The results show that El Niño events are likely to improve the global mean soybean yield by 2.1 to 5.4%, but the effect on maize, rice and wheat is more variable, with changes in yield ranging from a 4.3 reduction to a small increase of 0.8%.
Meanwhile, overall global-mean yields of all four crops during La Nina-affected years tend to be below normal (−4.5 to 0.0%).
The climatic phenomena trigger changes in temperature and rainfall. Episodes are caused by changes in the sea surface temperature in the eastern tropical Pacific Ocean.
"This new work tells us that we can predict when the bad years will be, ahead of the harvest," explain co-author Prof Andy Challinor from the University of Leeds, UK.
Researchers found that the high reliability of ENSO forecasts (see panel) presented an opportunity to link it with global crop yields data. This, in turn, would be potentially beneficial for food monitoring and famine early warning systems.
The scientists suggested that the forecasts could help mitigate impacts by influencing planting dates, crop choices, as well as considering other inputs such as chemical treatments and irrigation.
"An improved response to ENSO could reduce the risk of malnutrition; allow for an increase in agricultural investment in positively impacted years; and improve the adaptation capability to climate variability and change."
Know your El Niños and La Ninas
The periodic warming (El Nino) and cooling (La Nina) of sea surface temperature in the eastern Pacific Ocean are phases in the naturally occurring phenomenon El Nino-Southern Oscillation.
El Nino and La Nina cause shift in the position of the jetstream, which - in turns - alters temperature and rainfall patterns in many regions around the world.
These changes result in extreme weather conditions, such as drought or abnormal rainfall, in the affected areas. This has a knock-on effect on crop yields, which are heavily influenced by temperature and precipitation levels.
What about this year?
Earlier this year, the UN World Meteorological Organization predicted a warming of the tropical Pacific, with a majority of models indicating that an "El Nino may develop around the middle of the year".
This week, data collected by Nasa satellites showed that conditions in the eastern Pacific at the beginning of May 2014 were similar to those experienced in May 1997 - a year that saw one of the powerful El Nino episodes in the 20th Century, which claimed an estimated 2,100 lives and caused US $33bn damage to properties.