The ocean plays an important role in regulating the amount of carbon dioxide in the atmosphere. As atmospheric concentrations of carbon dioxide rise (see the Atmospheric Concentrations of Greenhouse Gases indicator on p. 16), the ocean absorbs more carbon dioxide. Because of the slow mixing time between surface waters and deeper waters, it can take hundreds to thousands of years to establish this balance. Over the past 250 years, oceans have absorbed approximately 40 percent of the carbon dioxide produced by human activities.

NOAA hosts newly released surface ocean CO2 data
NOAA’s Ocean Carbon Acidification Data System (OCADS) now includes the 2025 version of the Surface Ocean CO2 Atlas (SOCAT) database.