is a long time, so operational measures such as contrail avoidance are a prime opportunity to do something in a shorter time frame.”
This involves changing flight paths to avoid the cooler, wet parts of the atmosphere where contrails are most likely to form. Amazingly, adjusting just 5% of flight paths could eliminate 80% of the warming caused by contrails. In other words, only 1 in 20 flights would need to fly above, under, or around areas of the sky where harmful contrails are predicted to form.
Intelligent route planning is one key strategy experts are studying. By avoiding atmospheric conditions that cause lingering contrails, airlines could significantly reduce their environmental impact. What would the cost be? Studies suggest that such adjustments would be relatively inexpensive, costing an airline an average of about $5 per flight.
Further research is underway to explore the effectiveness of contrail avoidance on a larger scale. Barrett says he and many other researchers are focused on demonstrating the approach over the next few years. If successful, these measures could be deployed on a wider scale, providing a faster way to reduce aviation's environmental impact.
Reducing soot emissions
Reducing soot emissions is another key aspect. Soot particles act as nuclei for water vapor to condense and form contrails. Designing aircraft engines that burn fuel more efficiently and produce fewer soot particles can significantly reduce the lifespan of contrails and reduce their global warming impact. Combined with intelligent route planning, this approach is a promising step towards minimizing the environmental impact of contrails.
What can you do?
As travellers, we all have a role to play in this journey towards sustainability, and while much of the change will come from the industry, there are things we can do to help boost the industry and become a more sustainable traveller overall.
Make your voice heard
Supporting airlines that prioritize contrail avoidance and lobbying for policies that address aviation's full climate impact are important steps. When asked what can be done to protect wildlife, a polar bear researcher responded, “Tell people to vote.” Supporting political candidates and policies that prioritize climate action is essential to driving needed change in aviation and beyond.
Barrett emphasizes the urgency of this approach. “We really need to move quickly to understand whether contrail avoidance is feasible at scale and demonstrate whether the benefits are realizable,” he says. “This requires public and political support.”
Fly less
Dr Edward Grispeert is a Research Fellow in the School of Natural Sciences at the Grantham Climate Change Institute. Environmental Research Letter Study author John Myers adds that while reducing contrails is important, so is flying less where possible: “For short-distance travel, particularly in Europe, rail can be a cheaper, faster and more environmentally friendly option,” he says.
Griespeert's research explores how contrails can serve as a “natural experiment” to understand how human activities affect the formation of natural cirrus clouds, which is crucial for elucidating the broader effects of human emissions on cloud properties and climate change.
Flying into the future
So what are contrails in the broader context of the global environment? These seemingly harmless white clouds in the sky are a visible reminder of the challenges and opportunities that lie ahead in the fight against climate change. As we look to the future, it's clear that every aspect of our journey matters – down to the clouds they leave in the sky. By understanding the science behind contrails and advocating for solutions, we can all contribute to a more sustainable future for aviation and the planet.
The next time you look up at the sky and see those familiar white streaks, remember: each streak tells a story — a story of exploration, progress, and the ongoing quest to balance our love of travel with our responsibility to protect the world we care for.
The mark we make today will shape the sky of tomorrow. Let's make a mark we can be proud of.
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source:
- Dr. Mark Stettler, Lecturer in Transport Environments, Department of Civil and Environmental Engineering, Imperial College London
- Dr Stephen Barrett, Professor of Engineering, University of Cambridge
- Dr Edward Grispeert, Research Fellow in the School of Natural Sciences at the Grantham Climate Change Institute
- Environmental Research Letter“Operational differences will result in longer satellite-detectable contrail life for more fuel-efficient aircraft.”
- Imperial College London: 9 things you can do to combat climate change
- Reviate: “How Contrails Form and Evolve”
- Clouds and Climate: “Are New Airplanes Harming the Climate?”