The first summer on record that melts practically all of the Arctic's sea ice, an ominous milestone for the planet, could occur as early as 2027.

Ocean acidification close to critical threshold, say scientists, posing threat to marine ecosystems and global liveability

Industrial civilisation is close to breaching a seventh planetary boundary, and may already have crossed it, according to scientists who have compiled the latest report on the state of the world’s life-support systems.

“Ocean acidification is approaching a critical threshold”, particularly in higher-latitude regions, says the latest report on planetary boundaries. “The growing acidification poses an increasing threat to marine ecosystems.”

At a briefing outlining the findings, Levke Caesar, a climate physicist at PIK and co-author of the report, said there were two reasons the levels of ocean acidification were concerning.

“One is [that] the indicator for ocean acidification, which is the current aragonite separation state, while still being in the safe operating space, is approaching the threshold of transgressing the safe boundary,” Caesar said.

“The second is that there are actually several new studies that were published over the last years that indicate that even these current conditions may already be problematic for a variety of marine organisms, suggesting a need [to] re-evaluate which levels can actually be called safe.”

Ocean acidification was getting worse globally, with the effects most pronounced in the Southern Ocean and the Arctic Ocean, she added.