If you look at a map of lightning near the Port of Singapore, you'll notice an odd streak of intense lightning activity right over the busiest shipping lane in the world. As it turns out, the lightning really is responding to the ships, or rather the tiny particles they emit. Using data from a global lightning detection network, my colleagues and I have been studying how exhaust plumes from ships are associated with an increase in the frequency of lightning. For decades, ship emissions steadily...