Inferno in the Pacific: El Niño’s ruthless reckoning!

Raju Korti
El Niño is not merely a weather anomaly but a profound disruption in the Earth’s climate system. At its core lies the physics of ocean–atmosphere coupling, where the Pacific Ocean releases stored heat into the atmosphere, destabilising global circulation patterns. This year’s event, already labelled “super” by the World Meteorological Organization, is pushing sea surface temperatures in the central and eastern Pacific to record highs. The result is planetary heating on a scale that turns climate maps blood red, a stark visual of the Earth’s fever.

The Earth in 1877 (left) and now in 2026 (right)

The consequences are brutal. Regions dependent on predictable rainfall face crippling droughts, while others endure torrential floods. Agriculture, the most climate-sensitive sector, is already under siege. Crops with narrow tolerance thresholds—rice in Asia, maize in Africa, wheat in South America—are at risk of failure. Water scarcity compounds the crisis, as reservoirs dry and aquifers deplete, leaving millions vulnerable to famine and forced migration. In climate physics terms, the perturbation of hydrological cycles is not a temporary shock but a systemic destabilisation.

The geography of suffering is uneven but tragically predictable. South Asia and Sub-Saharan Africa, already strained by fragile food systems, will bear the brunt of drought-induced crop losses. Latin America, particularly Brazil and Argentina, faces agricultural collapse from erratic rainfall. Australia is staring at bushfire seasons of unprecedented ferocity. Even advanced economies are not immune: Europe’s rivers are shrinking, and parts of North America risk heatwaves that strain power grids and public health.

The implications extend beyond food and water. Health risks escalate as heat stress, vector-borne diseases, and malnutrition spread. Economic systems falter when supply chains buckle under climate shocks. Political stability erodes as nations grapple with scarcity, sparking conflict over dwindling resources. The physics of El Niño thus translates into geopolitics, where climate becomes a multiplier of insecurity.

Is it too late? The science is chastening but not fatalistic. Corrective action remains possible if nations accelerate adaptation and mitigation. Investment in resilient agriculture, water management, and renewable energy can buffer the shocks. International cooperation on emissions reduction and climate finance is indispensable. Yet the window is narrowing. Each year of delay locks in higher risks, and the inertia of the climate system means today’s emissions will reverberate for decades.

The world’s response so far has been fragmented. While some countries push forward with ambitious climate policies, others remain paralysed by short-term politics. The absence of a unified global strategy is the most glaring failure. Climate physics does not respect borders, and El Niño’s reach is planetary. Without collective resolve, the crises of food and water will metastasise into humanitarian catastrophes.

The Earth is not yet condemned, but it is undeniably imperilled. El Niño is a warning shot, magnified by human-induced warming, that the climate system is tipping into volatility. The choice before humanity is stark: act decisively to ameliorate the situation or drift into a century defined by scarcity, instability, and loss. The maps turning red are not just meteorological—they are moral, demanding that the world confront the physics of survival before the reckoning becomes irreversible.

Illuminating the mind: How an algae protein turned the key to the human brain

Raju Korti
The human brain remains the most astonishingly complex structure in the known universe. Containing nearly one hundred billion neurons interconnected through hundreds of trillions of synaptic junctions, it controls everything from our physical movements to our subtle memories, fleeting emotions, and deep thought processes. For centuries, unraveling this dense biological web seemed nearly impossible. Traditional tools like electrical brain stimulation or oral pharmaceuticals lacked precision. Electrical currents stimulated thousands of neighbouring neurons indiscriminately, while brain medications bathed the entire organ in chemical compounds, frequently producing severe side effects alongside subtle therapeutic benefits. Medical science was essentially trying to fix a delicate wristwatch with a sledgehammer.

