Environ. Res. Lett. 6, 044007 (2011)

Self-reinforcing processes, known as positive feedbacks, amplify climate change, and are responsible for rates of change in the Arctic being among the highest on Earth. Although the major processes involved in these feedbacks are quite well understood, it is not clear how different feedbacks interact.

Yonghua Chen of Columbia University and the Goddard Institute for Space Studies, USA, and co-workers used a climate model to investigate how the amount of thermal radiation emitted towards the surface by the Arctic atmosphere varied with changes in water vapour and cloud properties throughout the seasonal cycle, and how they are projected to increase over the twenty-first century.

The results show that the emitted thermal radiation was most sensitive to water vapour and cloud density in the winter, explaining much of why the largest amplification of surface temperature occurs during this season. The increased levels of water vapour and cloud density expected in coming decades owing to greater greenhouse-gas concentrations will weaken the feedback interaction, suggesting that the current rate of amplified warming in the Arctic, relative to the rest of the Northern Hemisphere, may be reduced in future.