The dynamics between La Niña and El Niño, two opposite phases of the El Niño-Southern Oscillation (ENSO) cycle, are driven by ocean temperature changes in the Pacific. La Niña cools the surface waters, leading to increased Atlantic hurricanes, droughts in the southern US, and wetter conditions in Southeast Asia. El Niño, with its warming effect, brings drier conditions to Southeast Asia and Australia, and wetter winters to southern U.S. and South America.
As climate change accelerates, these natural cycles are likely to become more intense and unpredictable. Warmer global temperatures will amplify the effects of both La Niña and El Niño, creating more extreme and frequent weather events. For instance, El Niño could cause even hotter and drier conditions, exacerbating wildfires and droughts, while La Niña could result in more intense storms and flooding. Furthermore, the shifting of weather patterns under climate change could lead to longer or more frequent ENSO cycles, creating a cascading effect on agriculture, infrastructure, and ecosystems.
Additionally, warmer ocean temperatures may modify how these patterns distribute their effects across the globe. For example, regions that traditionally experience heavy rains during El Niño may see even higher levels of precipitation, while dry areas could suffer from more intense droughts. The overall unpredictability of ENSO’s timing and magnitude is expected to increase, complicating preparedness and adaptation strategies for governments, industries, and communities.
El Niño’s Effects in 2024
This year, the transition to El Niño brought several extreme weather events around the globe.
Particularly in North America, the arrival of El Niño in 2024 has reversed some La Niña-driven droughts in the U.S. Southwest, especially in California, where heavy rains eased years of water shortages. However, this has also led to severe flooding in many regions and a surge in mudslides due to the parched, fragile soils from prior dry seasons. At the same time, southern states like Texas and Louisiana experienced intense heatwaves, with record-breaking temperatures and drier conditions exacerbating wildfire risks. Meanwhile, the Northeast and Midwest experienced cooler summers and wetter conditions than average, leading to agricultural delays.
Despite El Niño typically suppressing Atlantic hurricanes by increasing wind shear, Florida still experienced a high number of storms in 2024 due to several factors. First, the Atlantic Ocean was unusually warm, with sea surface temperatures reaching record highs. Warm waters provide the fuel hurricanes need to form and strengthen. Additionally, while El Niño was present, its wind shear effects were less dominant in the early part of the hurricane season. This allowed more storms to develop and make landfall in Florida than would normally be expected during an El Niño year.
Key factors include:
- Warmer Ocean Temperatures: Record-high sea surface temperatures in the Atlantic created optimal conditions for hurricane formation, allowing more storms to intensify quickly.
- Weakened El Niño Impact: El Niño’s influence, which usually limits hurricane activity by increasing wind shear, had a delayed effect this season. Early in the hurricane season, wind shear wasn’t strong enough to prevent storm development.
This combination of factors led to an unusually active hurricane season for the Southeast US region.
El Niño and La Niña have profound effects on global weather patterns. In 2024, the transition from La Niña to El Niño triggered a series of weather extremes, from record-breaking heatwaves to devastating floods. These climate patterns underscore the interconnectedness of our world’s weather systems and highlight the importance of understanding and preparing for their impacts, especially in regions vulnerable to climate risk.
With El Niño expected to continue into 2025, these disruptive weather events may only grow more pronounced, pushing regions to adapt their agriculture, infrastructure, and disaster response systems.