Professor Min Seung-ki  and Dr. Paik Seung-mok of Division of Environmental Science and Engineering of POSTECH and researchers of the French National Centre for Scientific Research, Swiss Federal Institute of Technology in Zurich, and University of Edinburgh discovered that El Niño produced by volcanic eruptions plays a key role in the decrease in global precipitation. Such finding was published in Science Advances, a sister journal of Science.
After volcanic eruptions, an immense amount of sulfur dioxide dust is emitted, and the global average temperature decreases due to such dust reflecting sunlight and, therefore, blocking solar heat from reaching the Earth’s surface. Along with such cooling effect, volcanic activities reduce the global terrestrial precipitation, but the size of reduction was inaccurate since it varied among climate model simulations. For the first time, the joint research team confirmed that the main factor for the reduction in precipitation after volcanic eruptions is the difference in El Niño’s reaction.
El Niño is a climate change that occurs every three to eight years due to weakened trade winds in the equatorial Pacific Ocean and the increase in sea surface temperatures in the eastern Pacific. It causes extreme weather conditions, such as droughts and downpours, across the globe. Precipitation decreases occur especially in the global monsoon region, including Southeast Asia, India, South Africa, Australia, and Latin America.
Until now, there were researches claiming that volcanic eruptions reduced global precipitation, but the specific mechanism behind was not known for certain. However, comparing several climate model simulations, the research team found that El Niño appeared in the year following a volcanic eruption in most models and precipitation reduced significantly around the global monsoon region. Furthermore, as the strength of El Niño increased, the decrease in precipitation was more pronounce. The team also discovered that as the volcanic forcing and warm water volume in the western Pacific increased, a stronger El Niño developed, and this in turn intensified the decrease in precipitation. 
These findings are expected to be used to identify side effects of geoengineering techniques and for climate prediction of later years.