Carbon balance: Autumn warming boosts carbon loss

A warm spring in the Northern Hemisphere means that plants absorb more carbon as their growing season gets off to an early start, but what happens as autumn becomes steadily warmer as well? Not what you might expect, although a balmy autumn allows plants’ greenery to flourish for longer, carbon uptake tails off and instead escapes into the atmosphere as carbon dioxide.

Shilong Piao and colleagues found a trend over the past twenty years towards an earlier autumn-to-winter build-up of carbon dioxide in northern ecosystems, suggesting that the period of net carbon uptake is becoming shorter. They use satellite observations of vegetation greenery and biosphere modelling to explain this response to autumnal warming: although plants’ respiration (emitting carbon dioxide) and photosynthesis (storing carbon dioxide) are both stepped up, the former outstrips the latter to give a net loss of carbon.

What’s more, this loss may offset much of the increased uptake of carbon dioxide during spring. Eastern Asia and North America are both experiencing strong autumn warming, which may account for Eurasia’s larger carbon sink, suggest the authors.

CONTACT
Shilong Piao (Laboratoire des Sciences du Climat et de l'Environnement, CEA/CNRS, Paris, France)
Tel: +33 1 6908 3876; Tel: slpiao@lsce.ipsl.fr

John Miller (National Oceanic and Atmospheric Administration, Boulder, CO, USA) N&V Author
Tel: +1 303 497 7739; E-mail: john.b.miller@noaa.gov