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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 12, 1657, doi:10.1029/2003GL016875, 2003

A monthly and latitudinally varying volcanic forcing dataset in simulations of 20th century climate

Caspar M. Ammann

Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA


Gerald A. Meehl

Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA


Warren M. Washington

Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA


Charles S. Zender

Department of Earth System Science, University of California, Irvine, California, USA


Abstract

A new monthly volcanic forcing dataset is included in a coupled GCM for a more physically consistent treatment of the stratospheric sulfate aerosol history from explosive volcanism. The volcanic forcing is different from previous versions in that there is an individual evolution of the aerosol for each event. Thus the seasonal and latitudinal dependence of the volcanic aerosol can affect global climate in a more realistic way prior to the satellite period, compared to earlier volcanic forcing datasets. Negative radiative forcing from volcanic activity is greatest in the early 20th century prior to 1915 and in the late 20th century after 1960. The combination of volcanic and solar forcing contributes to an early-20th century warming, followed by relative cooling in late 20th century. Consequently, the addition of natural forcing factors to the anthropogenic GHG forcing in late 20th century is required to simulate the observed late 20th century warming.

Received 4 January 2003; accepted 23 May 2003; published 28 June 2003.

Index Terms: 0370 Atmospheric Composition and Structure: Volcanic effects (8409); 1620 Global Change: Climate dynamics (3309); 1704 History of Geophysics: Atmospheric sciences; 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation.

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Citation: Ammann, C. M., G. A. Meehl, W. M. Washington, and C. S. Zender (2003), A monthly and latitudinally varying volcanic forcing dataset in simulations of 20th century climate, Geophys. Res. Lett., 30(12), 1657, doi:10.1029/2003GL016875.