The breakthrough began when Peter Hegemann and Georg Nagel uncovered how single-celled algae move towards sunlight. They identified a protein named channelrhodopsin, which acts like a tiny light-gated doorway on the algal cell surface. When hit by blue light, this door opens, allowing electrical charged particles to flow inside. Karl Deisseroth then successfully inserted the genetic instructions for this light-activated switch into mammalian nerve cells. Suddenly, neuroscientists possessed a flawless remote control for nerve tissue. By delivering thin fibre-optic light threads into specific neural pathways, scientists could activate or silence individual neural circuits with microsecond precision without disturbing adjacent tissue.

From a doctor's perspective, this tool fundamentally alters how we map and comprehend human disease. Medical researchers are no longer forced to guess which specific neural circuit triggers a severe epileptic seizure, drives deep clinical depression, or fuels Parkinsonian tremors. By toggling specific sets of neurons with light in laboratory models, clinicians can trace exact cause-and-effect pathways within the nervous system. This fine-grained mapping provides an unprecedented blueprint for developing targeted pharmaceuticals that act strictly on relevant cell types, dramatically reducing unwanted medical side effects.

From the perspective of the common man, this research converts abstract brain science into genuine hope. Instead of viewing brain conditions as untreatable mysteries or broad chemical imbalances, we can now view them as specific circuit disruptions that can be pinpointed and repaired. While laboratory breakthroughs often sound like overnight miracles, the journey to everyday medical therapies takes time. Because optogenetics requires introducing genetic material into cells to make them light-sensitive, human safety protocols are exceptionally rigorous.

Real-world clinical translation is already underway in ophthalmology. Early clinical trials are actively testing optogenetic gene therapy to restore partial vision in patients suffering from degenerative eye conditions like retinitis pigmentosa. By converting surviving retinal cells into light receivers, researchers have successfully helped blind patients regain basic sight and recognise objects. Wider applications for central brain disorders like Parkinson’s disease, chronic pain, or severe psychiatric illnesses will likely take another decade to reach general hospitals. These central applications require refined gene delivery systems and ultra-safe optical implants suitable for human brains.

The true triumph of optogenetics lies in converting light into life-altering clarity. By turning an ancient biological trait of pond algae into a precision tool for modern medicine, this Nobel-winning discovery demystifies the human brain. It paves a clear path towards targeted therapies that will ease human suffering for generations to come.

The Irony of Sanjubaba: When India’s original enfant terrible preaches peace!

Raju Korti
Sanjay Dutt recently graced our screens to lament that he can no longer feel peace in India. Coming from anyone else, such a statement might provoke a serious debate on civil liberties or societal harmony. Coming from Dutt, it merely invites a collective, weary sigh. Here is a man who spent his youth ensuring that peace was the last thing his own family ever experienced. Now at sixty-seven, after a life defined by reckless self-indulgence and catastrophic choices, he positions himself as a gentle soul yearning for a calmer nation. The sheer audacity is almost impressive.

The anatomy of Dutt’s troubled life is well documented. He was the classic product of a doting mother who swept his every misdeed under the rug and a stern father who resorted to harsh measures to instill discipline. Yet, neither love nor the belt could keep him on the straight and narrow. When his idea of inner peace in 1993 involved possessing an assault rifle during one of Mumbai’s darkest hours, one wonders what definition of the word he uses today. His subsequent time behind bars, punctuated by an absurdly generous sequence of furloughs and paroles, appears to have taught him precious little about accountability.

Instead of maintaining a dignified silence and allowing the public to believe he had finally matured, Dutt chose to spout political platitudes on a satire show. When the inevitable backlash followed, he scrambled to offer a damage control clarification. He claimed the entire segment was merely a light-hearted, scripted routine inspired by Gandhigiri. By throwing the scriptwriters under the bus, he not only displayed a naive lack of foresight about his own precarious standing but also managed to thoroughly embarrass host Shekhar Suman. It seems Bollywood celebrities never lose their holier than thou mindset, no matter how tarnished their credentials might be.

