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05 Jun 2014

A return of El Niño?

Wai Shin

by Wai-Shin Chan

Climate Change Strategist, HSBC

A return of El Niño?

El Niño conditions occur when warm water moves from the western equatorial Pacific to the eastern side

The chance of El Niño – the warming influence that originates in the Pacific Ocean – developing in 2014 has increased to 65 per cent, according to the National Oceanic and Atmospheric Administration. This natural phenomenon can change rainfall patterns and weather causing devastating droughts, storms, forest fires or floods in many countries.

Essentially, the American western coast experiences more rain while the western Pacific can suffer drought. So while El Niño can hurt crop yields in Australia and fish stocks in South America, it might also bring welcome rainfall to drought-stricken California.

El Niño conditions occur when warm water moves from the western equatorial Pacific, around Indonesia, to the eastern side, around Peru, and prevailing trade winds change. It occurs every two to seven years and can last from nine months to a few years.

This natural phenomenon can change rainfall patterns and weather causing devastating droughts, storms, forest fires or floods in many countries

The seasonal effects have been strongest between September and November and weather changes can affect not only agriculture but industries such as construction and retail. The last major El Niño, in 1997-98, led to around 23,000 deaths and USD35 billion to USD45 billion of losses globally – but there can be gains, such as higher crop yields, and the US as a whole was estimated to have benefited by a net USD15 billion from reduced heating costs and increased seasonal sales.

However, reduced rain in many parts of equatorial Asia and eastern Australia can have devastating effects on agriculture. Lack of rainfall can exacerbate Indonesia’s forest fires with the smog engulfing Singapore while flooding along the eastern Pacific coast can cause significant infrastructure damage.

Warmer shallow seas around Peru and Ecuador can drive fish towards cooler, more nutrient-rich water, reducing fishing catches. There tend to be fewer Atlantic hurricanes during El Niño episodes, meaning less disruption to offshore oil production, but more Pacific hurricanes.

The complexities of the global climate system mean many knock-on effects have not yet been adequately studied. For example, some animal species don’t adapt well to sudden temperature changes while others, such as insects, migrate to seek better temperatures and can spread diseases.

Climate change does not cause El Niño, but it may exacerbate its effects as more heat energy is introduced to the system through global warming. Since the effect on the weather can be so significant, the long-term average climate is also affected.

Historical temperature records have been set during El Niño episodes and some scientists believe an El Niño in 2014 could trigger more records and hence a continuation of the global warming trend. It is difficult to attribute singular events to climate change, but an increase in the overall frequency is likely to be a tell-tale sign of the effects of climate change.

This research was first published on 22 May 2014.
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