There is significant evidence that northern Canada's climate has already undergone substantial change. These changes have meant significant impacts for physical, natural and human systems in Canada's North. Climate models suggest that such trends will continue into the future, and therefore shifts in Arctic systems are expected for some time to come. This introductory paper is the first in a series published in two issues of Ambio presenting work conducted for northern chapters of two recent Canadian national climate science assessment initiatives, From Impacts to Adaptation: Canada in a Changing Climate 2007 and Human Health in a Changing Climate: A Canadian Assessment of Vulnerabilities and Adaptive Capacity. Collectively, these assessments involved the work of 24 scientists with expertise in a variety of disciplines and regions in the Canadian North. These assessment processes adopted aspects of a vulnerability approach to climate assessment, primarily through a review of existing and projected exposures and elements of adaptive capacity based on existing literature. In so doing, they have contributed towards a more comprehensive understanding of climate impacts and adaptations across the northern regions of the country. This paper provides an overview and introduction to the series of papers contained in the two issues of Ambio.