Analysis of 1,000-year-old coral records suggests that rising global temperatures are driving increased variability and intensity in the El Niño Southern Oscillation (ENSO) cycle.
Key facts
- •Coral records from the Galapagos Islands were used to reconstruct a 1,000-year history of Pacific sea surface temperatures.
- •ENSO cycle variability has increased by 36.5 percent over the last 40 years compared to pre-industrial levels.
- •The current El Niño is projected to reach sea surface temperatures 4°C above normal, a 60 percent increase over the previous record.
- •The past decade has seen three major El Niño events, a sequence not observed in records dating back to the late 19th century.
- •Mark Cane of Columbia University stated there is better than a 50-50 probability that climate change is influencing El Niño activity.
Researchers led by Julia Cole at the University of Michigan have found evidence that El Niño events are becoming more intense as global temperatures rise. By analyzing the chemistry of living and dead corals from the Galapagos Islands, the team constructed a 1,000-year record of sea surface temperatures in the eastern Pacific. The findings indicate that the ENSO cycle, which drives El Niño, has experienced a significant increase in variability over the last four decades compared to pre-industrial times.
By the numbers
Coral Chemistry as a Climate Proxy
To overcome the limitations of observational records that only date back to the 1980s, the research team used uranium and thorium dating to age coral samples. The chemical composition of the coral skeletons acts as a proxy for historical sea surface temperatures, allowing scientists to track fluctuations in the ENSO cycle over the past millennium. This method provides a long-term perspective necessary to distinguish climate-driven trends from natural environmental variability.
Increased ENSO Variability
The study revealed that variability in the ENSO cycle has increased by 36.5 percent over the past 40 years relative to the pre-industrial period. This shift is primarily attributed to more intense El Niño events. While the coral data covers approximately 500 years of the 1,000-year study period, researchers believe the trend clearly tracks with rising global temperatures.
Implications for Future El Niño Events
Experts note that recent El Niño events, including those in 2015, 2023, and 2026, align with the identified trend. Projections for the current El Niño suggest that sea surface temperatures in the east-central Pacific could reach 4°C above normal, representing a 60 percent increase over previous records. Michael McPhaden of the NOAA highlighted that the occurrence of three major El Niños in the past decade is unprecedented in the instrumental record dating back to the late 19th century.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by New Scientist.
