What is El Nino?
21st May, 2015
For more than a year now, weather forecasters around the world have been predicting that a phenomenon known as El Niño may be close. This is a process that occurs every few years in the tropical Pacific Ocean and can result in powerful fluctuations in our climate system. Over the past week or so, experts have declared that this phenomenon has now begun.
“The likelihood of El Niño is high but its eventual strength in the winter when it has its major impacts worldwide is still unknown…we will know in the summer how strong it is going to be.” - Professor Eric Guilyardi of the Department of Meteorology at the University of Reading
In the past El Niño has been known to cause:
- Poor monsoons in Southeast Asia
- Droughts in Southern Australia, the Philippines and Ecuador
- Blizzards in the United States
- Heatwaves in Brazil
- Extreme flooding in Mexico
How Does El Niño Differ?
The usual situation in the Pacific Ocean is that winds blow from the eastern side of South America in the direction of Australasia and Asia. As they do they carry warm water near the surface in the direction of the wind. This causes warmer waters to build up around the western side of the Pacific, with waters in the east replaced by cooler water in a process known as upwelling. As a result we commonly see a temperature difference across the Pacific, with higher temperatures in the west and cooler temperatures in the east.
During El Niño this changes, with these winds either weakened or reversed. This causes less of the warmer water to travel in the direction of Asia and reduces the amount of cold water upwelling in the east. As a result this causes the usually colder areas of the ocean to warm and cancel out the usual temperature difference. With the areas of warm water shifted, weather patterns around the equatorial Pacific can vary considerably from the norm.
Will El Niño Impact Us Here In The UK?
Whilst this is a phenomenon that occurs on the other side of the world, there is always speculation in the media about how El Niño may impact our weather closer to home. The truth is that during spring and summer even the strongest El Niño will only slightly impact upon our weather and it is unlikely to be a major influence on our weather over the next few months.
As we look further ahead to the winter months, our weather is driven by a number of factors. At this moment in time, the Met Office considers the chances of El Niño increasing the risk of an extremely cold winter to be small.
You can find out more about how the El Niño phenomenon impacts upon weather systems by watching the video below from the Met Office.