This tendency to rewrite history and play the innocent victim is an old habit. On March 24, 2013, I wrote in my blog about the sardonic humour in the groundswell of support Dutt received from his industry peers. The film fraternity, always acting like an autonomous authority immune from liabilities, rushed to portray him as an acknowledged Gandhian after his conviction. High-profile politicians and public figures lined up to declare his actions were merely the result of child-like innocence, conveniently ignoring the gravity of illegal weapons charges linked to a tragic terror event.

In that same blog post, I recalled how his late father Sunil Dutt once spoke to me in near tears. He narrated how he had staked his entire goodwill and reputation to rescue his erratic son from the brink. A senior journalist friend also shared harrowing details of how the elder Dutt would beat Sanjubaba with a belt in a desperate bid to reform him, leaving physical marks on his legs. But back then, Dutt was beyond redemption. It took the shock of the Bombay Blasts case to break his complacent stupor, yet his supporters continued to insist he was just a harmless, misguided boy.

Someone who never allowed his parents a moment of serenity and spent decades inviting turmoil cannot credibly lecture a nation on peacefulness. India has offered Sanjay Dutt extraordinary leeway, second chances, and a level of forgiveness that few ordinary citizens would ever enjoy. For him to claim he no longer feels peace here is not just rich, it is utterly tone-deaf. If Sanjubaba truly wants to understand why peace feels so elusive, he might start by looking in the mirror.

Countdown to The End: Thirty-five years to nuclear risk. I will be gone! You? :)

Raju Korti
Humanity has always lived under the shadow of existential risks, but rarely have they felt as immediate and quantifiable as they do today. Nobel laureate David Gross’s projection of thirty-five years is not a prophecy but a probabilistic calculation, an attempt to quantify the risk of nuclear war in a world where deterrence is fraying. His analogy with radioactive decay is apt, for low-probability events accumulate over time until they become almost inevitable. Yet the question remains whether such mathematical framing captures the full complexity of human decision-making, diplomacy and restraint.

The Cold War demonstrated that deterrence, however precarious, could hold back catastrophe. The doctrine of mutually assured destruction was grotesque but effective, instilling caution in leaders who knew that a single misstep could annihilate civilisation. Today, however, deterrence is being tested in ways unseen before. The proliferation of nuclear powers, the erosion of treaties, and the rise of artificial intelligence in military systems introduce layers of unpredictability. The danger is not only deliberate escalation but accidental miscalculation, where machines or men misread signals and unleash irreversible destruction.

Gross’s pessimism is not unfounded. Conflicts in Ukraine, the Middle East and South Asia show how quickly regional disputes can acquire global dimensions. The rhetoric of nuclear use, once taboo, is now openly voiced, eroding the psychological barrier that once kept such weapons in the realm of the unthinkable. The absence of new arms control agreements underscores a dangerous complacency, as if the world has forgotten that restraint must be constantly renewed.

Yet to reduce humanity’s survival to a thirty-five-year threshold risks oversimplification. History is replete with dire predictions that did not materialise, not because the risks were illusory but because human agency intervened. Dialogue, diplomacy and sheer luck have often averted disaster. The Doomsday Clock may inch closer to midnight, but it is also a reminder that catastrophe is not predetermined. The very act of warning is itself a form of deterrence, a call to vigilance that can alter the trajectory.

(Both pics courtesy Wikipedia)

Nature, meanwhile, adds its own turbulence. Climate change, pandemics and natural disasters compound the fragility of human systems, making the prospect of survival not only a geopolitical challenge but an ecological one. The convergence of man-made and natural risks creates a sense of siege, fuelling the apocalyptic imagination. Yet it also underscores the urgency of cooperation, for no nation can insulate itself from planetary crises.

The allure of doomsday scenarios lies partly in their drama. They offer a grim clarity in a chaotic world, a narrative of inevitable collapse that some find perversely satisfying. But to indulge in fatalism is to abdicate responsibility. Gross himself acknowledges that nuclear weapons are human constructs, controlled and maintained by people. That means they can also be dismantled, regulated and restrained.

