The Monsoon Paradox: How El Niño, Long a Harbinger of Drought, Is Now Linked to India’s Most Devastating Downpours 

This groundbreaking study reveals a critical paradox in the relationship between El Niño and the Indian monsoon, demonstrating that while El Niño still causes an overall seasonal drought by reducing total rainfall, it simultaneously increases the likelihood of devastating single-day extreme downpours in heavily populated regions like central and southwestern India; this occurs because El Niño alters atmospheric conditions to favor more intense, though potentially fewer, monsoon storms, a finding that upends over a century of conventional wisdom and opens vital opportunities for using seasonal El Niño forecasts to improve disaster preparedness for floods and save lives in vulnerable areas.

The Monsoon Paradox: How El Niño, Long a Harbinger of Drought, Is Now Linked to India’s Most Devastating Downpours 

For over a century, a fundamental tenet of climate science and Indian agriculture has been as reliable as the seasons themselves: when an El Niño event brews in the equatorial Pacific, India braces for drought. This correlation, etched into the minds of farmers, policymakers, and climatologists, has shaped everything from crop insurance policies to water conservation strategies. The equation was simple—El Niño equals a weak monsoon, which equals less rain. 

But what if that foundational wisdom, while correct in its broad strokes, was dangerously incomplete? What if the same climate force that starves the subcontinent of seasonal rainfall also supercharges the very storms that drown it? 

A groundbreaking new study published in the journal Science is forcing a dramatic rethink. Led by scientists at the City College of New York and Columbia University, the research unveils a disturbing paradox: while El Niño does indeed reduce the total rainfall during the Indian summer monsoon, it simultaneously increases the frequency of the most catastrophic single-day downpours in the nation’s most densely populated regions. It’s not a matter of less rain; it’s a matter of the rain falling in a more concentrated, violent, and destructive manner. 

Unraveling a Century-Old Assumption 

The research, led by Professor Spencer Hill of CCNY, upends a narrative that has held sway since the late 19th century. “We’ve known for over a century that El Niño events do precisely the opposite for total rainfall summed over the rainy season, June through September,” Hill acknowledges. The established mechanism is well-understood: El Niño, the warm phase of the El Niño-Southern Oscillation (ENSO), reorganizes global atmospheric circulation, typically leading to the formation of high-pressure systems that suppress the large-scale monsoon flow over India. 

“Our key finding is that you tend to get more days with extreme amounts of rainfall within India, not less, during El Niño summers,” Hill states. This counterintuitive discovery emerged not from a single new dataset, but from a sophisticated synthesis of over a century of rainfall observations, high-resolution modern data, and advanced atmospheric modeling. 

The critical breakthrough was in the methodology. Instead of lumping all of India’s vastly diverse climate zones into a single “Indian rainfall” bucket—a practice that can mask crucial regional differences—the team analyzed the data with a finer brush. 

“One key advance of our study’s approach is that, even though it deals with rare events, it allows robust differences to emerge,” explains co-author Michela Biasutti. “By doing so, we were able to see changes of the opposite sign in the rainiest and driest regions of the subcontinent.” 

The New Map of Monsoon Risk 

This granular analysis reveals a starkly divided India during El Niño summers. The map of risk has been redrawn: 

• The Danger Zones (More Extreme Rain): The increases in extreme daily rainfall are concentrated in two crucial belts: the heavily populated plains of central India and the southwestern coastal band, including parts of Maharashtra, Goa, and Karnataka. These are regions that have recently borne the brunt of devastating floods, such as those in Pune and Bengaluru. 

• The Relative Refuge Zones (Less Extreme Rain): Conversely, the southeastern and northwestern parts of the country, including Tamil Nadu and parts of Rajasthan, show the opposite signal. Here, the classic El Niño effect holds true, with a lower likelihood of both total seasonal rain and extreme daily deluges. 

This geographical schism explains how the two seemingly contradictory facts—less total rain but more extreme downpours—can coexist. The intense, concentrated bursts in central and western India are balanced out by a more profound and widespread dryness in other regions, leading to a net seasonal deficit. 

