In an article published in the scientific journal, "Nature", scientists at the Federal Institute of Technology in Zurich say they have found evidence that El Niño also affects Europe - a subject which has been controversial in the past. The research team, headed by climatology professor Stefan Brönnimann, looked at the years 1940 to 1942 in particular. "The three winters were unique. Two of them were the coldest in the last century," said Brönnimann.
In Switzerland, temperatures hit a record low at the Jungfraujoch mountain in the Bernese Oberland, while the thickest ozone layer of the last century was measured above Arosa. This coincided with a particularly strong and long-lasting El Niño which affected the weather in South America and Asia. To find out if there were any connections, the researchers gathered metrological data from this time for Europe, the Soviet Union and North America. The data showed that the North Pacific Ocean and Europe were very cold, but there were higher temperatures in Alaska, including the warmest for the whole 20th century in 1941-1942. The ozone layer was also at its thickest over the Artic and Europe.Comparing these results to other meteorological data, the climatologists discovered a pattern. The strongest results came from 1969-1970, 1997 and 1998 — all known El Niño years. "The cause of all these phenomena is El Niño," said Brönnimann. One of the most important factors in causing an El Niño is the prevailing trade winds that blow from east to west across the equatorial pacific. They take the ocean's warm surface water towards Southeast Asia, where clouds form and fall as the Monsoon rains. In strong El Niño events, the trades slow down or reverse their direction and the rains fall in South America, while Southeast Asia suffers drought.