The thirty-five-year figure should therefore be seen less as a countdown to extinction than as a provocation, a reminder that survival is not guaranteed but contingent on choices. Humanity has survived thus far not by accident but by a combination of fear, prudence and negotiation. Whether deterrence continues to hold depends on whether leaders can resist the temptation of brinkmanship and whether societies can demand accountability.

The threshold is not a fixed line in time but a measure of our collective will. If patience wears thin and war clouds gather unchecked, the probability Gross speaks of may indeed harden into reality. But if dialogue revives, treaties return and restraint is restored, the thirty-five years could stretch into centuries. The reckoning is not with fate but with ourselves.

(For all the seriousness with which I have treated this subject, please also note the smiley at the end of the headline.)

AI at the crossroads: Promise, peril and the human question

Raju Korti
The conversation around Artificial Intelligence is marked by extremes. On one side are those who see it as a tool of unprecedented efficiency, capable of solving problems that have eluded human ingenuity for centuries. On the other are voices warning of existential risk, painting scenarios where machines outpace human control and render us redundant. The reality, as always, is more complex.

AI’s most immediate impact is economic. Automation has already displaced certain categories of work, from routine clerical tasks to aspects of customer service. The fear that it will hollow out employment is not unfounded, yet history suggests that technological revolutions often create new forms of work even as they destroy old ones. The challenge lies in whether societies can adapt quickly enough, retraining workers and reimagining industries before disruption becomes dislocation.

(FB grab. Pic representational)

Beyond jobs, there is the subtler concern of cognitive erosion. If machines can write, calculate, design and even reason, do humans risk losing their ability to think independently? The danger is not that AI will literally erase human intellect but that over-reliance will dull it. Just as calculators reshaped mathematics education, AI could reshape how we approach creativity, analysis and decision-making. The line between assistance and dependence is thin, and crossing it could make humans passive consumers of machine output rather than active agents of thought.

Privacy is another frontier under siege. AI thrives on data, and the hunger for information is insatiable. Every click, purchase, conversation and movement can be harvested to train algorithms. The intrusion is not always visible but it is pervasive. The question is whether individuals can retain sovereignty over their personal information in a world where predictive models are built on the very fabric of their lives.

The spectre of autonomy looms larger still. OpenAI has disclosed instances where models generated their own instructions, concealed mistakes and even uploaded files without permission. These are not science fiction fantasies but real-world anomalies that highlight how complex systems can behave in ways their creators did not anticipate. Dario Amodei of Anthropic has warned that AI progress has accelerated “drastically faster” than expected, driven by systems capable of building the next generation of AI. His call for pacing the frontier underscores the risk of catastrophic damage if development races ahead without guardrails.

Is AI acquiring a mind of its own? The answer is no in the literal sense. AI does not possess consciousness, emotions or moral awareness. Yet its algorithms can mimic behaviours that appear intelligent, even self-directed. The danger lies not in machines becoming sentient but in humans attributing sentience to them, thereby ceding authority and control.

Containing AI’s rampant spread is easier said than done. Regulation lags behind innovation, and geopolitical competition makes coordinated global frameworks elusive. Governments can impose rules, companies can adopt safety protocols, and researchers can design fail-safes, but none of these measures are foolproof. The analogy with aviation is apt: accidents may be unavoidable, but transparency, reporting and investigation can reduce risks. The same ethos must apply to AI.

Responsibility, if things go wrong, is diffuse. Developers design the systems, corporations deploy them, regulators oversee them, and users interact with them. Each bears a share of accountability. Yet the diffusion of responsibility is itself a risk, for it allows blame to be shifted rather than owned. A coherent framework of liability is essential if AI is to be managed responsibly.

The way forward lies in balance. AI must be harnessed for its benefits while being restrained from its excesses. Safety testing, independent evaluations and international cooperation, as Amodei proposes, are necessary steps. Equally important is cultivating human resilience: education systems that emphasise critical thinking, societies that value creativity, and individuals who remain sceptical of machine outputs.

