A new research has indicated that global warming is causing plants in the northern regions to lose carbon dioxide to the atmosphere rather than capturing it.
According to a report in ENN, the research looked at atmospheric carbon dioxide concentrations and CO2 held in ecosystems such as forests in the Northern Hemisphere in the past 20 years, to come to the premise.
It was earlier believed that the warming trend in the past two decades — with spring starting earlier and winter later, increasing the growing season — has increased the productivity of plants, enabling them to absorb more carbon from the atmosphere.
But, according to Piao Shilong from the Laboratory of Climate and Environmental Sciences at France's National Scientific Research Centre, who is also the lead author of the research, the earlier theory has not fully considered seasonal variation.
"In warmer autumns, the more prosperous plants may lose more carbon," Piao told ENN.
This is because in autumn, plant respiration — the process by which plants produce energy and release carbon dioxide — occurs more than photosynthesis, the process by which plants absorb carbon for growth.
"While both respiration and photosynthesis could be boosted by warmer temperatures, the lower intensity of sunshine, drier weather and plants' low sensitivity to temperatures could all contribute to respiration outstripping photosynthesis during autumn," said Piao.
In fact, the scientists found that in response to autumn warming, northern ecosystems are currently losing 90 per cent of the increased carbon dioxide that plants take up during spring.
"If future autumn warming occurs at a faster rate than in spring, the ability of northern ecosystems to sequester carbon may be diminished earlier than previously suggested," the report stated.
According to Zhang Chengyi, a scientist at the China Meteorology Administration's National Climate Centre, the study has also offered an interesting new angle on analyses of the global carbon cycling.
"But to reach the conclusion of net carbon loss in autumn needs more consideration," said Zhang. "In a gradual warming trend, the plants may adapt to the situation, taking up more carbon in autumn too," he added.