The Atmospheric Engine of Destruction 

So, how does El Niño manage this feat? The study delves into the complex atmospheric mechanics that turn a drought-maker into a flood-enabler. 

Think of the monsoon not as a uniform blanket of rain, but as a parade of distinct weather systems—the most potent of which are known as Monsoon Low-Pressure Systems (LPS). These are sprawling, rotating storms that travel across the subcontinent, acting as the primary delivery vehicles for the monsoon’s bounty. During a normal year, they provide steady, widespread, and beneficial rain. 

During an El Niño, however, the entire atmospheric environment changes. The large-scale monsoon current weakens, but the conditions in the mid-atmosphere over central India become peculiarly favorable for these LPS to intensify. The study suggests that El Niño alters wind shear and atmospheric instability in a way that acts like a steroid for these storms. While there might be fewer storms overall, the ones that do form are more likely to tap into deep tropical moisture and explode into torrential, slow-moving systems that dump staggering volumes of water in a short period. 

It’s akin to a traffic jam on a highway. El Niño doesn’t necessarily put more cars (moisture) on the road, but it creates chaotic conditions that cause a few drivers to slam on their brakes and cluster together, creating a massive, localized pile-up of rainfall. 

From Academic Insight to Lifesaving Forecasts 

The human and economic cost of this phenomenon is not theoretical. In 2024 alone, floods and extreme weather in India killed more than 3,000 people, destroyed or damaged 230,000 homes and buildings, and killed nearly 10,000 head of livestock. Urban centers, with their concrete landscapes and overwhelmed drainage systems, are particularly vulnerable to these sudden, intense cloudbursts. 

This is where the study transitions from a academic revelation to a tool with profound practical implications. The predictability of El Niño—with forecasts often available months in advance—opens a powerful window for preparedness. 

“Our results open the door to creating seasonal outlooks for extreme events in India, based on the slowly evolving temperature of the ocean,” says Biasutti. 

Imagine the potential: 

• Disaster Management: State governments in central and western India could, with greater confidence, pre-position emergency relief supplies, sandbags, and rescue equipment ahead of the monsoon season. 

• Infrastructure: Municipalities could accelerate the cleaning of storm drains and reinforce vulnerable river embankments in anticipation of a higher probability of extreme events. 

• Agriculture: Farmers, while aware of a potentially drier overall season, could also be warned about the heightened risk of crop-destroying flash floods, allowing for different planting strategies or crop insurance decisions. 

• Public Awareness: Early and targeted public awareness campaigns could be launched, warning communities of the specific risk of short-duration, high-intensity rainfall. 

The Larger Climate Context and the Road Ahead 

This research also casts a long shadow toward the future, particularly in the age of climate change. While this study focused on natural variability (ENSO), the physical mechanisms it uncovered are highly relevant to understanding how anthropogenic global warming is altering the monsoon. 

A warmer atmosphere holds more moisture—about 7% more per degree Celsius of warming. This basic law of physics is already intensifying rainfall extremes across the globe. The interaction between this background trend and the newly discovered El Niño dynamic suggests a potential “double whammy” for regions like central India. During future El Niño years, the natural propensity for more extreme downpours could be powerfully amplified by a warmer, wetter atmosphere, leading to rainfall events of unprecedented ferocity. 

The scientific journey is far from over. Professor Hill and his team have secured a new three-year grant from the National Science Foundation to dig deeper. “We will investigate how and why the type of storms responsible for much of this extreme rainfall, called monsoon low-pressure systems, change depending on whether there are El Niño or La Niña conditions,” he says. 

This work, building on the legacy of Lamont’s Mark Cane, who co-developed the world’s first El Niño model in the 1980s, continues to refine our understanding of one of Earth’s most vital climate systems. The old, simple story of El Niño and the Indian monsoon is gone, replaced by a more complex, nuanced, and urgent narrative. It’s a story that warns us that a changing climate doesn’t just turn the rain off; it can also, terrifyingly, turn the tap on full blast. Recognizing this paradox is the first critical step toward building a more resilient future for over a billion people.