Mount Pinatubo, a dormant volcano in the Philippines, erupted without warning in the summer of 1991. These satellite photos show the event in dramatic detail. Included in the debris thrown out was about 20 million tons of sulphur dioxide which, converted into sulphuric acid particles in the atmosphere is now blocking out some of the sun's radiation. this may cause the world to cool by about 0.5 degrees centigrade over the next few years (and may temporarily offset global warming). The presence of the sulphuric acid droplets, however, has also caused an acceleration of the depletion of ozone levels in the atmosphere.