Terrestrial ecosystems of high latitudes are responsible for storing a substantial proportion of global soil organic carbon. The release of carbon from soils of high latitude terrestrial ecosystems to the atmosphere has the potential to influence concentrations of carbon dioxide and methane in the atmosphere. Substantial progress has been made in representing the role of soil thermal dynamics in the seasonal exchange of carbon dioxide between high latitude ecosystems and the atmosphere. Model analyses of responses of carbon dioxide exchange to inter-annual variability in temperature exchange suggest that responses of carbon dioxide exchange depend substantially on changes in the length of the growing season and changes in soil moisture. Inter-annual responses of methane also depend substantially on responses of soil moisture, particularly changes in the water table. At decadal time scales, simulated responses of carbon dioxide and methane to warming depend substantially on the representation of carbon and nitrogen transformation in the soil and how the response of the nitrogen cycle influences the uptake of carbon by vegetation. Additional progress in predicting responses of carbon dioxide and methane of high latitude terrestrial ecosystems to future climate variability and change requires (1) better representation of spatial variability in soil moisture and water table depths, and (2) improved understanding of carbon and nitrogen transformation in soils.