Scientists at Columbia’s Lamont-Doherty Earth Observatory have released the first year-by-year accounting of how much carbon dioxide the oceans, which act as a sink for CO₂, have absorbed during the industrial era, which suggests the sea is struggling to keep up with rising emissions.

The study, appearing in this week’s issue of the journal Nature, estimates that the oceans last year took up a record 2.3 billion tons of CO₂ produced from burning of fossil fuels. But with overall emissions growing rapidly, the proportion of fossil fuel emissions absorbed by the oceans since 2000 may have declined by as much as 10 percent.