26 May 2015

A stronger El Nino: what does this mean for global weather?

After failing to materialise last year, despite predictions from experts around the world, El Nino finally officially arrived back in March, according to NOAA’s Climate Prediction Center.

Its arrival was more than six months after originally expected and much weaker in strength than initially anticipated.

However, the latest predictions from climate models suggest that this likely to change in the coming months, with a moderate to strong El Nino on the cards.


What is El Nino and why is it important?

El Nino is a naturally occurring ocean-atmosphere phenomenon that is characterised by unusually warm surface water temperatures in the central and eastern Pacific.

It is important because it has a significant impact on the climate in many parts of the world.

The most notable effect that El Nino has on the climate is a warming influence on global average temperatures – something that was observed during a strong El Nino in 1998.


El Nino’s influence on temperature

However, it should be noted that no two El Nino events are ever the same and its effects will work with other drivers that influence the world’s climate system.

Nevertheless, historical data shows that the effects of El Nino can be felt far and wide – much like dropping a pebble in a pond and the ripples extending outwards.

Adding heat energy to the atmosphere

The impacts of El Nino can extend far and wide, but tend to have greatest influence in places that sit within the tropics.

This is because in these parts of the world, the weather is heavily influenced by the amount of heat present in the atmosphere and oceans.

Heat is a fuel for the weather on our planet and if you add more to the global system, it can influence temperature and rainfall patterns – potentially making weather more extreme.


El Nino’s influence on precipitation

Where in the world is likely to be affected?

The anomalously warm ocean waters in the Pacific Ocean are expected to increase the number of hurricanes and typhoons in the regions, as well as making them more intense.

In the Atlantic Ocean, the effect tends to be the opposite, with fewer hurricanes – something that both the Met Office and Colorado State University expect to be the case this season.

Further afield, El Nino’s influence may reach as far as India. The India Meteorological Department’s long range forecast for the annual southwest Monsoon suggests that rainfall is likely to be below average this year.

The annual monsoon rains are vital to India’s agriculture, as well as giving relief to the intense heatwave that precedes it – often killing hundreds. If agriculture is hit, there could be a knock-on effect on global food prices.

Closer to home, the influence of El Nino on the UK’s weather is somewhat tenuous, although there are hints that it can give us colder than normal winters – something that happened back in the winter of 2009/10.

Graphics: NOAA, Met Office

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