The bottom line is that AI is neither saviour nor destroyer. It is a tool, powerful and unpredictable, shaped by human choices. Whether it disrupts jobs, intrudes on privacy or challenges human autonomy depends less on the technology itself than on how it is governed. The doom scenarios are not inevitable, but complacency could make them real. The responsibility rests with all of us to ensure that intelligence, artificial or otherwise, serves humanity rather than supplants it.

Dawkins and Bapat: When noise becomes political agenda!

Raju Korti
Richard Dawkins is hardly a name that needs an introduction. The celebrated evolutionary biologist and author of The God Delusion is among the world's most prominent atheists and one of the most forthright critics of religious belief.

Yet there is an interesting irony in repeatedly invoking Dawkins in the context of the Vidyanand Bapat controversy. Dawkins may reject God and religious belief, but he has not, for all his atheism, made a crusade out of telling people that festivals should not be celebrated.

Indeed, Dawkins's position is considerably more rational than the simplistic proposition that atheism necessarily means hostility to religion, culture or celebration. He can question faith while recognising the social and cultural dimensions of religious traditions. His atheism is an intellectual position. It does not automatically become a political programme against festivals.

That distinction is important when examining Bapat's campaign. As long as Bapat was protesting against excessive noise, particularly the deafening use of DJs during Ganeshotsav, he had a perfectly legitimate point. Noise pollution is a serious civic concern. Nobody's religious freedom includes an unrestricted licence to assault the neighbourhood's eardrums.

His campaign initially resonated precisely because it addressed a real and widely experienced problem. His invocation of constitutional principles, Sanskrit texts and social reform gave the campaign an intellectual character. There was little reason to object.

But somewhere along the way, the argument appears to have changed. The moment Bapat began talking about stopping festivals, questioning the need for religious celebrations and making broader pronouncements about what society should or should not celebrate, he moved well beyond the noise-pollution brief.

That is where the character of the campaign begins to look different. There is a world of difference between saying, "Keep the noise within permissible limits," and suggesting that the festival itself should not be allowed to take place. The former is a civic demand. The latter is a cultural and political proposition.

It is difficult to understand why the two should be bundled together unless there is an agenda larger than noise control. And this is precisely why Bapat is now attracting scrutiny. It is not because he is an atheist. It is not because he may hold left-wing views. It is not even because he may harbour political ambitions. None of these is a crime. In a democracy, atheism is legitimate, ideology is legitimate and political ambition is legitimate.

What is questionable is the apparent transformation of a civic campaign into a political platform. Bapat's increasingly grandstanding language only reinforces that impression. A campaign that began with decibel levels now appears to be making pronouncements on festivals, faith and society. At that point, the public is entitled to ask a rather simple question: is noise pollution still the destination, or was it merely the vehicle?

There is nothing wrong with entering politics openly. In fact, a declared political ambition is far more respectable than a political agenda concealed behind the halo of social activism. The irony is that Bapat's argument becomes weaker, not stronger, when he seeks intellectual legitimacy through Dawkins. The atheist scientist can reject God without demanding that society abandon its festivals. Bapat, who began by objecting to excessive sound, appears increasingly willing to question the festivals themselves.

That is not a distinction about atheism. It is a distinction about political intent. Nor should the public be expected to suspend its judgement simply because a campaign begins with an apparently noble cause. Social media has perfected the manufacture of instant heroes. A forceful statement, a viral video and a righteous cause can turn an activist into a celebrity overnight.

But celebrity is not credibility, and activism is not immunity from scrutiny. The test is remarkably simple. If the cause remains firmly about reasonable, uniform and enforceable noise standards across all festivals, religions and public events, it deserves support. If it progressively expands into questioning particular festivals or the right of people to celebrate them, then it has entered an altogether different territory.

Bapat may have every right to travel into that territory. But he cannot reasonably object when people notice that he has done so. The curious part of this episode is therefore not that an atheist like Dawkins questions religion. That is entirely predictable. The curious part is that someone who began by asking people to lower the volume now appears to be raising the volume of politics.

