Airplane Contrails Have Surprising Effect on the Atmosphere

The climate impact of flying isn’t just about carbon emissions. The contrails that airplanes create also influence the temperature of our atmosphere—and a new study finds that impact is set to grow in a big way.

As planes cruise through the upper reaches of the troposphere. spewing exhaust, they also leave behind trails of water vapor that can form streaky cirrus clouds. Most of these contrail cirrus clouds dissipate quickly, but under the right conditions they can linger for hours, and when that happens they warm the atmosphere by absorbing thermal radiation emitted by the Earth.

Scientists have known about the greenhouse effect of contrail cirrus for years—in fact, there’s an entire niche field of research devoted to it. And it’s important: Globally, the atmospheric warming associated with these clouds is estimated to be larger than that caused by aviation’s carbon emissions. That surprising fact has some scientists curious about whether the effect will grow as the skies continue to get more trafficked into the future.

Now, a pair of researchers from the German Aerospace Center (DLR) has attempted to answer that question. Using a previously developed climate model that includes contrail cirrus clouds and an aviation emissions database developed by the U.S. Department of Transportation (which projects future air traffic out to mid-century), the authors looked at how the atmospheric warming effect of contrails will change. Their findings, published today in Atmospheric Chemistry and Physics, show that by 2050, contrail-induced warming could be three times higher than it was in 2006. In fact, this type of warming will likely outpace warming from rising carbon dioxide emissions, thanks to concurrent improvements in fuel efficiency.

Senior study author Ulrike Burkhardt of the DLR wasn’t too surprised by the results, noting that air traffic itself is projected to increase fourfold over the same time period. “It’s incredible how air traffic is increasing,” Burkhardt told Earther. She added that the expected rise in contrail cirrus warming is also, partly, due to modern planes flying slightly higher than their predecessors, which is likely to lead to more contrail cloud formation over the tropics.

Now, this effect is by no means a planetary catastrophe. The authors’ models indicate cirrus clouds will contribute some 160 milliwatts of additional ‘radiative forcing’—extra energy flowing back toward the Earth’s surface— by mid-century. Ethan Coffel, an atmospheric scientist at Dartmouth College who wasn’t involved with the paper, noted that for comparison, under the climate change scenario the authors use, heating from greenhouse gas emissions will be around 6,000 milliwatts per square meter by the end of the century.

“So while the contrail forcing is certainly significant, it’s a relatively small contributor to overall warming,” Coffel told Earther via email.

The warming effect of cirrus clouds is also a short-lived, and because it occurs in the upper atmosphere, it’s not clear how much of a difference it actually makes for temperatures at Earth’s surface, something Burkhardt called an “open research topic.” Regardless, it’s an important effect to understand, in part because there are obvious ways to mitigate it.

Tightening pollution controls to reduce the number of soot particles airplanes spew would help decrease the amount of water vapor condensing in their wake. However, soot would have to be decreased a lot to have a significant effect—even if it was reduced by 90 percent, the authors’ models show contrail cirrus clouds producing more warming in 2050 than they did in 2006. Ultimately, the best option for reducing this effect and aviation’s carbon footprint is to fly less.

As a final note to head off anyone planning to take this study wildly out of context: Airplane contrails are not part of a secret government plot to control your behavior or the weather, or to sterilize the population. They never were. And yes, there’s actually research to back that up.


more recommended stories

  • Now-Tropical Depression Barry Mostly Spares New Orleans, But Flood Risk Remains High

    Barry Williams wading through storm surge.

  • Your Binge-Watching of Netflix and Porn Is Contributing to Millions of Tons of Emissions a Year

    Most days when I get home.

  • A Blackbird Blowing ‘Smoke’ Rings Wins Top Prize at the 2019 Audubon Photography Awards

    Whoa.Photo: Kathrin Swoboda (Audobon Photography Awards).

  • Paradise, California, Has Lost More Than 90 Percent of Its Residents Since Last Year’s Deadly Fire

    The remnants of the deadly Camp.

  • The Science Behind Tropical Storm Barry’s Potentially Catastrophic Flooding

    Photo: AP If there is one.

  • New Orleans Faces Major Flooding From Tropical Storm Barry

    Terrian Jones feels something move in.

  • Russian Coal Plant Tells Instagrammers to Please Stop Taking Selfies in Its Pollution-Filled Waste Dump

    The turquoise water of a lake.

  • AOC and Bernie Sanders Are Asking Congress to Declare a Climate Emergency

    Photo: AP Governments declaring climate emergencies.

  • That Big California Earthquake Left a Scar That’s Visible From Space

    Friday’s magnitude 7.1 earthquake near Ridgecrest,.

  • It’s Raining Inside the Metro as Flash Floods Rage Across Washington DC

    Washington, D.C. commuters came back to.

  • Austria on the Verge of Becoming First EU Country to Ban Controversial Roundup Herbicide

    A popular herbicide currently in use.

  • Magnitude 7.1 Earthquake in Southern California Is Second Major Quake in Two Days

    A liquor store in Ridgecrest, California.

  • How to Keep Your Home Cool Without Wrecking the Planet

    Summertime is officially here, baby. You.

  • The Weather Machine Reveals How the Forecast Is Made—and Why It’s Now Threatened

    Photo: AP The weather forecast is.

  • Calculation Shows We Could Add a U.S.-Sized Forest to the Planet to Fight Climate Change

    Photo: Getty Trees are good for.

  • More Than a Million Ordered to Evacuate as Southern Japan Braces for a Month of Rain in a Single Day

    The fallout from last year’s floods.

  • Last Month Was the Hottest June Ever Recorded, European Satellite Data Shows

    Photo: AP The planetary heat bender.

  • Meet the People Risking Their Lives to Study Our Dying Mountain Glaciers

    Extreme Field WorkA series about how.

  • Alaska Is Hot and on Fire

    Smoky haze from a wildfire on.

  • Everyone Flopped on Climate Change During the First Democratic Debates

    Raise your hand if you want.

  • Scientists Find Dozens of Lakes Buried Far Below Greenland’s Ice

    Meltwater forms on top of the.

  • France Just Obliterated Its All-Time Heat Record

    Image: NASA WorldView France has never.

  • Wildfire Explodes in Spain as Europe Reels From Record Heat

    A burned landscape in Torre de.

  • The Gateway Protecting the Arctic’s Oldest Sea Ice Has Collapsed Months Ahead of Schedule

    The Nares Strait, open for business.

  • Big Little Lies Asks Whether Some Kids Are Too Young to Learn About Climate Change

    Following the incident, the school held.

  • Longest Oil Spill in U.S. History May Be 900 Times Larger Than Originally Estimated

    This March 31, 2015, aerial file.

  • A Potentially Record Setting Heat Wave Is About to Scorch Europe

    Photo: AP Last year’s climate change-fueled.

  • City Dwellers Could Be Key to Saving Monarch Butterflies From Extinction

    Monarchs in Chicago!Photo: Abigail Derby Lewis.

  • Researchers Discover Giant Freshwater Aquifer off U.S. East Coast

    The south shore of Martha’s Vineyard..

  • A Strange New Blend of Rock and Plastic Is Forming on a Portuguese Island

    “Plasticrust” sticking to rocks on the.

  • Why Chennai, India’s Sixth Biggest City, Has Run Out of Water

    Satellite imagery showing Chennai’s Lake Puzhal,.

  • Oregon State Police Are Searching for Republican Lawmakers Afraid of Voting on Climate Policy

    No Republican lawmakers here.Photo: Oregon DOT.