Earth’s oceans, forests and other ecosystems continue to soak up about half the carbon dioxide emitted into the atmosphere by human activities, even as those emissions have increased, according to a study by University of Colorado and NOAA scientists published August 1 in the journal Nature.
Carbon dioxide is emitted into the atmosphere mainly by fossil fuel combustion but also by forest fires and some natural processes. The gas can also be pulled out of the atmosphere into the tissues of growing plants or absorbed by the waters of Earth’s oceans. A series of recent studies suggested that natural sinks of carbon dioxide might no longer be keeping up with the increasing rate of emissions. If that were to happen, it would cause a faster-than-expected rise in atmospheric carbon dioxide and projected climate change impacts.
Ballantyne, Tans and their colleagues saw no faster-than-expected rise, however. Their estimate showed that overall, oceans and natural ecosystems continue to pull about half of people’s carbon dioxide emissions out of the atmosphere. Since emissions of CO2 have increased substantially since 1960, Ballantyne said, “Earth is taking up twice as much CO2 today as it was 50 years ago.”
The rest continues to accumulate in the atmosphere, where it is likely to accelerate global warming.
This new global analysis makes it clear that scientists do not yet understand well enough the processes by which ecosystems of the world are removing CO2 from the atmosphere, or the relative importance of possible sinks: regrowing forests on different continents, for example, or changing absorption of carbon dioxide by various ocean regions.