Peak Re’s head of analytics lays out the problem


Currently the Pacific is in an El Niño Southern Oscillation (ENSO) neutral state, but over the first half of the year, equatorial Pacific sea surface temperature anomalies indicated that an El Niño event will occur this year, writes Peak Re head of analytics Graham Cook.

According to the Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA), El Niño has a 70% chance of happening in the Northern summer and an 80% chance in the Northern fall/winter, with the event being of weak to moderate strength. 

More recently, the Australian Bureau of Meteorology downgraded the chance of an El Niño to 50%, as the atmosphere above has largely failed to respond and subsequently there is some cooling taking place in the central and eastern tropical Pacific.  Nevertheless, the warmer than average waters suggest a likely El Niño, albeit weak.

An El Niño is the warm phase of El Niño Southern Oscillation and is characterised by an anomalous warming of the eastern and central tropical Pacific and has consequences for weather globally.

El Niño events have lasted for as short as 7 months and as long as 19 months.  Since 1950 the average length of an El Niño is 11.8 months and usually starts in May or June and ends in the following April. The strongest El Niño since 1950 occurred in 1997-1998, with the last strong one occurring in 2009-2010.  

El Niño effects on precipitation are strongest in South-East Asia and the western Pacific, mainly in the dry season between August and November.

One main concern of an El Niño is that agriculture is more prone to droughts than floods.  El Niño is correlated with large scale below-average rainfall over southern and eastern inland areas of Australia and above day-time temperatures over southern Australia. This increases wildfire severity and frequency; reduces wheat exports and affects other exports and prices of commodities. 

During a typical El Niño the Asian monsoon generally weakens and moves closer to the equator, leading to summer droughts in regions of China, India, Pakistan, Bangladesh, Sri Lanka, Nepal, Myanmar, and Afghanistan, and heavy rainfall in some areas.  Data from 1868 onwards from NOAA and the India Meteorological Department shows there is a significant correlation between droughts and El Niño.  For five main crops in India, including wheat and rice, it was found that four of the five crops experienced a reduction in yield during El Niño years, with rice experiencing the largest decline and wheat unaffected.  Also, the palm oil industry has reduced yields and increased prices due to below average rainfall in Indonesia and Malaysia.

As El Niño is a strong interplay between the ocean and the atmosphere in the Pacific basin, the modulation of tropical cyclones due to El Niño is expected.  Research reports have shown that the North-west Pacific basin as a whole has more tropical cyclones in an El Niño year than a La Niña year. During El Niño events there is often a south east translation of the mean tropical cyclone genesis area, as well as a southerly flow that develops over the East China Sea and the Sea of Japan that is more likely to steer storms north, therefore tending to miss the Philippines. 

It has been posited that storms are more intense due to this translation of storm genesis in El Niño years as they are over warm waters longer.

The El Niño cycle is associated with increased risks of vector-borne diseases such as malaria and dengue fever.  In dry climates, heavy rainfall can lead to puddles that provide a breeding ground for mosquitoes and in hot humid climates a drought can turn a river into pools that again are good breeding grounds for mosquitoes.

A recent study from Cambridge University looked at the macro-economics of El Niño on 33 countries, 11 in APAC, found that there were definite shocks to GDP growth and inflation.  The results of the analyses indicated that Australia, Indonesia, India, Japan, and New Zealand had a short term fall in economic activity, whereas China actually benefited from El Niño and most countries experience a short term inflationary pressure following an El Niño.

Previously, there was no strong consensus on how climate change will affect El Niño, as climate models have produced conflicting results. A recent study published in Nature Climate Change concluded that with the current rate of carbon emissions there would be twice as many extreme El Niños over the next 100 years. 

If correct, this could affect the property, health and agriculture sectors adversely leading to more damage, more deaths from disease and more poverty due to crop failures.