A global effort to track ocean acidification has begun to take shape, as researchers this week made plans to set up an international network of monitoring stations.

The seas absorb roughly one-quarter of the carbon dioxide emitted into the atmosphere each year. This makes the water more acidic, and can affect sea creatures, even weakening the calcium carbonate shells or skeletons of organisms such as corals, oysters and some types of marine plankton.

Researchers estimate that ocean acidity has risen by about 30% since the Industrial Revolution in the nineteenth century, but they need better data to improve assessments of where the problem is most severe, and to model future trends.

Much of what is known about acidification comes from a handful of open-ocean sites that scientists have returned to monthly for the past few decades, and from research cruises that span the globe. “It’s a very expensive way to do monitoring,” says Richard Feely, an oceanographer at the US National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle, Washington.

Feely helped to organize a meeting in Seattle on 26–28 June, involving oceanographers from more than 20 countries. They developed plans to build on existing observation networks, giving buoys and other monitoring devices the ability to make standardized acidification measurements. The group also plans to make acidification monitoring a routine part of ship-based measurements both on planned research cruises and private "ships of opportunity".

“What we’re trying to do is set up a large number of sites that have automated moorings that transmit back to researchers via satellite, and to use that data to verify models of ocean acidification,” says Feely. The group hopes that the number of monitoring sites can be increased from 20 to 60 in the next ten years. Each country will support its own acidification monitoring, so the expansion is contingent on national funding decisions.