- How El Niño Alters Weather Patterns From Peru to Indonesia - August 29, 2025
- New Whale Species Identified From Fossils Dating Back 26 Million Years - August 21, 2025
- The World’s 10 Oldest Living Trees - August 19, 2025
The Giant Ocean Thermometer Disrupts Everything
Think of the Pacific Ocean as a massive bathtub stretching from South America to Asia. El Niño is the “warm phase” of a larger phenomenon called the El Niño Southern Oscillation (ENSO), with La Niña (“little girl”) as the “cool phase” alternative measured by unusual cooling in the eastern Pacific Ocean. El Niño is the most dramatic year-to-year variation of the earth’s climate. Every few years, this colossal system switches into overdrive, turning weather patterns upside down across continents. The pattern shifts back and forth irregularly every two to seven years, bringing predictable changes in ocean temperature and disrupting the normal wind and rainfall patterns across the tropics. When El Niño strikes, it doesn’t just change the temperature of one stretch of ocean – it cascades into a global weather disruption that leaves millions dealing with floods, droughts, and everything in between.
Peru’s Desert Becomes a Lake
In the boreal spring of 2023, an extreme coastal El Niño struck the coastal regions of Peru and Ecuador, causing devastating rainfalls, flooding, and record dengue outbreaks. What happened next was almost biblical in scale. The arid Sechura desert in northern Peru was submerged under a vast lake known as Lake La Niña, a phenomenon observed only during extreme El Niño events. The storm, the first tropical cyclone to hit the area in decades, was disorganized and lacked an eye, but it dropped record amounts of rain in semi-arid northern Peru on March 9, 2023. Pacasmayo received 13.7 centimeters of rain in a 24-hour period, and Chiclayo saw 8.7 centimeters. To put this in perspective, the Peruvian coastal region receives less than 1-5 cm of annual rainfall in the driest areas (1), rendering it one of the driest places on Earth.
The human cost was staggering. The floods earlier this year triggered an unprecedented dengue epidemic in Peru, reaching the highest per capita dengue fever rate in the Americas, with a historical record of more than 172,000 dengue cases and 287 deaths (as of July 3 of 2023, based on UN data). Tens of thousands of homes were destroyed by the flooding.
The Science Behind Peru’s Transformation
What made this particular El Niño so devastating was the perfect storm of conditions. Surface waters were roughly 6°C (10.8°F) warmer than usual offshore of Peru for that date, according to data from the Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) project. This pushed sea surface temperatures above 27°C (80°F), speeding evaporation, making the air more humid, and fueling the formation of tall convective clouds that produce downpours and thunderstorms. Observations and ocean model experiments reveal that northerly alongshore winds and westerly wind anomalies in the eastern equatorial Pacific, initially associated with a record-strong Madden-Julian Oscillation and cyclonic disturbance off Peru in March, drove the coastal warming through suppressed coastal upwelling and downwelling Kelvin waves.
Indonesia’s Rice Fields Turn to Dust
Halfway around the Pacific, Indonesia faced the opposite extreme. Indonesia’s National Disaster Management Agency (BNPB) reported 1,185 disasters between July and September 2023, of which majority are drought related. This number is significantly higher compared to the same period in 2022. BNPB monitoring in the period 14-21 September 2023, at least 166,415 people are experiencing a clean water crisis. They are spread across 53 sub-districts in 11 provinces. This number increased from the previous week (27 July-3 August 2023), where 19,581 people were recorded as experiencing drought.
Rice prices surged across Indonesia during the second half of 2023 as the effects of El Niño led to widespread crop failures. In December, President Joko Widodo ordered military personnel to help farmers plant rice in a bid to boost domestic production, and curb food price inflation.
When Farmers Queue for Water
On Buru Island in eastern Indonesia, the human drama unfolded in heartbreaking detail. Like many rice farmers here on Buru Island in Indonesia’s eastern Maluku region, 53-year-old Tamami set aside his field after the availability of water dried up. “There’s no rain,” Tamami told Mongabay Indonesia in Savana Jaya village. “The reservoir is empty because of the long dry season.” On Buru Island, Mongabay Indonesia spoke with farmers who described risks of conflict as water scarcity forced farmers to queue for access to water. “Due to this water shortage, rice planting in several rice fields has been delayed,” said Temok Karyadi, head of the Buru district agriculture department.
