La Niña Likely to Return with High Global Temperatures

Current Situation/La Niña Forecast:

After a record-setting year for global temperatures, we are approaching the end of a strong El Niño and are likely heading back into La Niña with continuing extremely high global temperatures. El Niño provided much-needed relief for some by improved precipitation after enduring three years of La Niña while it brought heartache to others, particularly in parts of northern South America, Central America, Southern Africa, Southeast Asia, and the northern Maritime Continent due to reduced precipitation.

The El Niño-Southern Oscillation (ENSO) remains in the weakening El Niño phase. The National Oceanic and Atmospheric Administration Climate Prediction Center (NOAA CPC) is forecasting a return to ENSO-neutral (neither El Niño nor La Niña) during the April-June period (Figure 1). The Australian Bureau of Meteorology (BoM) has already stated a return to ENSO-neutral conditions. However, NOAA has already issued a La Niña Watch. According to NOAA CPC forecasts, La Niña could develop as soon as June to August, with a 60 percent chance. After that, the chances of developing continue to rise with an 80 percent chance or greater beginning during the August to October period. While forecasts made during this time of the year tend to be less accurate than those later in the season, several signs suggest that La Niña is coming.

Figure 1: The official April 2024 NOAA CPC ENSO probability forecast, based on a consensus of CPC and IRI forecasters. Source: International Research Institute

Precipitation Changes Coupled with High Temperatures:

Should La Niña materialize, drier-than-average precipitation is likely in East Africa, Central and South Asia, southern South America, the southern United States, northern Mexico, and eastern East Asia. Conversely, parts of Southeast Asia, Australia, Southern Africa, Central America, and northern South America might experience above-average precipitation.

Extreme high temperatures will also likely be a factor, particularly for those regions at risk of experiencing drier-than-average conditions given heat extremes can worsen drought stress. Last year was the warmest on record since global records began due to the influences of the strong El Niño and climate change. While La Niña events typically bring cooler global temperatures, it is unlikely to significantly change in 2024. This year is already breaking records, with January, February, and March all becoming the warmest respective months on record. The outlook for the rest of the year looks much the same, with a very high chance that 2024 will rank in the top five of warmest years on record.

Potential Crop Impacts:

La Niña events have historically led to slightly lower than average global-level yields for soybeans (up to 2 percent) and slightly higher than average global-level yields for rice (up to 2 percent), while not significantly impacting global-level yields of wheat or maize. How the current potential La Niña event will impact agricultural production is uncertain as no two events are the same. With global temperatures at unseen levels, the negative effects could potentially be exasperated. However, based on historical La Niña events, some crops in some regions will likely experience yield impacts. For wheat, yields tend to be positively impacted in Argentina, southern Brazil, Morocco, Portugal, Australia, China, and India, while negatively impacted in parts of the United States, East Africa, and Central Asia. For maize, yields tend to be positively impacted in parts of Southeastern Africa, China, India, and Thailand, while negatively impacted in Argentina, Paraguay, Bolivia, and the US. For rice, yields tend to be slightly positively impacted in China, India, Pakistan, Central Asia, Cambodia, Vietnam, Thailand, southern Brazil, and Central America, while negatively impacted in the Middle East, Bolivia, and the US. For soybeans, yields tend to be positively impacted in Brazil, Southern Africa, India, and China, while negatively impacted in Argentina, Uruguay, and the US. The negative impacts tend to be lessened for irrigated crops than rainfed crops. However, only when the likely La Niña event arrives in combination with likely extremely high global temperatures will its actual impacts on agriculture begin to be known.

Figure 2: Historical crop yield conditions during La Niña events for wheat, maize, rice, soybeans, and sorghum using FAO country-level yield data and ERSSTv5 from 1961-2020. In countries with more than one crop affected, the colour reflects the strongest effect. Note: FAO data is national and annual resolution, which masks expected relationships in areas with multiple crops (e.g. the Horn of Africa).