Pacific Ocean Crisscross Clouds Reveal the Human Imprint

By Tom Yulsman | December 23, 2013 2:23 pm

Image of the Day:

Ship tracks Aqua satellite crisscross clouds

The Pacific Ocean off California, as seen by NASA’s Aqua satellite on Dec. 22, 2013. (Source: NASA)

They may look like jet contrails, but the crisscross clouds in the image above actually were left by ships making way in the Pacific Ocean off the coast of California.

Clouds like this form when little droplets of atmospheric water vapor condense around tiny pollution particles in ship exhaust. These droplets are smaller and more numerous than those in natural clouds, which means there are more surfaces to reflect sunlight. As a result, these cloudy ship tracks are brighter than natural clouds.

While the crisscross clouds may look beautiful from space, they are actually indicative of a serious problem.

Commercial ships around the world spew nearly half as much particulate pollutants into the air as all the cars in the world, according to research by scientists at the National Oceanic and Atmospheric Administration and the University of Colorado. (For a press release about the research, go here. For the actual paper, click here.)

More than 70 percent of ship traffic takes place within 250 miles of the coastline. That concentration of shipping creates health concerns for local coastal cities and towns.

Shipping density map crisscross clouds

The density of shipping around the globe, with darker reds indicative of more traffic. (Map: Grolltech/Wikimedia Commons)

Particulate pollution isn’t the only issue. Ships emit about twice as much carbon dioxide into the atmosphere as do airplanes, thereby contributing to global warming. And those emissions could rise significantly in the next decade or so, thanks to growing world trade.

For other images of ship tracks as seen from space, check out this post at NASA’s Earth Observatory.

  • Uncle Al

    Have the UN ban all ocean traffic that is not under sail or nuclear. Ships will then emit ZERO carbon dioxide, water vapor, and particulates – with no footnotes (re battery power charged by burning coal). Who cares how many people starve and what national economies are trashed? The tenebrous future will be saved – and not for future peoples’ use, either.

    “Quis custodiet ipsos custodes?” Entropy. How do we recognize evil? We give it power. The world will not end in fire or ice. It will suffocate in malignant self-righteousness.

    • disqus_atlq8Zmtsd

      Tom is very responsible about acknowledging problems, posting proposed solutions, and addressing the problems associated with implementing them.

      He and I have some differing views, but he is worthy of respect and thoughtful discussion.

      • Tom Yulsman

        Many thanks for your comments!

        Concerning “Uncle Al’s” comments, they are fairly typical of folks with strong tribal affinities — and I honestly don’t take them very seriously. Rather than actually read the words that are written and try to engage with the writer in an open and honest way, a tribalist like “Uncle Al” reads things that he wants to be there (but are not actually there) — because doing so reinforces his tribal cred and sense of total superiority over the poor idiots who have a different point of view.

        • BlameTheBird

          Shame that such “tribalness” has become so popular as of late.

    • whatgoeson

      Just ban everything. Shut down the power grid, take all the cars and trucks off the road. Economic collapse will soon follow, thus precluding the need to send ships anywhere. No money, no commerce, no shipping…clean air, though. Well, until the cities burn…

  • explorex

    I don’t understand how the exhaust of slow moving ships can avoid dispersion long enough to be so lengthy.

    • BlameTheBird

      I grew up near Cape Kennedy, and on rare occasions, I remember seeing the plume from a rocket launch hang in the air all afternoon without major dispersion, although it does seem mystifying.



ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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