The 2015-16 El Niño: Climate Impacts in a Warming World

Published: May 16, 2026 · 8 min read

A Super El Niño on a Warmer Planet

The 2015-16 El Niño was one of the three strongest events in the instrumental record, rivaling the 1982-83 and 1997-98 Super El Niños in terms of peak sea surface temperature anomalies. But it occurred in a world that was measurably different from its predecessors. Global average temperatures in 2015 and 2016 had been pushed to record levels by the combination of El Niño-driven heat release and the long-term warming trend from greenhouse gas accumulation. The result was an event that, while similar in many physical respects to earlier Super El Niños, produced impacts that were amplified by the warmer baseline climate.

2016 remains the hottest year on record globally, and the El Niño contributed roughly 0.1-0.15 °C to the annual anomaly above and beyond the background warming trend. This compounding effect made the 2015-16 El Niño a preview of the types of extremes that could become more common if climate change continues unabated.

Evolution: A Slow Build to a Powerful Peak

The 2015-16 El Niño evolved differently from the rapid-onset 1997-98 event. Weak El Niño conditions first developed in early 2015 but stalled during the Northern Hemisphere spring, leading some forecast models to predict a weak-to-moderate event. However, a series of westerly wind bursts in the late spring and summer of 2015 triggered a sequence of Kelvin waves that reinvigorated the warming. By November 2015, the Niño-3.4 index reached +2.6 °C, tying the 1997-98 peak. The event was classified as a "Super El Niño" — defined by an ONI value of +2.0 °C or greater for at least one three-month season.

One notable feature was the eastward extent of the warming. While the 1997-98 event had maximum anomalies centered in the eastern Pacific (Niño-1+2 region), the 2015-16 event had its strongest anomalies in the central Pacific (Niño-3.4 and Niño-4 regions). This central-Pacific flavor produced teleconnection patterns that differed in important ways from the canonical eastern-Pacific El Niño, with implications for the global impact distribution.

2016: The Hottest Year on Record — and El Niño's Role

Global average surface temperature in 2016 was approximately 1.0 °C above pre-industrial levels, surpassing 2015's record by roughly 0.12 °C. El Niño contributed to this record through two mechanisms. First, the eastward shift of Pacific warm pool waters reduced the efficiency with which the tropical ocean releases heat to the atmosphere, leading to a net transfer of heat from ocean to atmosphere. Second, the suppressed cloud cover and rainfall in the western Pacific allowed more solar radiation to reach the surface, further warming the region.

The combined effect of El Niño and background warming produced extreme temperature anomalies in regions far from the tropical Pacific. The Arctic experienced winter temperatures 2-3 °C above the 1981-2010 average. Alaska recorded its warmest winter on record. Southern Africa, India, Southeast Asia, and Australia all experienced severe heatwaves that were exacerbated by the El Niño-induced drought conditions.

Coral Bleaching: The Great Barrier Reef's Worst Year

Perhaps the most devastating impact of the 2015-16 El Niño was on the world's coral reefs. Elevated ocean temperatures driven by the combination of El Niño warming and long-term climate change triggered the third recorded global coral bleaching event, which began in 2014 and extended through 2017. The Great Barrier Reef was hit particularly hard: during the austral summer of 2015-16, sea surface temperatures in the Coral Sea were 1-2 °C above the summer maximum, and the resulting bleaching affected over 90% of individual reefs within the Great Barrier Reef Marine Park.

Severe bleaching — where more than 60% of corals on a reef were bleached — affected the northern third of the Great Barrier Reef, from Cairns to the Torres Strait. Surveys conducted by the Australian Research Council's Centre of Excellence for Coral Reef Studies found that 30% of corals on the Great Barrier Reef died during the 2016 bleaching event. The mortality was depth-dependent: shallow-water corals, particularly branching Acropora species, suffered the highest losses.

The 2015-16 coral bleaching event was a stark demonstration of how El Niño and climate change interact. While El Niño alone would have elevated ocean temperatures, the background warming trend meant that the absolute temperatures experienced by corals during the event were substantially higher than during previous El Niño episodes. This was a clear example of the "compounding impacts" that are the most robust prediction of El Niño-climate change interactions.

Regional Impacts: A Different Pattern

Because the 2015-16 El Niño was a central-Pacific event, its regional impacts differed from the canonical eastern-Pacific pattern in several key respects:

The Americas. California received below-average rainfall during the 2015-16 winter, in contrast to the typical El Niño expectation of a wet southern U.S. The subtropical jet stream remained weaker and more northerly than during eastern-Pacific El Niño events, reducing the moisture transport into the region. Peru and Ecuador experienced less extreme flooding than during 1997-98, though heavy rainfall did occur. The Atlantic hurricane season was suppressed, consistent with all strong El Niño events.

Africa. Southern Africa experienced one of its worst droughts on record. The 2015-16 rainy season (October 2015-April 2016) brought significantly below-average rainfall to South Africa, Zimbabwe, Zambia, and Mozambique. South Africa's maize harvest fell by 25%, and the country was forced to import maize to meet domestic demand. Approximately 60 million people across southern and eastern Africa required food assistance as a result of the drought.

Asia and the Pacific. India's summer monsoon was deficient, consistent with the canonical El Niño-monsoon relationship. Indonesia and Papua New Guinea experienced drought and wildfires, though the intensity was less severe than 1997-98. The Philippines experienced a delayed onset of the rainy season, affecting agricultural calendars.

Advancements in Prediction and Response

Between 1998 and 2015, significant progress had been made in El Niño prediction capability. The 2015-16 event was forecast with reasonable skill by dynamical models as early as the spring of 2015, despite the stall that occurred mid-year. NOAA's Climate Prediction Center issued an El Niño advisory in March 2015 and maintained it through the event's peak. The event provided a valuable test of the operational forecast system and confirmed that multi-model ensemble predictions were more reliable than any single model.

The 2015-16 event also saw the first use of systematic climate threat assessments by humanitarian organizations, including the Red Cross and the U.N. Office for the Coordination of Humanitarian Affairs. These assessments used seasonal forecasts to identify at-risk populations and preposition aid supplies before the impacts materialized, marking an important evolution from reactive humanitarian response to anticipatory action.

Explore more at the El Niño Guide — comprehensive climate science explained.