A map showing pollution caused by ships

For many years now, scientists have used satellites to chronicle "ship tracks" — bright and easily visible atmosphere-bound emissions similar to the vapor trails produced by airplanes. But ships also emit a less obvious signature, one that's not so easy to see. As data from the Dutch and Finnish-built Ozone Monitoring… » 2/12/13 4:00pm 2/12/13 4:00pm