Breaking down the health effects of the El Niño-Southern Oscillation

Understanding how the El Niño-Southern Oscillation is affected by climate change

An analysis of El Niño and La Niña patterns from 1901 to 2020 suggests that anthropogenic warming—global warming caused by humans—has at least partly contributed to increased ENSO variability in recent decades. While ENSO increases the likelihood of droughts and flooding across different regions, researchers say these severe weather events are made more extreme by greenhouse gas emissions.

How jet streams and US weather are affected by the El Niño-Southern Oscillation

Jet streams are predominantly west-to-east air currents in the atmosphere that mark the boundary between cold polar air and warm tropical air, where cells of atmospheric circulation meet. By disrupting the location of these circulations on two- to seven-year cycles, ENSO alters the probability of droughts, floods, and above- or below-average temperatures across the US.

Mapping how the El Niño-Southern Oscillation affects weather patterns around the world

In the warm episode (El Niño), summers in India, Indonesia, Australia, and the Caribbean are drier than normal, while winters bring wetter, cooler conditions to the US Gulf Coast and warmer conditions to the Pacific Northwest. During the cold episode (La Niña), these are reversed, with India, Indonesia, and the southern Caribbean experiencing greater rainfall in the summers.

Compare various El Niño-Southern Oscillations using maps of atmospheric and ocean variables

Because the intensity of the phases in the cycle is sensitive to small variations in atmospheric and ocean conditions and depends on complex interactions between these two systems, no two El Niño or La Niña events are identical. This contributes to the variability in the length of each phase, which is why an ENSO can last as little as two years or as long as seven.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

The global impacts of the 1877 'super' El Niño and what could result from similar future events

The 1877 El Niño event lasted approximately 18 months, raised temperatures in the Niño 3.4 region of the equatorial Pacific Ocean by 2.7 degrees Celsius (4.86 degrees Fahrenheit) above average, and contributed to a global famine that killed more than 50 million people. Such events are expected to exacerbate drought-related risks to global food security, driving up food prices worldwide. (Some readers may experience a paywall.)

How scientists use data to anticipate the phases of the El Niño-Southern Oscillation

Sea-surface temperatures across various regions of the equatorial Pacific Ocean can be compared with ocean temperatures elsewhere in the tropics to identify anomalies that indicate where in the ENSO cycle Earth finds itself. The "Niño 3.4" region in particular—known as the Ocean Niño Index—is a key indicator of ENSO phase and intensity.

Learn about various ocean-atmosphere cycles impacting global weather patterns

Although the El Niño-Southern Oscillation is among the most impactful, the North Atlantic Oscillation strongly influences weather patterns in the Northeast US by periodically changing atmospheric pressure over the Atlantic. The North Pacific Oscillation fluctuates atmospheric pressure and sea-surface temperatures that affect winter temperatures over much of the US.

Comparing La Niña and El Niño atmosphere-ocean feedback patterns

During La Niña, trade winds reinforce the flow of warm ocean water from the eastern to the western Pacific, allowing colder subsurface water in the eastern Pacific to rise to the surface. These changes reinforce overhead air movements by altering the air temperature near the ocean surface. During El Niño, these trade winds weaken or reverse, preventing upwelling by shifting warm water back to the eastern Pacific and displacing atmospheric circulation patterns.

Watch a visualization of how Earth's oceans impact its atmosphere, weather, and climate

Data from NASA satellites help view and explain global climate and weather patterns, such as El Niño and La Niña.

El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

Climate change is influencing the spread of disease

Rising temperatures and water levels are forcing animals and pathogens beyond their typical boundaries. This article and its data visualizations explore the proliferation of climate-driven diseases.

A medieval warm period reshaped agriculture across parts of the world

Between 750 and 1350 CE, some regions experienced temperatures that rivaled or exceeded late-20th-century averages, likely due to shifts in El Niño–La Niña cycles. The warmer, wetter climate in Europe and northeast North America boosted agriculture, while causing droughts elsewhere.

