HR: 08:15h
AN: PP51A-02    [PDF]
TI: Northern Hemisphere Regional Climate Change during the Last Millenium
AU: * Shindell, D T
EM: dshindell@giss.nasa.gov
AF: NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: Schmidt, G A
EM: gschmidt@giss.nasa.gov
AF: NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: Mann, M E
EM: mann@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22902 United States
AU: Miller, R L
EM: rmiller@giss.nasa.gov
AF: NASA Goddard Institute for Space Studies and Department of Applied Physics and Applied Mathematics, Columbia University, 2880 Broadway, New York, NY 10025 United States
AB: We examine the regional climate response to variability in volcanic aerosols and solar irradiance in a stratosphere-resolving general circulation model (GCM). The simulated surface temperature anomalies are compared with historical data and proxy-based reconstructions at various timescales, including a new analysis of the mean climate response pattern during the cold-season following large tropical volcanic eruptions back to the beginning of the 17th century. This anomaly pattern strongly resembles the Arctic Oscillation (AO) or Northern Annular Mode (NAM), and with our four-century record, the mean response is statistically significant over much of the Northern Hemisphere land area. The dynamical climate response to injections of volcanic aerosols into the stratosphere is well simulated in many GCMs, demonstrating the robustness of the AO/NAM surface response to stratospheric temperature and wind anomalies. Due to opposing dynamical and radiative effects, we show that the long-term (decadal and longer) regional response to volcanic eruptions is not significant compared to unforced variability for either the winter or the annual average, however. Solar variations induce shifts in the AO/NAM in a similar manner to the short-term volcanic response. In contrast to the one to two year timescales for large volcanic eruptions, solar variations can persist for decadal or longer timescales, creating a long-term regional response which greatly exceeds unforced variability. Solar forcing thus appears to have been the most important external driver of long-term regional climate anomalies during the last millennium.
DE: 0370 Volcanic effects (8409)
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
DE: 3362 Stratosphere/troposphere interactions
DE: 8409 Atmospheric effects (0370)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting