Seminar by Dr. Qianlai Zhuang-CANCELLED

Institute of Atmospheric Sciences, South Dakota School of Mines and Technology
Climate change is expected to alter a number of large-scale processes, such as the permafrost degradation, fire disturbance and vegetation redistribution, in terrestrial ecosystems of the northern high latitudes (> 45oN). Alterations in these processes will affect the net fluxes of carbon dioxide (CO2) and methane (CH4) between the land and the atmosphere, although the magnitude of these effects is uncertain. I have developed and used a process-based biogeochemistry model, which includes explicit considerations of these large-scale processes, to estimate the greenhouse gas budget of the region for current climate conditions and for future scenarios that include changes in climate and atmospheric CO2 concentrations. The simulations indicate that, the major uncertainties in the estimates of greenhouse gas budgets arise from the effects of fire disturbances and CO2 fertilization. The simulations show that currently the region is a net source of greenhouse gases to the atmosphere, equivalent to 2.1 Pg CO2 yr-1, due largely to CH4 emissions from wet soils of the Arctic and CO2 emissions associated with fires in boreal woodlands and forests. Throughout the 21st century, the region will continue as a net source of carbon-based greenhouse gases, with a cumulative release over the 100 years of between 94 and 215 Pg CO2–equivalents (CO2-eq.). This occurs because the enhanced CH4 emissions from wetlands and CO2 releases associated with fire overwhelm the carbon uptake by vegetation. These large greenhouse gas sources will create a positive feedback to the climate system. The policy implications of this study are clear. The release of CO2 and CH4 through natural processes that have been accelerated by climate change may force earlier and larger reductions in greenhouse-gas emissions from anthropogenic activities such as the burning of fossil fuels.