Critics of global warming often argue that the earth’s temperature has not increased every year. But cooler periods of time may be explained by taking into account the effect of volcanic eruptions, such as the one weâ€™re listening to right now. Iâ€™m Jim Metzner and this is the Pulse of the Planet.
ambience: Volcanic Eruption
Powerful volcanic eruptions can put enough particles into the atmosphere to filter out sunlight and help cool the earth. According to Alan Robock, an associate professor of meteorology at the University of Maryland, the net result of these eruptions would be to mask the effects of global warming.
â€œFrom the beginning of this century, up until about 1940, the climate warmed quite a bit. What probably happened was, this was an unusual period that was particularly free of volcanic dust. There were no large volcanic eruptions for that whole period, so the atmosphere was warming up in response to being clean, when before it had a lot of dust in it.â€
â€œSince the 1940â€™s, the climate stayed relatively constant, and this was a time when there were more volcanic eruptions which were counteracting the warming effect of the greenhouse gases. So volcanoes, which cause cooling, combine with greenhouse gases, which caused warming, (and) had a cancelling-out effect.â€
Several years in the last decade were among the warmest recorded in a century, but after Mexicoâ€™s El Chichon volcano erupted in 1982, global temperatures cooled for a few years.
â€œI think the temperature of the planet today would be warmer if there hadnâ€™t been the El Chichon eruption of 1982, and hadn’t been other volcanic eruptions. I think the climate change of the last 100 years would probably have been a gradual smooth warming rather than the irregular path that it’s taken.â€
According to Professor Robock,as more and more greenhouse gases accumulate in our atmosphere, global warming will ultimately override the cooling effects of volcanic eruptions.
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