Global Warming Causes

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early 1960s (Mitchell, 1961). It was probably not until 1970, when Hubert Lamb published his seminal paper 'Volcanic dust in the atmosphere, with a chronology and assessment of its meteorological significance', that the notion that volcanic eruptions could have a major influence on climate and weather became widely accepted. A plethora of papers followed that looked in some detail at the likely nature of links between volcanic eruptions, weather and climate, including Toon and Pollack (1980), Robock (1989) and Kondratyev and Galindo (1997). Research and publication in the field was further stimulated in the 1980s and 1990s following the El Chichon and Pinatubo explosive eruptions, both of which had a measurable effect on global temperatures. The eruptions coincided fortuitously with the realisation that the satellite-based Total Ozone Mapping Spectrometer (TOMS) was also capable of monitoring atmospheric sulphur dioxide, so permitting its use in estimating the mass of volcanogenic S02 injected into the stratosphere and the global tracking of S02 clouds from the eruptions (e.g. Bluth et al., 1992; Robock and Matson, 1983). Following intense El Nino-Southern Oscillation (ENSO) events after both the El Chichon and Pinatubo eruptions, speculation arose concerning a possible causal link between the eruptions and the climatic signal. A number of studies (e.g. Robock et al., 1995; Self et al., 1997) have since, however, revealed that the sea surface warming associated with the ENSO had already started prior to both eruptions. Most recently, interest has focused on the potentially far-reaching impact on the global environment of infrequent but devastating super-eruptions (e.g. Chesner et al., 1991) capable of ejecting sufficient volumes of sulphur gases into the stratosphere to trigger severe global temperature falls (e.g. Rampino and Self, 1992, 1993a; Bekki et al., 1996; Zielinski et al, 1996).

Figure 5.1 The 1991 eruption of Pinatubo in the Philippines ejected 20 million tons of S02 into the stratosphere, sufficient temporarily to reduce global surface temperatures by almost half a degree Celsius. (Image courtesy of USGS/Cascades Volcano Observatory)

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