Indonesia’s meteorology agency, the BMKG, documented extremely low levels of rainfall in much of eastern Indonesia during the second half of 2023, including on the island where Sutiah and Tamami grow rice. From August to October, monthly rainfall in the Maluku region was consistently recorded in the low range of 0-100 millimeters (0-4 inches).
The Pacific’s Giant Weather Machine
El Niño is essentially a chain reaction, beginning in the equatorial Pacific Ocean and extending around the globe. In climate science, or climatology, this broad web of effects is called “teleconnections.” Normally, the trade winds reliably blow from east to west across the tropical Pacific, which pushes the warm surface water toward Indonesia and away from equatorial South America. The atmospheric component of ENSO is represented by changes in the Walker circulation, an overturning loop in the atmosphere over the tropical Pacific. Hallmarks of the Walker circulation include rising air, clouds, and rain over Indonesia; west-to-east winds high up in the atmosphere; sinking air over the eastern Pacific; and the near-surface, east-to-west trade winds.
During El Niño, this entire system reverses. La Niña’s signature is cooler-than-average surface water in the east-central tropical Pacific, stronger-than-average trade winds, more rain and clouds over Indonesia, and drier conditions over the central Pacific. El Niño is the opposite, with warmer-than-average surface water and weaker atmospheric circulation, while ENSO-neutral conditions are close to average.
Marine Life Gets Scrambled
According to NOAA fisheries, a big consequence of El Niño is a loss of commercially important species where they traditionally occur. In fact, the name “El Niño” was first coined by South American fishermen in the 1600s when they noticed lower abundance of fish during certain warmer years. The warmer Pacific surface water along the South American coast can drive certain fish species away from their normal range toward colder water. But while warmer temperatures drive away some fishery species like anchovy off the coast of Peru, it can also bring tropical species like yellowtail and albacore tuna into areas that are usually too cold.
In addition to the direct temperature changes, the reduction in trade winds also allows warm water to drift back toward the South American coast and reduces the process of “upwelling”. Upwelling brings up cold, nutrient-rich water from the lower layers of the ocean to the surface, where trade winds pushed away warmer water. Upwelling provides necessary nutrients for phytoplankton. Without upwelling, there are little to no phytoplankton, which means the ecosystem can no longer support the same productivity, resulting in ecosystem-wide effects.
Economic Chaos Across the Pacific
The economic ripple effects stretched far beyond agriculture and fishing. The increase of sea temperature linked to El Niño also reduced fishing catches in countries like Peru and Ecuador. Drought also has an impact on the trade sector, namely the occurrence of a surge in food prices. According to Dwikorita, drought also has an impact on the trade sector, which is the occurrence of a spike in food prices. The ACP says that El Niño has contributed to the severe drought. As the Panama Canal massively reduces the time and distance ships travel between the Pacific and Atlantic oceans, these cuts are expected to have increased the cost of shipping goods around the world.
Peru has set aside $1.06 billion to deal with El Nino’s impacts and climate change, while the Philippines – at risk from cyclones – has formed a special government team to handle the predicted fallout.
Global Temperature Records Shattered
As a result of record-high land and sea surface temperatures since June 2023, last year became the hottest year on record. This year could be even warmer, Talaas warns. “This is clearly and unequivocally due to the contribution of the increasing concentrations of heat-trapping greenhouse gases from human activities.”
A double-whammy of El Niño and long-term climate change hit Latin America and the Caribbean in 2023, according to a new report from the World Meteorological Organization (WMO). Drought, heat, wildfires, extreme rainfall and a record-breaking hurricane had major impacts on health, food and energy security and economic development.
Health Crisis Spreads Like Wildfire
The health impacts were devastating and often unexpected. According to one recent paper, this is associated with an increase in heat-related mortality of 140% from 2000-2009 and 2013-2022. In Latin America and the Caribbean, an estimated 36 695 annual heat-related excess deaths occurred between 2000 and 2019. Air pollution, often worsened by climate change, is a serious health threat, with over 150 million people in the LAC region living in areas exceeding World Health Organization (WHO) air quality guidelines.
Due to the high rate of dengue cases, on May 10 the Ministry of Health (MINSA) declared a health emergency in 20 out of 25 regions in the country. The flooding created perfect breeding conditions for disease-carrying mosquitoes, turning the weather disaster into a public health catastrophe.
