Mt. Pinatubo

Similar heterogeneous reactions also can occur, but somewhat less efticientiy, in the lower stratosphere on global sulfate clouds (ie, aerosols of sulfuric acid), which are formed by oxidation of SO2 and COS from volcanic and biological activity, respectively (80). The effect is most pronounced in the colder regions of the stratosphere at high latitudes. Indeed, the sulfate aerosols resulting from emptions of El Chicon in 1982 and Mt. Pinatubo in 1991 have been impHcated in subsequent reduced ozone concentrations (85). 

Chandra, S., Changes in Stratospheric Ozone and Temperature Due to the Eruptions of Mt. Pinatubo, Geophys. Res. Lett., 20, 33-36 (f993). 

Fiocco, G., D. Fua, and G. Visconti, Eds., The Effects of Mt. Pinatubo Eruption on the Atmosphere and Climate, NATO ASI Series Volume 42, Subseries I, Global Environmental Change, Springer-Verlag, Berlin/New York, 1996. 

Dlugokencky, E. J., E. G. Dutton, P. C. Novelli, P. P. Tans, K. A. Masarie, K. O. Lantz, and S. Madronich, Changes in CH4 and CO Growth Rates after the Eruption of Mt. Pinatubo and Their Link with Changes in Tropical Tropospheric UV Flux, Geophys. Res. Lett, 23, 2761-2764 (1996). 

Figure 9 shows LUT-retrieved seasonal averages of aerosol volume density V as a function of altitude and latitude from winter 1990 to fall 1994. Tropical values of aerosol volume near 25 km span nearly two orders of magnitude from three months before to three months after the June 1991 eruption of Mt. Pinatubo. Retrieved values of V range from approximately 0.06 pm2cm 3 near 25 km in spring 1991 to 8 pm2cm 3 in fall 1991... 

Other gases released in volcanic explosions include the oxides, sulfides, and chlorides of carbon, sulfur, hydrogen, chlorine, and fluorine. These include C02, CO, S02, SO3, H2, H2S, Cl2, HC1, and F2. It is estimated that the eruption of Mt. Pinatubo in the Philippines on June 15, 1991 released about 1.8 x 1010 kg of gases and ash into the atmosphere. 

Hoff R. M. (1992) Differential SO2 column measurements of the Mt. Pinatubo volcanic plume. Geophys. Res. Lett. 19, 175-178. 

Read W. G., Froidevaux L., and Waters J. W. (1993) Microwave limb sounder measurements of stratospheric SO2 from the Mt. Pinatubo eruption. Geophys. Res. Lett. 20, 1299-1302. 

Soden B. J., Wetherald R. T., Stenchikov G. L., and Robock A. (2002) Global cooling following the eruption of Mt. Pinatubo a test of chmate feedback by water vapor. Science 296, 727-730. 

Hammer J. E., Cashman K. V., Hoblitt R. P., and Newman S. (1999) Degassing and miCTohte crystahization during pre-chmactic events of the 1991 eruption of Mt. Pinatubo, Philippines. Bull. Volcanol. 60, 355—380. 

During periods of intense volcanic activity large quantities of SO2 can be injected into the stratosphere, increasing the concentration of sulfate aerosols. In 1991 Mt. Pinatubo, in the Philippines, injected some 20 Tg of SO2 into the stratosphere. Under normal conditions aerosol sulfate concentrations are 1-10 particles cm , although after eruptions this can rise by as much as two orders of magnimde. Peak sulfate levels in the lunge layer can increase from around 0.1p,gm to 40 p,g m. The sulfate layer appears to take about six months to form through the slow oxidation of SO2 into a sulfate aerosol. 

One of the first comprehensive estimates of global mean, near-surface temperature over the earth s lands and oceans was reported in 1986 (Jones et al, 1986). The data showed a long-timescale warming trend. The three warmest years were 1980, 1981, and 1983, and five of the nine warmest years in the entire 124-year record up to 1984 were found to have occurred after 1978. It was apparent from this study that over this period, annual mean temperature increased by about 0.6 to 0.7°C, and that about 40 to 50% of this increase occurred since about 1975. According to many analysts, the warmest year on record up to 1995 is 1995, and recent years have been the warmest since 1860 despite the cooling effect of the volcanic eruption of Mt. Pinatubo in 1991... 

Figure J. 28. Globally averaged infrared radiative relaxation time deduced from data provided by UARS and LIMS. Note the increase in the lower stratospheric relaxation time in response to enhanced aerosol load after the eruption of Mt. Pinatubo (UARS measurements). From Mlynczak et al. (1999).

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