Rising heat content of Earth’s oceans

Earth’s Sun-warmed surface radiates heat into the atmosphere. As the concentration of carbon dioxide and other greenhouse gases increases, more of that extra heat fails to escape into space. Although the trapped heat warms Earth’s lower atmosphere and land surface, more than 90% of it ends up in the ocean. How the ocean heat content (OHC) has changed over the past half century is the subject of a new study led by Lijing Cheng of the Institute of Atmospheric Physics in Beijing. Resolving OHC across time and space is challenging. Since 2005, a network of autonomous floats called Argo has continuously profiled the ocean’s temperature at depths down to 2000 m with steadily increasing spatial coverage (see the article by Karim Sabra, Bruce Cornuelle, and Bill Kuperman, Physics Today, February 2016, page 32). Before then, and even in Argo’s early years, measurements were less frequent, more sparse, and...