Which volcanic eruption in 1991 caused a measurable short-term drop in global temperatures?

The 1991 eruption of Mount Pinatubo caused a measurable short-term drop in global temperatures by injecting sulfur dioxide into the stratosphere.

The eruption occurred in the Philippines on 15 June 1991 and was one of the largest volcanic eruptions of the 20th century. Its ash and gases rose high into the atmosphere, where sulfur dioxide formed sulfate aerosols that reflected some incoming sunlight back to space.

Global average surface temperatures fell by about 0.5 °C during the following year or two. This cooling was temporary because the aerosols gradually settled or were removed from the atmosphere. The eruption did not permanently reverse long-term human-caused warming.

Mount St. Helens, which erupted in 1980, was highly destructive locally but released much less sulfur dioxide. Krakatoa’s 1883 eruption also produced global effects, but it was not the 1991 event associated with this specific modern temperature estimate.