Editor's Summary

3 January 2008

Autumn warming

An analysis of variations in atmospheric CO₂ and ecosystem CO₂ fluxes in the Northern Hemisphere shows that warmer autumns have been associated with an earlier autumn-to-winter CO₂ build-up in the atmosphere. This seems counter-intuitive: warm autumns surely imply long growing seasons and a beneficial effect on terrestrial carbon sinks as trees and plants make more biomass. An explanation is provided by satellite observations and numerical modelling. Enhanced respiration caused by higher temperatures causes carbon losses that offset photosynthetic gains, limiting the potential of these ecosystems to act as carbon sinks. And CO₂ loss due to autumn warming may offset most of the increased CO₂ uptake during spring. If future warming occurs more rapidly in autumn than in spring, the ability of northern ecosystems to sequester carbon may diminish more rapidly than previously predicted.

News and Views: Carbon cycle: Sources, sinks and seasons

Changes in the phasing of seasonal cycles of carbon dioxide in the atmosphere mark the time when a region becomes a source or a sink of CO₂. One study of such changes prompts thought-provoking conclusions.

John B. Miller

doi:10.1038/451026a

Full Text | PDF (461K)

Letter: Net carbon dioxide losses of northern ecosystems in response to autumn warming

Shilong Piao, Philippe Ciais, Pierre Friedlingstein, Philippe Peylin, Markus Reichstein, Sebastiaan Luyssaert, Hank Margolis, Jingyun Fang, Alan Barr, Anping Chen, Achim Grelle, David Y. Hollinger, Tuomas Laurila, Anders Lindroth, Andrew D. Richardson & Timo Vesala

doi:10.1038/nature06444

First paragraph | Full Text | PDF (828K) | Supplementary information