Vegetation has sucked up more carbon dioxide from the air in recent years, causing the rate of C02 accumulation in the atmosphere to level off since 2002, scientists determined in research published this week in the journal Nature Communications.
While human activity remains responsible for growing amounts of carbon emissions, and the full-year atmospheric concentration of C02 in 2015 spiked above 400 parts per million, the rate of increase from 2002 to 2014 remained flat at 1.9 parts per million annually. There was also a roughly 20 percent drop in the proportion of annual carbon dioxide output from human activity that stays in the atmosphere, according to a press release from the Department of Energy’s Lawrence Berkeley National Laboratory in California.
This results from a spike in photosynthetic activity on Earth, pushed by increasing carbon dioxide levels from fossil fuel emissions, the release says. “It’s a snowball effect: as C02 levels rise in the atmosphere, photosynthetic activity flourishes and plants take in more carbon, sparking more plant growth, more photosynthesis, and more carbon uptake.”
Plant respiration also plays a part, the lab said. “Plant respiration, a process in which plants use oxygen and produce CO2, did not increase as quickly as photosynthesis in recent years,” according to the release. “This is because plant respiration is sensitive to temperature, and it was affected by the recent slowdown in global warming that was observed most significantly over vegetated land. So, between 2002 and 2014, plants took in more CO2 through photosynthesis, but did not “exhale” more CO2 into the atmosphere through respiration.”
Trevor Keenan, a scientist at the laboratory’s Climate & Ecosystem Sciences Division, led the research team.