The world is abuzz with climate change - in more ways than one. Swelling waves and rising sea levels can be detected in the way the planet "hums", says an oceanographer.
Peter Bromirski, of the Scripps Institution of Oceanography at the University of California, San Diego, says that seismic listening stations provide a long-term record of how the amount of energy reaching the world's shores is changing with climate change.
Most geologists who study seismology try to eliminate background noise in their data, but a handful of researchers have started to take a closer look at it.
They have identified at least three different types of "noise", including the Earth's hum, which was first
discovered in 1998. The other two are called "microseisms" - tiny earthquakes - and have slightly different acoustic properties.