HR: 09:15h
AN: PP51A-06    [PDF]
TI: Solar vs. Anthropogenic Forcing During the Maunder Minimum
AU: * Rind, D
EM: drind@giss.nasa.gov
AF: NASA/Goddard Institute for Space Studies at Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: Lonergan, P
EM: plonergan@giss.nasa.gov
AF: NASA/Goddard Institute for Space Studies at Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: Lean, J
EM: jlean@ssd5.nrl.navy.mil
AF: Naval Research Laboratories, Code 7376L, Washgton, DC 20375 United States
AU: Shindell, D
EM: dshindell@giss.nasa.gov
AF: NASA/Goddard Institute for Space Studies at Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: Perlwitz, J
EM: judith@giss.nasa.gov
AF: NASA/Goddard Institute for Space Studies at Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: Lerner, J
EM: jlerner@giss.nasa.gov
AF: NASA/Goddard Institute for Space Studies at Columbia University, 2880 Broadway, New York, NY 10025 United States
AU: McLinden, C
EM: chris.mclinden@ec.gc.ca
AF: Meteorological Serivce of Canada, 4905 Dufferin Street, Downsview, Ont M3H5T4 Canada
AB: A series of ensemble GCM experiments have been run comparing the impact of solar and anthropogenic forcing for the past 500 years. Simulations include spectrally-differentiated solar irradiance changes, a full stratosphere, and stratospheric ozone response. The results show that using a spectral vs constant wavelength change in solar forcing does not alter the overall magnitude of tropospheric cooling, although with the uniform spectral reduction there was a larger tropical response, and less stratospheric cooling. Reduced solar UV led to stratospheric ozone reduction compared to today with both the current day and pre-industrial background; however, the preindustrial composition produced stratospheric ozone increases, which led to an over total ozone increase, even during the Maunder Minimum. Using an alternate ozone photochemistry scheme (Linoz) in a higher resolution model resulted in qualitatively similar responses except that the preindustrial composition effect was somewhat smaller. The ozone changes did not have much influence on tropospheric climate, although there was some effect on high latitude pressure/height indices. With the magnitudes employed here (-0.68Wm-2 solar; -1.9Wm-2 anthropogenic) trace gas/aerosol changes produced twice as much cooling relative to today as the solar irradiance change. The cooling was much larger than that estimated in some recent temperature reconstructions, and in particular the tropical response was much larger. The NAO/AO phases were more negative with either the anthropogenic or solar-induced cooling, influenced by a reduction in the Hadley Cell intensity, and therefore do not appear to strongly discriminate between them (despite some ozone change influence). Precipitation changes followed the Hadley Cell and NAO effects, so likewise responded in a qualitatively similar manner to the two forcings. A full stratosphere was necessary to produce the negative NAO/AO response unless the cooling was sufficiently large.
DE: 0340 Middle atmosphere--composition and chemistry
DE: 1620 Climate dynamics (3309)
DE: 1650 Solar variability
DE: 3344 Paleoclimatology
DE: 3362 Stratosphere/troposphere interactions
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting