We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are about 3 Tg CH4 yr-1. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicate that CH4 emissions from wet soils will be enhanced more than consumption by dry soils of the tundra and boreal forests. As a consequence, we project that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide, CO2, and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 33 T g CO2-Eq. yr-1; that is, a balance between the net methane emissions of 69 T g CO2-Eq. yr-1 and the carbon sequestration of 10 T g C yr-1 (36 T g CO2-Eq. yr-1).