A powerful El Niño is developing in the Pacific Ocean, and the first major test of how severe its effects will be could arrive as soon as early June, when monsoon season begins across much of the tropical world.
Scientists are warning that this year’s weather pattern has the potential to be significantly disruptive and, crucially, unpredictable in ways that make planning difficult for the billions of people whose food security, water supply and daily lives depend on reliable monsoon rainfall.
“It’s going to be a very rough period,” says Jon Gottschalck, chief of the operational prediction branch at NOAA’s Climate Prediction Center. “Right now it looks like there will be considerable negative impacts in many of the tropical monsoon regions across the globe.”
The El Niño developing in the Pacific is expected to be basin-wide, meaning its warming will likely affect monsoon systems in India, Indonesia and West Africa simultaneously rather than concentrating its disruption in a smaller geographic area.
That scope makes this year’s forecast one of the more consequential in recent memory, in a climate system that has been increasingly difficult to predict.
What Is El Niño?
El Niño is one of Earth’s most powerful recurring climate phenomena. It occurs every two to seven years when the central and eastern equatorial Pacific Ocean warms significantly, an event that does not stay local but reshapes atmospheric patterns across the entire planet.
The mechanism is specific. The warmer water pulls rainfall toward that patch of sea and away from other parts of the world, says Spencer A. Hill, an assistant professor at the City College of New York who researches the dynamics of Earth’s monsoons.
When the Pacific pulls moisture toward itself, that moisture is no longer available to fall where the world’s monsoon-dependent populations expect it.
The Caribbean gets less rainfall. Indonesia gets less rainfall. Australia gets less. India, whose population of 1.4 billion people depends on the summer monsoon for a substantial portion of its annual water supply, gets less rainfall.
Typically, El Niño dries out parts of the planet, bringing less rainfall and warmer temperatures to places including the Caribbean, Indonesia and Australia.
India in particular sees less rainfall during El Niño summers. Already, India’s meteorological department has forecast a below normal monsoon season, adding that it was carefully monitoring sea surface temperatures in the Pacific.
India’s monsoon is not merely a weather event. The biggest and most famous monsoon accounts for 90 percent of total annual precipitation in some parts of the country.
A weakened Indian monsoon does not produce a slightly drier summer. It produces a cascade of consequences, for agriculture, for river levels, for the groundwater recharge that sustains wells through the dry season, for the crops that billions of people in South Asia depend on for their food supply.
The Paradox That Makes This Year Harder To Predict
If the story of El Niño were simply that it rains less when El Niño is active, planning around it would be difficult but manageable.
The research emerging from scientists like Spencer Hill suggests the actual dynamic is considerably more complicated, and more dangerous.
Hill and other researchers concluded that while total rainfall consistently declines in India during El Niño, extreme rainfall paradoxically increases.
In practice, that means the problem is not simply less water but the wrong kind of water arriving at the wrong times.
A season that delivers fewer total millimeters of rainfall but concentrates them in intense burst events is more destructive than a season that delivers the same fewer millimeters steadily.
Crops need consistent moisture distributed across growing periods. Infrastructure was built to handle average rainfall rates.
Soils that have been dried by a weak early monsoon become hard and brittle, less capable of absorbing water when it does arrive, more prone to runoff, more vulnerable to landslides when extreme rainfall events occur.
“Way too much rainfall could be devastating,” says Hill, causing landslides and floods especially in a place experiencing dry weather that yields loose, brittle soil.
The agricultural consequences of erratic monsoon patterns are some of the most serious in the climate science literature. Gottschalck notes that if you have rainfall you can expect to continue over the whole season, all your options remain open.
When there is a more erratic monsoon, it really increases a tremendous uncertainty in water resource and agricultural management.
Crops can start off well and then be completely dried out before harvest. Flooding at the start of the season can delay planting past the optimal window.
The compounding uncertainties of an erratic monsoon make agricultural planning nearly impossible, with consequences that extend from the individual farmer who loses a crop to the global commodity markets that set food prices for billions of people.
The worst historical precedent is stark. In 1983, a weak monsoon linked with El Niño contributed to the largest worldwide crop failure in modern history.
