Nearly all of the world's oceans are already affected by climate change.

Stephanie Henson at the National Oceanography Centre in Southampton, UK, and her colleagues used climate models to analyse trends in sea-surface temperature, pH, oxygen levels and primary production (a measure of food availability for marine ecosystems) between 1860 and 2005, and to predict changes until 2100. They found that 99% of Earth's oceans are experiencing decreased pH conditions that exceed the range of natural variability. The models predicted that in the next 15 years, 55% of oceans will be affected by at least one other climate-driven factor. By 2050, this proportion is likely to increase to 86% under the high, 'business-as-usual' emissions scenario.

In the medium emissions scenario, only one-third of the oceans will be affected by multiple factors by 2030. This would give many marine ecosystems an extra 20 years to adapt to climate change.

Nature Commun. 8, 14682 (2017)