A new study in Science used 30 years of atmospheric oxygen and carbon dioxide measurements to separate how much carbon the ocean and land absorb. It found the ocean took in an average of 2.8 billion tonnes of carbon per year from 1990 to 2019, roughly 35 percent of fossil fuel emissions, and the ocean sink strengthened by about 0.63 billion tonnes per decade. The land sink stayed flat over the same period, absorbing about 1 billion tonnes of carbon per year, and it has generally declined since peaking around 2009. The results suggest current models underestimate how much the ocean sink has strengthened and overestimate how much land ecosystems will keep absorbing as CO2 and nitrogen rise. Warmer seawater and ocean acidification could weaken the ocean sink in the future. The authors stress the need for stable funding for long-term atmospheric measurements, which are the only way to track these planet-scale changes.
