The NOAA ESRL GML-Radiation program has carried out research on the effects of volcanos on climate. References to that work can be found at the bottom of this page. Following first is a brief summary of what is known about volcanic climate effects.
Benjamin Franklin was the first to suggest that major volcanic eruptions might have a significant impact on short-term climate variations great distances from the volcano. Since the early 1960's, when the first major eruption of a volcano in several decades (Agung) occurred, modern science has intensified its research into the possible effects of volcanos on weather and short-term climate.
Volcanos that pose the greatest threat are those that erupt with sufficient force and thermal structure to lift massive quantities of effluent into the stratosphere. Some of the effluent turns into small sulfuric acid droplets that remain in the stratosphere for many months, up to a few years. It is the influence of these droplets on solar and thermal radiation that can affect short-term climate. There are several ways that the volcanic droplets can influence the earth's energy budget, which in turn has the capability to force changes in the world's wind and weather patterns. Most basically, the droplets block the sun's energy from entering the lower portion of the atmosphere, or troposphere, and the warming of the earth's surface and troposphere is reduced. A lesser effect of the acid drops is to block some of the outgoing infrared radiation from the earth's surface, similar to (but physically different from) water vapor and other greenhouse gases, thus causing a slight warming. Research has shown that the cooling (reduced warming) from the blocked sunlight is a much greater influence than the enhanced warming caused by the trapping of infrared energy so that a net cooling is realized near the earth's surface, as was observed following Mt. Pinatubo (1991). The manner in which the radiative cooling is manifested around the planet is a complex set of events including changes in ocean heat storage and influences on wind patterns and precipitation events which are also simultaneously affected by many unrelated factors such that the exact influence of the volcano may be difficult to discern.
ESRL GML GRAD Publications and reports on volcanic influences
on climate:
Dutton, E. G., and J. J. DeLuisi, 1983a): Spectral extinction of direct solar
radiation by the El Chichon cloud during December 1982, Geophys. Res. Lett.
10, 1013-1016.
Dutton, E. G., and J. J. DeLuisi, 1983b): Optical thickness features of the
El Chichon stratospheric debris cloud. Proceedings 5th Conference on Atmospheric
Radiation, 31 Oct - 4 Nov 1983, Baltimore, MD.
Dutton, E. G., and J. J. DeLuisi, and B. A. Bodhaine, 1984: Features of aerosol
optical depth observed at Barrow, March 10-20, 1983, Geophys. Res. Lett.,
11, 385-388.
Dutton, E. G., and J. J. DeLuisi, 1987: Aerosol optical depth and ratios of
diffuse-sky to total solar irradiance measured from aircraft following the
eruption of El Chichon. NOAA Data Report ERL ARL-12.
Dutton, E. G., J. J. DeLuisi, and A. P., Austring: 1987. Measurement of solar
radiation at Mauna Loa Observatory 1978-1985, with emphasis on the effects
of the eruption of El Chichon. NOAA Data Rep. ERL-ARL-13.
Dutton, E. G., 1990: Comments on "Major Volcanic Eruptions and Climate:
A Critical Evaluation". J. Clim., 3, 587-588.
Dutton, E.G. and J.R. Christy, 1992: Solar Radiative Forcing at Selected Locations
and Evidence for Global Lower Tropospheric Cooling Following the Eruptions
of El Chichon and Pinatubo. Geophys. Res. Lett. 19, 2313-2316.
Dutton, E.G., 1994: Comparison of the solar radiative effects of El Chichon
and Mt. Pinatubo long-lived aerosols. Extended abstracts for AMS 8th Conference
on atmospheric Radiation, Nashville, TN, 23-28 Jan. 1984.
Dutton, E.G., and S.K. Cox, 1995: Tropospheric radiative forcing from El Chichon
and Mt. Pinatubo: Theory and observations. Paper No. 586, Dept. of
Atmospheric Science, Colorado State University, Fort Collins, Colo., 209 pp.
Dutton, E.G., 1997: Radiative forcing of El Chichon and Pinatubo eruptions
as determined from observations and radiative transfer calculations. IRS
'96: Current Problems in Atmospheric Radiation, W.L. Smith and K. Stamnes,
Eds., A. DEEPAK Publishing, Hampton, Virginia. pages 367-370.
Stone, R.S., J. Key, and E.G. Dutton,1993: Enhanced opacity of the Arctic
Stratosphere after the 1991 eruption of Mount Pinatubo. Geophys. Res. Lett.,
21, 2359-2362.
Stone, R.S., E.G. Dutton, and J.R. Key, 1994: Properties and decay of Pinatubo
aerosols in polar regions compared with tropical observations. Extended abstracts,
AMS 8th Conference on Atmospheric Radiation, Nashville, TN, 23-28 Jan. 1994.