Explainer — El Niño’s impact and what to expect from La Niña
The El Niño weather pattern has faded and its polar opposite, La Niña, is widely expected to re-emerge soon as the surface temperatures in the eastern Pacific cool. Here are a few points about these phenomena, the consequences of the latest El Niño and the anticipated effects of La Niña.
The turning tide of the ENSO cycle
El Niño and La Niña form part of what is known as the El Niño-Southern Oscillation (ENSO) cycle – a meteorological mouthful.
This cycle is natural and linked to westward trade winds along the Pacific in equatorial latitudes. When they weaken, warm water flows to the east, giving rise to El Niño (Little Boy in Spanish). South American fishermen first noticed this pattern in the 17th century and since it typically peaks in December, the reference is to the Christ child.
La Niña (Little Girl) is triggered when trade winds are stronger than usual and channel warm water towards Asia. In the eastern Pacific, this causes cold water to “upswell” to the surface.
These events usually last nine to 12 months but can linger for years. Both patterns typically have impacts which vary from region to region and include drought, deluge and more intense hurricanes.
In between this little lad and lassie the ENSO is in a neutral phase, which is the current stage of the cycle. El Niño recently faded and La Niña is seen forming by the Austral spring, perhaps as early as July, according to some forecasts.
How did El Niño affect southern Africa?
El Niño usually brings drought to southern Africa and the most recent version was true to form. Scorching heatwaves seared South Africa’s grain belt, with the harvest of the staple white maize 25% lower in 2024 compared with last year.
South African farmers’ intentions to plant winter wheat are down 3% compared with the size of the area devoted to the crop last year.
Neighbouring countries have been hit harder, not least because small-scale subsistence farming accounts for most of their agricultural production. Zimbabwe’s maize crop is forecast to be 72% lower, Bloomberg reported this week.
Zambia has declared a national disaster and appealed for close to $1-billion in aid following its driest summer growing season in more than 40 years.
The Kariba Dam is less than 14% full, creating power shortages in Zimbabwe and Zambia.
Some agricultural sectors have emerged relatively unscathed. South Africa’s citrus growers are forecasting record exports of 181.7 million cartons in 2024, a roughly 10% increase from last year’s historic high of 165.1 million.
Elsewhere, the latest El Niño slammed citrus, cocoa and coffee crops, sending futures prices for all of these commodities soaring – a trend reflected in retail prices.
What to possibly expect from La Niña
The Little Girl, by contrast, typically heralds good rains in southern Africa, and the previous prolonged one helped South African maize farmers produce three straight bumper harvests.
So, the 2024/25 summer should be wetter than 2023/24, and that should be favourable for maize and other summer crops, while dam levels should replenish.
But there is also a risk of too much rain, which is not good for grain.
Elsewhere, La Niña can lead to more intense Atlantic hurricanes which menace the east coast of North America and the Caribbean during the northern hemisphere’s summer and early autumn. But it tends to take the wind out of hurricanes in the eastern Pacific Ocean.
The effects of climate change
The ENSO cycle is natural but it has gone on steroids since South American fishermen first observed its consequences in the 17th century.
Human-caused greenhouse gas emissions are making both patterns stronger and more frequent, research has shown.
Hopefully for southern Africa, La Niña will produce a wet summer this year. Because the region will need plenty of moisture in the soil and topped-up dam levels to help it weather the next El Niño. DM