Volcano Journal Entry
Volcanoes Help Bring On El Niño (December 5, 2003)
Space radar view of Mount Pinatubo in Philippines. Lava from its eruption appears as fingers of dark red surrounding the central crater. The volcano's eruption in 1991 has been linked to El Niño. Courtesy NASA/JPL.
New research links some large volcanic eruptions with El Niño. Researchers say a major eruption in the tropics doubles the chance that El Niño will occur the following winter.
El Niño is a periodic global weather pattern marked by warmer ocean water in the Pacific Ocean along the equator. As the water warms, the prevailing east-west trade winds die down. These ocean current and atmospheric changes have been linked to extremes in weather conditions around the globe, including floods and droughts.
The researchers looked for clues in polar ice cores, tree rings, and coral reefs to track periods when Earth's climate suddenly changed. They compared this data to the dates of major volcanic eruptions since 1649. They discovered a clear connection between volcanoes that erupted in the tropics and sudden climate changes.
After a volcanic eruption, huge amounts of ash hang in the atmosphere. The ash forms a blanket that blocks sunlight and cools the atmosphere by about one-half degree Fahrenheit. As a result of interactions between the atmosphere, oceans, and land, convection currents carry warm water to the equator in the Pacific Ocean. This in turn kicks off a new El Niño cycle.
One of the best examples of this effect was the Mount Pinatubo eruption in the Philippines in 1991. The eruption was likely a major factor in the El Niño pattern seen the following year.
