AEROSOLS AND VOLCANIC ERUPTIONS: Shading of Earth's surface

CHRONOLOGICAL SCALE
109 106 103 102 10 YR
    VOLCANIC 2 2 1
GEOGRAPHICAL SCALE
  Local  Regional  Global 
    VOLCANIC 1 2


An alternative to Solar variability and CO2 as a cause of historic and late-Holocene climate change. Chronology as good as CO2, worse than sunspots & 14C

1. Single Events: eruption large enough to produce wide-spread ash may be large enough to have climatic effects for 2 - 3 yrs
    Examples:
  • Krakatau 1883, 0.5oC cooling
  • Few eruptions in 1930-40's or 1950-60's warm periods
  • El Chichon (1982, 7x104 m tons H2SO4) no cooling, coincided with El Niño
    (Mass and Portman, 1989, Science 245:127)
  • Mt. Pinatubo (1991-92) 3 x 1011 g SO2 0.5 oC cooling

Proxy Records

TREE RING Volcano-Climate Record
Frost Rings (LaMarche and Hoerschbeck, 1984) and narrow rings (Scuderi, 1990) in western Great Basin (Ireland, Baille & Munro, 1988) correlate with Eruptions
EXAMPLE: Santorini 1628-1626 B.C., -5oC cooling in growing season
     Misidentified! in ice core Keenan, 2003

ICE CORE acidity profiles in ice cores: silicates settle out rapidly (<10 yr), but SO4 remains in atmosphere, reflecting short wave radiation, acidity apparent in ice cores (Hammer et al., 1980)


2. Changing FREQUENCY of eruptions

Examples: volcanic glass in Antarctic Ice Cores from (Gow &Williams, 1971)
Other Particles (not volcanic) abundant in DOME C (Petit et al., 1981)
Eruption frequency during Holocene correlated with climatic change (Bryson and Goodman, 1980)


DVI

The DUST VEIL INDEX (H.H. Lamb, 1970, 1977, 1983)
comparison value: Krakatau DVI = 1000



VEI

The VOLCANIC EMISIVITY (& Explosivity) INDEX

GVI: Glaciological Volcanic Index
ICE CORE ACIDITY: sulfuric acid aerosols, small particles, long residence, high reflectance
Ice cores have the best-dated record: BUT, they are biased toward polar eruptions, records vary among cores, alkaline aerosols of some eruptions neutralize signal.


NON-VOLCANIC AEROSOLS

 Satellite Images China Sahara



Solar interception by smoke
courtesy Leslie McCluskey, Oct. '03
2002 Rodeo Fire Pinedale Az Sun through smoke 2002 Rodeo Fire Haze 100 mi downwind Canyon de Chelle


Climate Aerosols Readings

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