Is an El Niño on the way and what might its impacts be?
July 2014 - This year has seen changes taking place in the equatorial Pacific Ocean that have heralded the onset of an El Niño event, with the potential to cause major climatic impacts around the world.
This is an update to the report published in June 2014.
A new report considers the current evidence for an El Niño event this year, discusses the potential strength of the event, and considers what its global impacts might be.
The current assessment presented in this report is that an El Niño is probable, but that its strength is likely to be weak to moderate, similar to the 2009/10 event. The feedbacks between the atmosphere and ocean that act to amplify a developing El Niño were not active in the Pacific basin in late June, raising questions about its evolution over the coming months and its impacts on the global climate system.
This report also looks in more detail at the different flavours of El Niño and their global impacts, with the aim of providing more discriminatory evidence on possible impacts of this year's developing El Niño. In particular the report emphasises that the differing types of El Niño affect global mean surface temperatures differently, with only strong East Pacific El Niño events leading to a large global warming.
The current assessment is that the warmth of the equatorial Pacific will continue and that an El Niño of weak to moderate strength seems more probable than a strong event; the likelihood of the sea surface temperature anomalies exceeding 2 °C is very low.
Potentially, the biggest impact of the current El Niño in the coming three months is on the Indian monsoon rains. The latest predictions from the Met Office indicate that the risk of a poor monsoon is two to three times greater this year than normal. So far the progress of the Indian monsoon rains bears this out, with a late and weak start to the season with less than 50% of normal rainfall by mid-July over some parts of India, and an overall current deficit of 25%.
Other possible impacts include:
- slightly weaker than average cyclone activity in the Atlantic;
- more active East Pacific cyclone activity associated with the warmer ocean along the Peruvian coast;
- greater typhoon activity associated with above average ocean temperatures in the tropical North West Pacific;this has already commenced with three major storms (Neoguri, Rammasun and Matmo) in July;
- slightly increased likelihood of wetter than normal conditions over southern China;
- continuation of drought conditions in the western USA with associated risks of forest fires;
- moderate increase in global mean temperatures, particularly in 2015.