More bad news on climate change, I’m afraid. A team of scientists has completed a highly accurate assessment of ocean temperature increases based on measurements of atmospheric oxygen and carbon dioxide. The hotter the ocean gets, the more of these gases you expect to find, so these measurements act as a “whole-ocean thermometer.” Here are the results in a nutshell:

APO stands for “atmospheric partial oxygen,” and the chart shows the portion of ΔAPO that’s caused by climate change. This can then be reverse engineered to tell us how much ocean warming is caused by climate change.

Other studies have recently produced estimates of ocean warming that are higher than we previously thought, and this one provides confirmation using entirely different methods. Needless to say, this is bad news: if ocean temperature is rising faster than we thought, it means that sea level is also rising faster than we thought. This is potentially disastrous for low-lying regions like Florida, Bangladesh, and islands in the western Pacific.

But that’s not all. One of the key questions in climate change science is “sensitivity”: that is, how much temperature will rise based on a doubling of atmospheric CO 2 . This new estimate increases the lower bound from 1.5ºC to 2ºC, which in turn reduces the amount of CO 2 we can emit and still keep global warming below the target range of 2ºC above historical levels.

The odds of staying below that 2ºC target were always slim. Now they’re slimmer still unless we get serious about climate change mighty fast. So far, there’s not much sign of that happening.