Research press release


Nature Communications

Climate science: A recent pause in atmospheric carbon dioxide growth



今回、Trevor Keenanの研究グループは、各種観測データと植生モデルを用いて、こうしたさまざまな駆動要因の収支を求めた。そしてKeenanたちは、大気中CO2濃度の上昇によって光合成(CO2吸収過程の1つ)が増えたが、全球気温の上昇傾向が鈍化したために呼吸(CO2放出過程の1つ)が減ったことを明らかにした。この2つの要因は、植物によるCO2吸収量が増え、人為的に排出され大気中に残留するCO2の占める割合が2002年から2014年の間に年約2.2%のペースで減ったことを意味している。


A pause in the growth rate of atmospheric carbon dioxide (CO2) has been observed in recent years, despite increasing emissions of CO2from human activity, reports a study published in Nature Communications this week. These findings suggest that enhanced carbon uptake from land-based vegetation has decreased the proportion of human-induced CO2 emissions that remain in the atmosphere.

While absolute atmospheric CO2 levels have been increasing since the Industrial Revolution, there is significant year-to-year variability in the rate at which this increase occurs, largely driven by annual differences in plant growth. Quantifying the changes in the rate of CO2 emissions is essential due to the role CO2 plays in driving climate change. However, these changes are difficult to assess because of the different processes that govern plant growth, especially the balance between the uptake and release of CO2.

Trevor Keenan and colleagues use observations and vegetation models to determine the balance of these driving forces. They show that increasing atmospheric CO2 has enhanced photosynthesis (a CO2 uptake process), but that a slowdown in the rise of global temperatures has also reduced respiration (which releases CO2). Both factors mean more CO2 has been taken up by plants, thereby slowing the rate of CO2accumulation in the atmosphere between 2002 and 2014 by approximately 2.2%/year.

The authors caution that the slowdown in the growth rate of atmospheric CO2 may be temporary, and that increased carbon storage by plants will not resolve the issue of climate change in light of continued increases in absolute CO2 concentrations.

doi: 10.1038/ncomms13428

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