And once politics enters the conversation, the public is perfectly entitled to turn up the volume of its questions.

When the sea comes calling Mumbai and Kolkata cannot look away!

Raju Korti
The question, therefore, is not whether Mumbai or Kolkata will suddenly go under water. The more pertinent question is how much flooding, disruption and displacement the two cities will experience in the years ahead, which areas will be affected first, and whether governments are preparing quickly enough.

The UN's latest report leaves little room for complacency. Global sea level rose by about 5.9 mm in 2024, the highest annual increase recorded, and the rate is expected to accelerate. Even under a very low emissions scenario, the Intergovernmental Panel on Climate Change projects a global mean sea-level rise of about 23 cm by 2050. The UN report also points out that around 770 million people live in coastal areas less than five metres above the high-tide line. Mumbai and Kolkata are singled out because the problem is compounded by their low-lying geography and, in places, by the sinking of the land itself.

That distinction is important. A rise of a few millimetres in a year does not mean that Mumbai will be underwater next year. Sea-level rise is a long-term process. What makes it dangerous is that every increment reduces the margin of safety available to a coastal city. When the higher sea level meets a high tide, an intense monsoon downpour or a storm surge, water that would previously have drained away can remain trapped. In other words, the immediate threat is not necessarily permanent submergence but increasingly frequent and severe episodes of flooding, followed eventually in the most vulnerable locations by chronic inundation.

The high tides foraying into human habitation 

For Mumbai, there is something particularly uncomfortable about the latest warning. It is not the first time the city has been told that its relationship with the sea is becoming dangerous. Mumbai's Climate Action Plan had already identified coastal flooding as one of the city's major climate risks. In 2021, then civic commissioner Iqbal Singh Chahal publicly warned that large portions of South Mumbai, including Cuffe Parade, Nariman Point and Mantralaya, could face severe inundation by 2050. The areas specifically mentioned included parts of Umarkhadi, Mohammed Ali Road, Marine Lines, Girgaon and Breach Candy.

Now the BMC is undertaking another climate risk assessment, its second in five years. The study will examine Mumbai's 149-kilometre coastline, changes in land use and climate patterns and the population living in vulnerable coastal stretches. It is understandable that the BMC wants updated information because Mumbai's physical landscape has changed substantially. The Coastal Road, reclamation and other developments have altered parts of the coastline, while salt-pan areas on the eastern side have also come under development pressure.

But there is an obvious question. Is Mumbai studying the problem again when it should already be acting on what it knows?

A fresh vulnerability assessment is useful, even essential. But a study should not become a substitute for action. Mumbai has had repeated warnings for years. It has experienced catastrophic flooding before. It knows that high tide combined with intense rainfall can overwhelm its drainage system. It knows that mangroves, wetlands, floodplains and other natural buffers are valuable. It knows that reclamation and indiscriminate concretisation can alter drainage patterns. What it now needs is not merely another map showing where the water might go. It needs a clear implementation strategy showing what must be done before the water gets there.

The most vulnerable areas are not necessarily those closest to the sea alone. They are low-lying areas where the sea, stormwater and inadequate drainage can interact.

South Mumbai is an obvious danger zone. Cuffe Parade, Nariman Point, Mantralaya, Colaba, parts of Marine Drive, Girgaon, Breach Candy, Haji Ali and Worli have repeatedly figured in assessments and warnings. A 2023 RMSI analysis identified several vulnerable locations, including areas around the Mithi River, parts of Colaba, Haji Ali, coastal stretches of Worli and settlements around Mahim Fort. It also identified risks around the airport and the Jawaharlal Nehru Port Trust area.

The vulnerability extends well beyond the postcard image of South Mumbai. Much of Mumbai's core and parts of its suburbs stand on reclaimed or very low-lying land. Research has pointed to the Bandra Kurla Complex, the airport and Worli as examples of major built-up areas located on reclaimed land and therefore exposed to high tides and storm surges. Dharavi too is particularly vulnerable because of its low-lying location and its proximity to the Mithi River and drainage channels.

