Another factor for consideration is the relative sensitivity of any activity, resource, or area of the region to climate and how these other changes and pressures will affect that sensitivity. Population growth, changing demographics, and the movement of a large proportion of that population to coastal communities are projected to increase the sensitivity of North Americans to climate change and variability. Because of inherent uncertainties in our knowledge of the processes affected, our understanding of the magnitude of the responses is equally, or more, uncertain. These uncertainties are compounded further by uncertainties about how landowners and other decision makers will respond to associated risks. Assumptions about how people will respond to risks associated with climate change can significantly affect estimates of associated socioeconomic impacts.
Differentiated impacts can occur across North America .
As this assessment notes, particular areas and sectors within North America are projected to experience negative impacts, whereas other areas and sectors could benefit from the projected changes. Similarly, because of differences in adaptive capacity within North America, different areas and sectors will be better able to respond to climate change. Climate change is a dynamic process that will occur over time. Although most of the literature on impacts, including the analysis in this assessment, has focused on a 2xCO 2 world, it is reasonable to expect that some of the kinds of impacts that have been discussed would begin to manifest themselves before atmospheric concentrations of CO 2 doubled. Many of the actions that might be taken today to address existing stresses might also help reduce vulnerability to potential climate change and variability.