The ability of forests to soak up man-made carbon dioxide is weakening, according to an analysis of two decades of data from more than 30 sites in the frozen north.
The finding published is crucial, because it means that more of the CO2 we release will end up affecting the climate in the atmosphere rather than being safely locked away in trees or soil.
The results may partly explain recent studies suggesting that the amount of CO2 in the atmosphere is increasing faster than expected. If higher temperatures mean less carbon is soaked up by plants and microbes, global warming will accelerate.
The Intergovernmental Panel on Climate Change, which shared the Nobel peace prize with Al Gore, has concluded that humanity has eight years left to prevent the worst effects of global warming.
Carbon uptake by land and sea is crucial to predictions about future warming. "We are currently getting a 50% discount on the climatic impact of our fossil fuel emissions," the climate scientist John Miller of the University of Colorado wrote in a commentary on the research in the journal Nature - meaning that half of what we put out is sucked up by the oceans and ecosystems on land.