After a three-year hiatus, El Nino has made a comeback and is expected to bring about significant weather anomalies later this year. The El Nino phenomenon, characterized by warm ocean temperatures in the Eastern Pacific near South America, has the potential to trigger tropical cyclones heading toward vulnerable Pacific islands, heavy rainfall in South America, and drought conditions in Australia.
The U.S. National Oceanic and Atmospheric Administration's Climate Prediction Center recently issued an advisory confirming the return of El Nino. The climate pattern had been preceded by a three-year period of La Nina, which typically leads to a slight decrease in global temperatures. However, the reemergence of El Nino indicates the onset of hotter conditions.
According to the advisory, weak El Nino conditions became apparent in May as sea surface temperatures across the equatorial Pacific Ocean rose above average. The combination of warm waters and a possible slowdown or reversal of easterly trade winds contributes to the formation of El Nino.
The previous occurrence of El Nino in 2016 coincided with the hottest year on record. With the additional influence of climate change, 2023 or 2024 could potentially experience new temperature highs. Confirmation of El Nino typically relies on assessments from two major agencies: the U.S. National Oceanic and Atmospheric Administration (NOAA) and Australia's Bureau of Meteorology (BOM). Both agencies employ different criteria, with the Australian definition being slightly more stringent.
NOAA declares an El Nino when ocean temperatures in the eastern and central equatorial Pacific are 0.5 degrees Celsius (0.9 degrees Fahrenheit) above normal for the preceding month, persisting or expected to continue for five consecutive three-month periods. The agency also takes into account a weakening of the trade winds and cloud cover. Australia's BOM requires a higher temperature threshold, considering key regions in the eastern Pacific to be 0.8 degrees Celsius (1.5 degrees Fahrenheit) warmer than average.
Australia recently issued its own bulletin indicating a 70% chance of El Nino developing this year. NOAA projects a 56% probability that this El Nino, expected to peak in strength during the Northern Hemisphere winter, will be a strong event. In this case, Eastern Pacific sea surface temperatures would be at least 1.5 degrees Celsius higher than normal, potentially resulting in more severe impacts, such as drought and cyclones, worldwide.
It is worth noting that El Ninos come in two variations. Eastern Pacific events, like the powerful 1997-98 El Nino, have their warmest waters near the west coast of South America. On the other hand, Central Pacific El Ninos occur near the equator around Hawaii, as was the case in the most recent 2015-16 event. Depending on the location of warm waters, weather anomalies can vary, leading to drier or wetter conditions in specific regions.
The agricultural sector is already feeling the effects of the El Nino phenomenon. Early indications of hot and dry weather associated with El Nino are posing a threat to food producers across Asia. Conversely, American growers are hoping for heavier summer rainfall to alleviate the impact of severe drought.
In Australia, the El Nino could cause winter crop production to decline by 34% from the record highs seen previously. Additionally, palm oil and rice production in Indonesia, Malaysia, and Thailand, which collectively supply 80% of the world's palm oil, may be affected. In India, where summer crop growth heavily relies on monsoon rains, the impact of El Nino could potentially be offset by the Indian Ocean Dipole, also known as the Indian Nino. However, below-average rainfall is anticipated for northwestern parts of the country.
