Mild to moderate El Niño conditions in 2009/10

El Niño phenomenon

El Niño is a large-scale substantial warming of surface waters in the central and eastern Equatorial Pacific Ocean, coupled with changes in the atmosphere that affect weather patterns across much of the Pacific Ocean. These changes include: i) a negative value of the Southern Oscillation Index (SOI), ii) the sustained weakening of Trade winds and iii) increased cloudiness over the tropical Pacific. El Niño is the oceanic component, while the Southern Oscillation is the atmospheric one. This combination gives rise to the term ENSO (El Niño Southern Oscillation). El Niño is an irregular event appearing every 2 to 7 years, with different intensity and duration and usually peaks around Christmas, hence the name of the phenomenon: El Niño (Spanish for Christ Child). Maximum strength is usually maintained until February. Important changes in temperatures and precipitation patterns are often noticed during El Niño, having a positive or negative impact on agriculture.

The overall changes in the ocean surface temperatures caused by El Niño also affect marine fisheries, particularly in the eastern Pacific. However, the particular character of the impact differs quite markedly from one event to another, even with similar changes and patterns in the Pacific Ocean. Therefore, no precise quantitative association between the occurrence of El Niño and changes in agricultural production has been established and it is difficult to forecast the impact of El Niño. The impact on agriculture will decisively depend on the relative timing of the El Niño and the crop calendar in a particular region. La Niña refers to the "cold" equivalent of El Niño.

The oldest El Niño recorded dates back to 1578, when torrential rains and floods devastated crops in northern Peru. During the past forty years, ten of these major El Niño events have been verified. El Niño event in 1982/83 resulted in severe flooding and drought in several parts of the world, as well as the decline of a number of fish stocks, and reportedly caused over US$10 billion in weather-related damages. In 1991/92 El Niño resulted in a severe drought in Southern Africa. The last strong El Niño occurred 12 years ago in 1997/98, with drought and floods in several areas of South America and South-East Asia that had severe adverse effects on agricultural production and infrastructure.

El Niño event in 2009/10

This year, since early June, indicators consistent with the development phase of an El Niño phenomenon have been observed. Forecasts by the end of October and overall conditions in the equatorial Pacific indicate a high probability for maintaining weak to moderate El Niño conditions through the end of the year, and to continue until early 2010. Although a strong El Niño phenomenon is not forecast at this stage, and the associated climatic effects in most regions are expected to be weak, these may be, nonetheless, significant at local level (for details see: http://www.fao.org/nr/climpag/cl_ind_3_en.asp).

Possible regional effects on agriculture

In Southern Africa, the occurrence of a weak to moderate strength El Niño weather pattern could increase the probability of below normal precipitation during the 2009/10 rainy season (October-March). However, satellite-based rainfall estimates indicate good and well distributed rains in most parts of Southern Africa during October. This has led to favourable ground conditions for planting of the 2009/2010 main cereal crops, particularly in the "maize triangle" of South Africa, which is the major producer in the sub-region. The situation needs to be closely monitored in the coming months as the season has just started.

By contrast in Eastern African countries, El Niño conditions are expected to produce above-normal rains in October-March, which are generally favourable for the secondary 2009/10 crop seasons planted in October-November and harvested in February-March. However, these rains may hamper harvesting of the main season cereal crops from October-November. El Niño phenomenon could also result in exceptionally heavy rains and floods in the sub-region negatively affecting food production and livestock conditions as in the strong event of 1997/98. So far, current information indicate above normal, heavy rains in October this year in eastern parts of the sub-region, comprising Ethiopia, Somalia, Djibouti and Kenya. These rains have eased drought conditions in pastoral areas and benefit planting of the secondary crops.

In Asia, El Niño conditions are associated with below-average precipitation from October to March in parts of India, Bangladesh, and Myanmar, parts of China and Sri Lanka and heavy rains in parts of Afghanistan, Pakistan and Nepal. As most of the main season rice crops are harvested from October-November, no major effect is expected in the 2009 rice productions which in aggregate are forecast at around record levels. However, in India, a reduced main season rice crop is forecast due to poor monsoon season during summer months, which some analyst associated also with El Niño. Possible dry weather in coming months could negatively affect the secondary cropping seasons, mainly rice. By contrast, in Pakistan, Afghanistan and Nepal abundant precipitation could benefit the winter seasons wheat and rice crops.

In Latin America and the Caribbean, the impacts of El Niño may be significant at regional level. In Central America, El Niño usuallyleads to below normal precipitation in parts and fewer or less intense hurricanes during the Atlantic hurricane season. In September and October a rainfall deficit was recorded across the region negatively affecting planting of the 2009 secondary "de postrera" cereal and beans season in some parts of Nicaragua, Guatemala, Honduras and El Salvador. However, heavy precipitation in early November, associated with the passage of Hurricane IDA, has resulted in severe damage to infrastructure and agriculture. While the drought situation has been reversed, rains were too late to avoid reductions in the area planted.

In South America, El Niño phenomenon is forecast to result in below normal precipitation in northern parts of the region. In Venezuela dry weather in past months has affected the 2009 maize crop in the main producing areas and the output is forecast to be reduced. No other significant weather anomalies have been reported in the north of the region. By contrast, in southern parts, including the major cereal growing areas of Argentina, southern Brazil and Uruguay, above normal rains are forecast in the period October-March. In Argentina heavy rains in October associated with El Niño, have delayed the start of of the 2009/10 maize crop planting. However, they benefited somewhat the 2009 wheat crop in central-eastern farming areas that had been negatively affected by extremely dry weather since May. Overall, the impact of El Niño in the southern countries of the region is expected to be stronger towards the end of the year, when harvesting of the wheat crops and planting of the 2009/10 coarse grain crop will be well advanced. Should forecasts of above-normal rains in the sub-region materialize reductions in coarse grains area planted and wheat quality may occur.

FAO will keep closely monitoring weather anomalies in the coming months and assessing possible effects these may have on agricultural production and food security in various parts of the world in order to provide early warnings and to enable mitigating actions.