Climate warming is especially pronounced in the Arctic, which has led to decreased sea-ice coverage and substantial permafrost thawing. These changes have a profound impact on the carbon cycle that directly affects the air-sea exchange of carbon dioxide (CO2), possibly leading to substantial feedback on atmospheric CO2 concentration. Several recent studies have indicated such feedback but the future quantitative impact is very uncertain. To minimize these uncertainties, there is a need for extensive field studies in order to achieve both a better process understanding as well as to detect probable trends in these processes. In this contribution, we describe a number of processes that have been reported to be impacted by climate change and suggest a coordinated international observational programme for their study.