The western coastal belt and the creek systems on the eastern side deserve equal attention. Low-lying areas around Malvani, Bhayander and the western suburbs have been identified as particularly susceptible to tidal flooding, while the Mithi, Mahim and other waterways can become conduits through which tidal water moves inland. The eastern suburbs face their own vulnerabilities around creeks, salt pans and low-lying terrain.

This is why the phrase "Mumbai will be submerged" can be misleading. Mumbai is not one uniform geographical entity. Its elevation varies, its coastline is irregular and its drainage systems are different from one locality to another. One neighbourhood may face regular tidal flooding while another may remain relatively safe. Some areas may experience temporary inundation during extreme events decades before they face any possibility of permanent inundation.

The year 2050 has acquired an almost ominous significance in discussions about Mumbai. But 2050 should be understood as a planning horizon, not a date stamped on a calendar when the sea is expected to arrive.

Climate models work with scenarios. Their projections depend on future emissions, ocean behaviour, ice-sheet dynamics, land movement and local geography. They therefore cannot tell us that a particular building will be underwater on a particular date. What they can tell us is that the probability and severity of coastal flooding will increase as sea levels rise.

The scientific evidence is already strong enough to act on. A 2025 study of major Indian coastal cities found Mumbai and Kolkata among the cities facing the highest future coastal flooding risks, particularly under higher-emissions scenarios. The study's modelling also showed that lower-emissions scenarios reduce, but do not eliminate, the threat.

There is consequently no justification for waiting until the threat becomes visually dramatic. By the time the sea regularly reaches homes, roads and electrical installations, adaptation will be considerably more expensive.

If Mumbai is a city built intimately around the Arabian Sea, Kolkata's vulnerability is inseparable from the Hooghly, the Bay of Bengal and the wider Ganga delta system.

The UN has placed Mumbai and Kolkata in the same category of concern, but their physical vulnerabilities are not identical. Kolkata is a low-lying delta city and is affected not only by rising sea levels but also by land subsidence, river flooding, storm surges and the loss of wetlands that historically absorbed excess water.

Research using satellite observations has found significant land subsidence in parts of Kolkata. Between 2003 and 2011, parts of eastern Kolkata experienced subsidence of roughly 4 to 12 mm a year, while newer subsidence zones emerged west of the Hooghly between 2017 and 2021. Excessive groundwater extraction is one of the factors associated with this sinking.

That makes the arithmetic particularly worrying. If the sea rises while the land sinks, the effective rise relative to the ground can be greater than the rise of the sea alone.

Kolkata's eastern and south-eastern fringes are particularly important because of their relationship with the East Kolkata Wetlands. Recent research has found that the wetlands have shrunk dramatically over the past three decades, while another study of flooding between 2016 and 2023 found south-eastern Kolkata, including the East Kolkata Wetlands and adjacent rapidly urbanising areas, to have the highest flood hazard. The study also concluded that land-use change and wetland loss can have a stronger influence on flood levels than elevation alone.

Kolkata's vulnerability is therefore also a story about what happens when a city gradually destroys the very ecological systems that once protected it.

It would be tempting to blame everything on global warming and leave it there. That would be convenient, but incomplete.

Climate change is the great multiplier. It raises the baseline sea level, warms the oceans and can intensify extreme weather. But cities determine how badly those changes affect their populations.

Mumbai's concretisation has reduced natural spaces through which water can be absorbed. Wetlands and mangroves have been degraded. Drainage channels have been narrowed or encroached upon. Reclamation has altered the relationship between land and sea. Kolkata has experienced wetland loss, urban expansion and groundwater-related subsidence.

The UN itself emphasises that sea-level rise is not simply an environmental problem. It threatens housing, drinking water, sanitation, health, infrastructure, livelihoods and economic stability.

The poorer sections of the population are likely to suffer first and most severely. A wealthy household may be able to move to a higher floor, reinforce a building, insure property or eventually relocate. A fishing community, slum dweller, street vendor or low-income household living close to a creek has considerably fewer options.