The 1983 event remains the reference point that food security researchers cite when discussing the potential global consequences of a strong El Niño year, and the similarities to current conditions in the Pacific have not gone unnoticed.
What Happened Before Monsoon Season?
One of the less intuitive aspects of El Niño science is that the conditions preceding monsoon season can shape that season’s character as powerfully as the El Niño itself. Gottschalck made this point in terms that should reshape how people think about the current forecast.
“What happened in the winter and into the spring is actually just as important, if not more important, than the monsoon season itself,” Gottschalck says.
The reason is land temperature. Monsoons form because land heats faster than ocean, the temperature differential between continental and oceanic surfaces creates the pressure gradients that drive moisture-laden air from sea to land, where it rises, cools and falls as rain.
A winter and spring that left the land unusually warm and dry going into monsoon season means the land will heat even faster and more intensely when summer arrives.
That stronger heating creates stronger monsoon circulation potential, counterintuitively pushing against El Niño’s drying tendency in some regions.
In the American Southwest, which saw a dry and warm winter, the monsoon could still be powerful, with heavy, hazardous rain.
“Since it was so dry and there is no snow, the land is likely going to be heating up quicker, more intensely,” says Gottschalck. “And that could mean very strong monsoon circulation potential.”
The American Southwest monsoon, which brings summer rainfall to Arizona, New Mexico and neighboring regions, could be intensified rather than weakened by the same El Niño that is expected to diminish rainfall in India and Indonesia.
The same weather pattern producing opposite effects in different regions is the specific kind of global complexity that makes El Niño years both fascinating and frightening.
For India, less snow cover in the Himalayas can bring a stronger monsoon, even in El Niño years.
The Himalayan snowpack shapes the temperature gradient between the Indian subcontinent and the ocean, less snow means a warmer, drier land that heats faster and potentially drives stronger monsoon circulation, partially offsetting the Pacific warming’s drying effect.
Where Is The El Niño In The Pacific?
Not all El Niño events are equal, and the geographic center of the Pacific warming matters significantly for which regions feel the strongest effects.
The location of El Niño’s warming is critical to the strength of monsoons. If it is further east in the Pacific, it could have less of an effect on India’s monsoon.
The current developing event does not appear to be concentrated in the eastern Pacific. “Right now it looks like it is going to be a basin-wide event,” says Gottschalck, meaning the warming will probably affect monsoon systems in India, Indonesia and West Africa.
A basin-wide event, warming spread across the broad central and eastern Pacific rather than concentrated in a smaller area, is the type most associated with widespread global impacts. The 1997-98 El Niño, which remains one of the most severe in recorded history, was a basin-wide event.
Gottschalck notes it takes time for higher latitudes to feel the effects of El Niño. In the tropics, the impact is faster.
The regions closest to the equator, India, Indonesia, West Africa, the Caribbean, will feel the effects first and most intensely.
The full global impact, including effects on North American and European weather patterns, will develop over the coming months.
What Could Come Next
Beyond the immediate agricultural and water supply concerns, El Niño years are associated with a cascade of secondary effects. Drier conditions across large tropical areas mean more fuel for wildfires.
Hotter temperatures, combined with reduced cloud cover and humidity, increase heat wave risk.
The health consequences of both wildfire smoke and extreme heat disproportionately affect the most vulnerable populations in the most affected regions.
Hotter and drier summers, as well as the extreme rainfall events associated with the phenomenon, can devastate crops and the people who grow and eat them.
Scientists emphasize that it is too soon to characterize how strong this El Niño will be, the Pacific is still warming and the full strength of the event will not be clear until later in the season.
What is clear is that June’s monsoon arrivals will provide the first empirical evidence of how this year’s El Niño is interacting with the pre-existing conditions in each affected region.
The monsoon that begins arriving in early June across South Asia, West Africa and other tropical regions is not merely a weather event.
It is the beginning of an extended test of how billions of people, their food systems, their water supplies and their agricultural economies will fare under a climate pattern that history suggests will be disruptive, erratic and significantly harder to predict than a normal monsoon year.
