The Impacts of Climate Change on Autumn North Atlantic Midlatitude Cyclones

Abstract

This study explores how midlatitude extratropical cyclone intensities, frequencies, and tracks can be modified under warming-induced conditions due to enhanced greenhouse gas (GHG) concentrations. Simulations were performed with the Canadian mesoscale compressible community (MC2) model driven by control and high CO2 climate estimates from the Canadian Climate Centre model, the Second Generation Coupled Global Climate Model (CGCM2). CGCM2 simulations have effective CO2 concentration forcing, following the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario conditions, which define a near doubling of CO2 concentrations by 2050 compared to the 1980s. The control and high CO2 conditions were obtained from years 1975?94 and 2040?59 of CGCM2 simulations. For the northwest Atlantic, the CO2-induced warming for this period (2040?59) varies from ?1°?2°C in the subtropics, near the main development region for Atlantic hurricanes, to ?1°C in the north. In simulations of northwest Atlantic storms, the net impact of this enhanced CO2 scenario is to cause storms to increase in radius, with marginal tendencies to become more severe and to propagate faster (although not statistically significant), and for the mean storm tracks to shift slightly poleward.