Web alert: 70% chance of an El Niño event
07 May 2014
Australia Bureau of Meteorology has announced a 70% chance of an El Niño event occurring as early as July 2014 potentially bringing drought across the Asia-Pacific region and heavier-than-usual rains to South America.
El Niño events, which are caused by the periodic warming of the Pacific, occur every two to seven years and are associated with warmer-than-average years. The last El Nino was from 2009 to 2010, and since then the Pacific has either been in its cooler state, called La Nina, or neutral.
To qualify for El Niño status, four conditions need to be met that assess sea temperatures, winds, climate models and the Southern Oscillation Index (SOI). The SOI gives an indication of the development and intensity of an El Nino or a La Nina, and it is calculated using the pressure differences between Tahiti and Darwin.
Weather-altering patterns have been observed in recent months with the steady warming of the tropical Pacific Ocean causing large warm anomalies in the ocean sub-surface (up to +6 °C) and increasingly warm sea surface temperatures. The other atmospheric characteristics of El Niño are persistent weakening of the trade winds and a consistent increase in cloudiness near the Date Line, which will become evident over the coming months.
El Niño impacts climate across much of the world, causing below average rainfall in the western Pacific and Indonesian regions, and increased rainfall in the central and eastern Pacific. El Niño events can therefore ruin agricultural markets worldwide as farmers contend with drought or too much rain, leading to high commodity prices from coffee, sugar, cocoa, wheat, rice through to palm oil.
Forecasters from the U.S. and the United Nations have agreed an event may happen this year.