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IN 1815, the Indonesian volcano Tambora eruption, measured 7 on the Volcanic Explosivity Index (VEI). It emitted ash and volcanic gases into the atmosphere more than any other eruption in history (about 10 times bigger than the Mt. Pinatubo eruption) and impacted climate worldwide throughout 1816. The year 1816 was known as “the year without summer.” The northeasterly region of the US and Europe were particularly hard hit, with snowfalls as late as August and massive crop failures.
In 1883, the Indonesian volcano Krakatau’s explosions hurled an estimated 45 cubic km of debris darkening skies up to 442 km from the volcano. The eruption was rated as VEI of 6. In the immediate vicinity, the dawn did not return for three days. The four years following the explosion were unusually cold winter-like conditions, and the winter of 1887-1888 included powerful blizzards. Record snowfalls were recorded worldwide.
The 1912 eruption of Novarupta in Alaska, the most powerful volcanic eruption of the 20th Century, did not cause global cooling. Climate-cooling aerosols stayed north of 30°N latitude.
A whole series of large eruptions continue from Mt. St. Helens in 1980, El Chichón in 1982, and finally the 20th century’s second-largest eruption on Earth, most destructive, and deadliest eruption, Mt. Pinatubo in 1991.
The Pinatubo eruption cloud reached over 40km into the atmosphere and ejected about 17 million tons of Sulfur dioxide, just over two times that of El Chichon.
The sulfur-rich aerosols circled the globe within three weeks and produced a global cooling effect approximately twice that of El Chichon. The Northern Hemisphere cooled by up 0.6 degrees C during 1992 and 1993. The aerosol particles may have contributed also to an accelerated rate of ozone depletion. Some scientists argue that without the cooling effect of major volcanic eruptions, global warming effects caused by human activities would have been far more substantial. (Floro Mercene)