Tracking climate change means (among other things) tracking annual changes in global greenhouse gas emissions and the corresponding increases in the atmospheric CO2 concentration. This can get confusing, though, because there isn’t a perfect year-to-year correlation between the two.
Our CO2 emissions are released into the atmosphere, but the atmosphere interacts with other parts of Earth’s carbon cycle, which pull some CO2 out. In the short term, the two sinks that matter most are the oceans and the ecosystems on land. CO2 dissolves into seawater to maintain an equilibrium with the air, and photosynthetic organisms on land and in the oceans take in CO2. Shifting ocean currents or weather on land that affects plant growth will alter the amount of CO2 being taken out of the atmosphere.
It’s typically been thought that land ecosystems were the dominant source of this variability. But a team of researchers led by Tim DeVries at the University of California, Santa Barbara and Corinne Le Quéré at the University of East Anglia decided to investigate just how much of a role the oceans are playing.