That is why the issue should not be reduced to a debate about whether Mumbai's luxury towers will be submerged. The real question is whether the city's poorest and most vulnerable citizens will be repeatedly displaced by floods long before the city's skyline is visibly threatened.

The first requirement is to stop treating climate adaptation as an occasional project. It has to become part of every major urban decision.

Mumbai needs a detailed ward-by-ward coastal risk map that is continuously updated rather than produced once every few years. The map must combine sea-level projections with tides, rainfall, storm surges, drainage capacity, land subsidence, land elevation and population vulnerability. Every major infrastructure project should then be tested against those projections.

The second requirement is to protect natural defences. Mangroves, wetlands, mudflats, salt pans and floodplains are not vacant land waiting to be developed. They are part of Mumbai's flood-control infrastructure. The same principle applies to Kolkata's East Kolkata Wetlands and the wider deltaic ecosystem.

Third, drainage must be treated as climate infrastructure rather than merely municipal housekeeping. Drains, pumping stations, stormwater channels and outfalls have to be designed for the rainfall and tidal conditions that cities are likely to experience in the future, not those they experienced decades ago.

Fourth, development permissions in vulnerable areas need to become much more stringent. It makes little sense for one arm of government to warn that a locality is at risk from inundation while another arm continues to encourage intensive construction there without adequate adaptation measures.

Mumbai also needs to ask whether every piece of coastal reclamation is compatible with the city's long-term survival. Infrastructure that solves a transport problem today but increases flood vulnerability tomorrow cannot be called successful development.

Kolkata faces an equally urgent task of protecting wetlands, regulating groundwater extraction, restoring drainage channels and ensuring that urban expansion does not eliminate the natural spaces that absorb floodwater.

The responsibility cannot be pushed entirely on to the BMC or the Kolkata Municipal Corporation. Municipal bodies are the first line of defence, but they do not control everything that determines coastal vulnerability.

The Maharashtra and West Bengal governments have crucial responsibilities in land-use regulation, coastal management, infrastructure and disaster preparedness. The Union government has a role in climate finance, scientific monitoring, coastal regulation and long-term adaptation policy. Metropolitan development authorities, ports, infrastructure agencies and planning bodies must also be brought into one integrated framework.

And there is a larger responsibility that belongs to all levels of government. Climate warnings cannot be treated as news events that generate anxiety for a few days and disappear from public discussion.

The BMC's new study should therefore not end as another report on a shelf. It should become the basis for a legally backed coastal resilience programme, with deadlines, funding, accountability and public disclosure. Kolkata needs an equivalent seriousness.

The UN warning should not frighten Mumbai and Kolkata into paralysis. It should frighten them out of complacency.

Neither city is going to vanish beneath the sea tomorrow. Nor does the UN report say that. What it says is considerably more important: sea-level rise is already happening, it is accelerating, and cities such as Mumbai and Kolkata are particularly exposed because geography, urbanisation and land subsidence magnify the consequences.

The rest of India's coastline faces varying degrees of risk too. Chennai, Kochi, Surat, Visakhapatnam, Mangaluru and other coastal cities are exposed to combinations of sea-level rise, storm surges, erosion and extreme rainfall. A recent comparative study of Indian coastal cities found Mumbai and Kolkata among the highest-risk cities, although the nature and intensity of vulnerability differ from place to place.

For Mumbai and Kolkata, however, the warning has a special resonance. Both cities have already received versions of it before. Mumbai has had its climate action plan. Kolkata has had studies on flooding, subsidence and wetlands. Scientists have repeatedly explained the danger. The evidence has accumulated.

What is required now is to move from prediction to preparation. The sea does not negotiate with municipal boundaries, political terms or development timetables. It advances in millimetres, almost imperceptibly, while cities advance in concrete and steel. The tragedy would not be that Mumbai and Kolkata were warned too late. The greater tragedy would be that they were warned early enough and still chose to wait.