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Model Projections of the Changes in Atmospheric Circulation and Surface Climate over North America, North Atlantic and Europe in the 21st Century

Key Findings

  • The wintertime response to climate change in the late 21st century is characterized by an enhancement of the positive phase of the North Atlantic Oscillation in sea level pressure, and pole-ward and eastward displacements of the Atlantic jet stream and storm track.
  • These circulation changes are linked to atmospheric responses to the gradient of the altered SST forcing in the North Atlantic, which is associated with weakening of the Atlantic Meridional Overturning Circulation.
  • The eddy vorticity fluxes in the perturbed storm track reinforce the response pattern to climate change.
  • In summer, the projected enhancement of convection over the eastern tropical Pacific is accompanied by a wavetrain spanning the North America-North Atlantic-Europe sector. This feature is associated with diminished storm track activity at 40°-50°N, and an eddy forcing pattern that matches well with the summertime response in the late 21st century.

Ngar-Cheung Lau, Jeffrey J. Ploshay. Journal: Journal of Climate. DOI: 10.1175/JCLI-D-13-00151.1

Summary

The impacts of climate change on the North America-North Atlantic-Europe sector are studied using a coupled general circulation model (CM3) and a high-resolution atmosphere-only model (HiRAM), both developed at the Geophysical Fluid Dynamics Laboratory. Long-term changes in surface temperature, precipitation and storminess patterns over Europe and the North Atlantic are projected.

In winter, the model experiments project a drying trend over southern Europe, and a strong warming trend over northwestern Europe, towards the end of the 21st century.

In summer, dry and warm conditions are projected over Europe within the 35°-50°N zone.

Projected trends of precipitation (upper panels) and surface air temperature (lower panels) for the winter (left panels) and summer (right panels) seasons. Results are based on simulations with the GFDL high-resolution atmospheric model (HiRAM) for the historical (1979-2008) period, and for the 2086-2095 period under the RCP8.5 climate scenario.