Figure 2 Comparison of modeled (black line) and observed (blue) impact of a major volcanic eruption on the temperature of the lower atmosphere. The eruption of Mt. Pinatubo in the Philippines, during June 1991, injected vast amounts of sulfur dioxide directly into the stratosphere. The gas quickly transformed into sulfuric acid particles that enshrouded the Earth and blocked part of the incoming solar radiation. The apparent effect is a drop of about 0.6°C in the globally-averaged temperature, lasting about two years. From J. Hansen et al., in National Geographic Research and Exploration, vol 9, no 2, pp 142-158, 1993.