Chinese scientists have found the summer carbon uptake of the terrestrial ecosystem in the northern hemisphere has been significantly weakened by ongoing climate warming.
In other words, warmer years were associated with lower ecosystem carbon uptake -- the process of removing and capturing carbon from the atmosphere.
Observations of atmospheric carbon dioxide concentration from atmospheric monitoring stations at high latitudes provide complementary monitoring of the dynamics of carbon exchange in northern ecosystems.
Most studies of the northern hemisphere carbon cycle based on atmospheric carbon dioxide concentration have focused on spring and autumn, but the climate change impact on summer carbon cycle remains unclear.
Summer has the highest vegetation productivity, actively contributes to year-to-year variations in terrestrial carbon uptake and generally has the most favorable climatic conditions for carbon dioxide uptake, said the study published in Nature Communications.
Scientists from the Institute of Tibetan Plateau Research of Chinese Academy of Sciences used the record of atmospheric carbon dioxide concentrations to calculate the summer carbon dioxide drawdown, an indicator of summer carbon uptake, between July and August.
They found that the summer carbon uptake is significantly negatively correlated with terrestrial temperature within 50 degrees north latitude year-to-year from 1979 to 2012.
A refined analysis at the decadal scale reveals strong differences between the earlier (1979-1995) and later (1996-2012) periods, with the significant negative correlation only in the later period.
The emerging negative temperature response is primarily due to summer vegetation activities no longer positively responding to temperatures, according to the scientists.