When we hear about extreme heat, drought, floods or unusual weather around the world, one name often appears in the conversation: El Niño.
But what exactly is El Niño, and why can warming water thousands of kilometres away in the Pacific Ocean affect the lives of people across the planet?
What Is El Niño?
El Niño is a naturally occurring climate pattern involving the Pacific Ocean and the atmosphere above it. It is the warm phase of a larger climate cycle known as the El Niño–Southern Oscillation, or ENSO.
Under normal conditions, easterly trade winds push warm surface water westward across the tropical Pacific toward Asia and Australia. This allows colder, nutrient-rich water to rise from deeper parts of the ocean along the western coast of South America.
During an El Niño event, those trade winds weaken. Warm water spreads eastward across the central and eastern tropical Pacific, ocean temperatures become unusually high, and the normal circulation of the atmosphere begins to change.
That shift can alter rainfall, winds, storms and temperatures thousands of kilometres away.
El Niño events generally occur every two to seven years and typically last around nine to twelve months, although some can continue longer.
How Can El Niño Affect People?
The most important thing to understand is that El Niño does not create the same weather everywhere. One country may experience drought while another experiences unusually heavy rainfall.
1. More Extreme Heat
El Niño tends to raise the Earth’s average surface temperature because additional heat from the tropical Pacific Ocean is released into the atmosphere.
For people, hotter conditions can mean greater risk of heat exhaustion, heatstroke, dehydration and cardiovascular stress, particularly for older adults, young children, outdoor workers and people with existing health conditions.
2. Drought and Water Shortages
El Niño can reduce rainfall in parts of Australia, Indonesia, southern Africa and South Asia.
Long periods without rain can reduce drinking-water supplies, damage crops, kill livestock and increase the likelihood of wildfires.
For communities that depend heavily on rain-fed agriculture, a failed rainy season can quickly become an economic and humanitarian crisis.
3. Floods and Landslides
The opposite can happen elsewhere.
El Niño is often associated with heavier rainfall in parts of South America, East Africa and the southern United States.
Extreme rainfall can lead to flooding, landslides, contaminated drinking water, damaged homes and disrupted transportation and health services.
4. Food Shortages and Higher Prices
Perhaps one of El Niño’s most significant human impacts occurs through agriculture.
Too little rain can destroy crops. Too much rain can do the same.
Past El Niño events have affected production of commodities including rice, coffee and cocoa. When harvests decline across important agricultural regions, the effects can travel through global supply chains and eventually appear as higher food prices for families living thousands of kilometres away.
The World Health Organization notes that ENSO-related droughts and heavy rainfall can threaten food security and contribute to malnutrition.
5. Increased Risk of Disease
Changing rainfall and temperature can also change conditions for disease.
Flooding may contaminate water supplies and increase the risk of waterborne illness. At the same time, changes in rainfall, humidity and temperature can create favourable breeding conditions for mosquitoes that transmit diseases such as malaria and dengue.
Drought creates different dangers by reducing access to clean water and sanitation.
6. Wildfires and Dangerous Air
Dry vegetation combined with extreme heat can create ideal conditions for wildfires.
Even people far from the flames can be affected because wildfire smoke contains fine particles capable of travelling hundreds or even thousands of kilometres.
Smoke exposure can aggravate asthma and other respiratory illnesses and can also increase cardiovascular risks.
Is El Niño Caused by Climate Change?
No. El Niño existed long before modern human-caused climate change.
Scientists consider it a natural part of Earth’s climate system.
However, there is an important connection.
The world is now considerably warmer because of greenhouse-gas emissions. El Niño temporarily adds additional natural warming on top of that already elevated temperature.
The World Meteorological Organization says there is currently no evidence that climate change is making El Niño itself more frequent or inherently stronger, but a warmer atmosphere and ocean can amplify some of its impacts, including extreme heat and intense rainfall.
Think of it this way:
Climate change raises the baseline temperature. El Niño can temporarily push temperatures and weather patterns even further away from normal.
Why El Niño Matters to All of Us
El Niño begins in the tropical Pacific, but its consequences do not remain there.
A change in ocean temperature can eventually influence food prices, health, water supplies, agriculture, wildfires, international trade and humanitarian emergencies on the other side of the world.
And the effects are not shared equally. Poorer communities, farmers dependent on rainfall, people without reliable cooling or clean water, children and older adults are often among those most vulnerable.
Every El Niño is different, and scientists cannot say that every flood, drought or heatwave is caused by it. But understanding El Niño gives governments and communities something extremely valuable: time to prepare.
Modern forecasting can often identify El Niño months before its strongest impacts arrive. That means countries can prepare water supplies, strengthen health systems, protect crops, plan for floods and issue heat warnings before emergencies develop.
As our climate continues to warm, understanding natural climate patterns such as El Niño is becoming increasingly important—not only for scientists, but for everyone whose food, health, home or livelihood depends on the weather.
El Niño may begin in the ocean, but its effects can eventually reach all of us.
Learn more about El Nino:
El Niño set to be 'strongest in living memory', says Met Office-BBC
Why scientists are worried about this El Niño | BBC News
Written by Sami Chowdhury | Toronto-based REALTOR® and community blogger covering climate change, extreme weather, real estate, and issues affecting Toronto and the Greater Toronto Area (GTA) | TorontoBased.com