This project seeks to determine how the impact of stratospheric changes at the earth's surface is affected by model resolution, improvements in model physics and the nature of the ocean model used (dynamical versus mixed layer ocean). The PIs will examine to what extent any cooling in the North Atlantic is a feature of natural variability or forced (including ocean heat transport changes, changes in atmospheric circulation, increasing greenhouse gases and/or aerosol loadings). The PIs will (i) to quantify the importance of including stratospheric dynamics in climate change experiments and the potential for important tropospheric and oceanic feedbacks; (ii) to project (based on given scenarios) future trends in the North Atlantic surface air temperature and examine their dependence on the inclusion of the stratospheric and oceanic components; and (iii) to examine to what extent fingerprints of anthropogenic climate change are robust over all the model configurations used in the study. The NASA GISS model with finer vertical and horizontal resolution will be used. The model will also include on-line ozone chemistry and transport. This will improve the solar cycle heating effects in the stratosphere. Interannual varying SST will be used, this may help generate more realistic summer results than with the low resolution. The work is important because it will increase understanding of the role of the stratosphere in climate.