Climate shifts are projected to cause more cases of food poisoning

Research published in 2024 suggests that with more severe heatwaves and natural disasters, scientists expect there to be a rise in foodborne disease, especially in Africa and Asia. Already, there are an estimated 600 million food poisoning cases and 420,000 deaths annually. Diarrhea is the most common cause of those deaths.

Monsoons are large, seasonal shifts in wind driven by land-sea heating differences

Because land heats and cools faster than water, pressure differences form and create significant sea breezes. Moist air pulled onto land rises, condenses, and leads to substantial summer rainfall.

The impacts of the solar maximum on Earth, from telecommunications to auroras

During the peak of the sun's 11-year cycle, plasma emissions stronger than the average stream of particles from the sun can compress and distort the Earth's magnetic field, allowing auroras to be seen farther from the poles. Distortions in the ionized layer of Earth's atmosphere can also alter the path of communication transmissions through the air. (Some readers may experience a paywall.)

Measles reached global transmission during the 15th- and 16th-century Columbian exchange

Devastating diseases like smallpox, influenza, measles, and other viruses were largely introduced into the Western Hemisphere beginning with the 1492 arrival of Christopher Columbus and the ensuing age of exploration.

'Sloth fever' is an emerging health threat, especially to pregnant women

This disease, caused by the Oropouche virus, is found in animals including sloths, primates, and birds. It primarily spreads through the bite of midges—insects commonly called "no-see-ums." It's endemic to the Amazon region, but US travelers are increasingly contracting it internationally.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

See how the Ebola virus affects blood circulation in the human body

Ebola infects and disables immune cells, causing a cascade of events that result in small blood clots throughout the body, weakening blood vessels, and interrupting blood flow to key organs.

Three Ebola species are responsible for most large outbreaks of the disease, yet the only approved Ebola vaccine is known to work against just one of them.

The science of spring fever

Researchers have confirmed what people have sensed for ages: Our emotions during the springtime can go a little wild. This piece breaks down the impact of the seasonal transition on our bodies and prescribes a few ways to mitigate the effects.

Seasonal allergies don't always show up in childhood

The human immune system may become sensitized to pollen and develop an allergic reaction to it after prolonged exposure. Other triggers for new seasonal allergies may include exposure to new environments and changing climate conditions that affect allergy season length and conditions for various pollens.

B2 models the interactions of air, water, soil, plants and microbes at the LEO

The Landscape Evolution Observatory at Biosphere 2 examines how factors such as climate change, water flow, weathering and community development impact landscape structures comprising 500 metric tons of crushed rock. Research is also conducted at biomes representing savannas, mangroves, coastal fog deserts, oceans and rainforests.

Secondary complications from measles in children range across the whole body

The most serious effects of a measles infection, particularly in young children, come from its attack on the immune system. This leaves the whole body vulnerable to follow-on diseases, with some of the most serious including respiratory conditions, encephalitis, and more.

The Köppen-Geiger system divides Earth’s climate into five main categories

This classification system, developed by a German-Russian botanist and a German climatologist, results from differences in the intensity of solar radiation and rainfall in different parts of the world. Each category is further divided into multiple coded zones.

Malaria comes from the Italian term 'mal'aria,' meaning 'bad air'

The term refers to marshy areas associated with the disease. An estimated 94% of malaria cases—215 million—occur in Africa.

MS risk is shaped by geography, not just genes

Latitude—and related vitamin D exposure—seems to affect MS risk. People who migrate from a high-risk MS latitude (like northern Europe or the northern US) to a lower-risk latitude (like tropical areas) before age 15 tend to adopt the lower risk of their new country—suggesting there's a critical window for environmental exposure.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Poison ivy will likely become both larger and more resilient due to climate change.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Fireworks-related ER visits are on the rise—in 2024, they increased by 52% as compared to the prior year.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.

In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.