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Phoenix666 writes:

North American cold-climate forests are already absorbing less carbon, study shows:

Trees are one of humans' biggest allies in the fight against climate change, soaking up around 30% of the carbon we pump into the atmosphere by burning fossil fuel.

And over the past several decades, it has appeared that cold-climate forests at high latitudes have become even more effective carbon sinks as rising temperatures and higher CO2 levels have made them more productive.

But a new study led by University of Michigan researchers gives a clearer picture of what's happening in different regions, and it has cast additional uncertainty on whether those ecosystems will continue to absorb carbon as they become hotter and drier in the decades ahead.

Published in PNAS and involving experts from around the globe, the study shows that the amount of carbon Siberian forests contribute to the planet's seasonal carbon flux has increased much more than that of other forests at similar latitudes. Since the early 1980s, the seasonal carbon uptake in Siberian forests has increased four times more than that of North American boreal forests like those in Alaska and western Canada, for example.

The study is the first to quantify how carbon emitted from specific surface regions during the annual carbon flux affects the seasonal cycle of CO2 in the atmosphere: The planet essentially "breathes in" carbon during the spring and summer when trees and plants grow leaves and photosynthesize. It exhales in winter when vegetation goes dormant.

Knowing this seasonal flux gives researchers a picture of how productive different forest regions are and how much carbon they remove from the atmosphere.

Siberian forests are absorbing more, North American forests less.

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