New research has shown that the rise of carbon dioxide in the atmosphere has slowed since the start of the century, thanks in part to the increased growth of plants due to higher carbon dioxide levels in the air. Higher temperatures have also reduced the Co2 emitted by the respiration of plants. The proportion of annual carbon emissions that remain in the air has dropped from 50 percent to 40 percent in the last decade.
Unfortunately, scientists also concluded that this “greening” process is only offsetting a small portion of the carbon emissions from fossil fuels and other human activity, which amounts to billions of tons of Co2, which indicates that this greening is not enough to stop the global warming that imperils the planet.
The absolute level of carbon dioxide in the atmosphere reached levels over 400 parts per million (ppm) in 2015, alongside new record breaking temperature highs all over the world.
“Unfortunately, this increase is nowhere near enough to stop climate change,” according to Dr Trevor Keenan, from the Lawrence Berkeley National Laboratory in the US, who headed the new research. The study was published in Nature Communications by an international team of scientists.
The study says:
“Enhanced carbon uptake by the biosphere to date has slowed the growth rate of atmospheric CO2 and our results [suggest] uptake has been especially strong recently. Without effective reduction of global CO2 emissions, however, future climate change remains a stark reality.”
The report uses a range of air, land, and satellite data to investigate how the rates of carbon dioxide absorption have changed over the last few decades, using modeling to determine the factors behind the changes. From 1960 until 2000, CO2 rose at increasingly high rates every year. After 2000, the rate leveled off to roughly the same increase every year. It was not clear from the data whether the harm to plants from warming and droughts outweighs the fertilization effect of higher CO2 levels.
“The researchers make it clear that this effect is almost certainly temporary. The ‘greening’ effect of CO2 will ultimately be overwhelmed by the plants’ own respiration and decay, which will cause even more CO2 to be released,” said Professor Chris Rapley, from University College London.
Scientists also noted that this highlights the importance of preserving forests around the world.
On Tuesday, the World Meteorological Organization warned that the last five years (up to 2015) made up the hottest five-year period ever recorded. They also highlighted an increased risk of extreme weather events.