Mumbai Climate Change Rainfall: Mumbai’s recent deluge reflects a changing monsoon shaped by climate change as much as El Niño. Experts say warming oceans and a hotter atmosphere are driving fewer rainy days but far more intense downpours, exposing the city’s ageing drainage systems and growing vulnerability to urban flooding.

For most of June, the story of India’s monsoon was one of delay and deficit. A strengthening El Niño in the Pacific was pushing the Southwest Monsoon back, and by the end of the month the country was staring at a 40 percent rainfall shortfall. Then, within days, the sky flipped. As the monsoon shifted into an active phase, Mumbai and the rest of India’s west coast were hit by rain so intense that the national deficit collapsed from 40 percent to 20 percent in less than a week, as of July 6.

The whiplash has revived a debate among climate scientists that goes beyond this one season: it is no longer only about how much rain a city gets, but how that rain arrives.

A new briefing from Climate Trends lays out the case that a warmer atmosphere and rapidly heating oceans are loading the air with more moisture than before, which means fewer rainy days overall but far more violent bursts when the rain does come. El Niño, in this reading, still controls the timing and broad strength of the monsoon — but climate change is increasingly writing its character, turning downpours shorter, sharper, and more likely to overwhelm drains built for a gentler era.

Mumbai Climate Change Rainfall Intensifies Monsoon Extremes

Mumbai’s own numbers make the point. In the first seven days of July alone, the city saw four separate spells of triple-digit rainfall. The Colaba observatory logged 791 mm between July 1 and 7 — more than its entire climatological average for the whole month of 768.5 mm. Santa Cruz recorded 879 mm in the same window, brushing up against its monthly normal of 919.9 mm.

Mahesh Palawat, Vice President of Meteorology and Climate Change at Skymet Weather, pointed to a pile-up of weather systems as the immediate trigger. “Monsoon is presently in an active phase, with several weather systems prevailing across the country,” he said, noting a depression over Odisha and a cyclonic circulation over Maharashtra keeping both arms of the monsoon active, while continuous moisture from the Arabian Sea kept regenerating cloud cover over the state.

Dr Raghu Murtugudde, Emeritus Professor at the University of Maryland and a retired professor at IIT-Bombay, went further, arguing that the two forces driving this monsoon can no longer be pulled apart. “El Niño just cannot be separated from global warming anymore,” he said, describing how both the Arabian Sea and the Bay of Bengal were firing at once, feeding moisture into the core monsoon zone that eventually rides the Western Ghats and dumps over Mumbai.

Rewriting the Monsoon’s Rulebook

Palawat said the shift is structural, not a one-off. Weather systems that form in the Bay of Bengal, he explained, have started tracking west instead of northwest, while the Arabian Sea’s record warming has added extra moisture to the mix, keeping clouds regenerating for days on end wherever a weather system parks itself.

Dr K J Ramesh, former Director General of the India Meteorological Department, framed it as a break from the monsoon India used to know. “We know that the character of the monsoon has changed forever due to global warming,” he said. “Rains will be in the form of short duration and high intensity, whether there is an El Niño or no El Niño.” He pointed to Rajasthan, Gujarat and West Madhya Pradesh, where Western Disturbances alone can no longer explain the volume of rain now falling — an added moisture feed from the Arabian Sea, he said, has changed the pattern across the region.

Research cited in the briefing backs this up on a larger scale: the Middle East has been warming almost twice as fast as the rest of the inhabited world, and that heating has been linked to nearly half — 46 percent — of the intensified rainfall over Northwest India and Pakistan between 1979 and 2022, by pushing moisture northward out of the Arabian Sea.

The Long-term Drift

Zoom out from any single storm and the trend holds. Comparing 1981–2000 with 2001–2024, average monsoon rainfall has climbed by nearly 15 percent in Mumbai and 23 percent in Pune, according to data from the Council on Energy, Environment and Water (CEEW).

Looking ahead, a separate report — Indian Coastal Region: Climate Projections 2021–2040 — suggests suburban Mumbai and parts of coastal Maharashtra and Gujarat should expect almost an additional week of heavy rain during the Southwest Monsoon in the coming years, alongside a projected 18 percent rise in the region’s already-massive 1,749 mm monsoon baseline. The same projections point to rising temperatures across the board, including a 1.3°C increase in both summer wet-bulb and winter minimum temperatures.

When Rain meets a City That isn’t Ready

Climate change, though, is only half the story of why Mumbai floods. The briefing frames urban flooding as a climate-plus-exposure problem — extreme rainfall colliding with a city whose drains, floodplains and green cover haven’t kept pace.

Ramesh was blunt about what that means on the ground. “It is no longer a matter of warnings anymore as substantial warnings have been issued well in time. It is now a preparedness and response issue,” he said, calling for full desilting of drains ahead of every monsoon and blaming unchecked concretisation for leaving trees with no room for their roots to breathe.

Dr Vishwas Chitale, a Fellow at CEEW, described the immediate toll of the past week’s rain — an orange alert in Mumbai and a red alert in Pune, both signalling rainfall heavy enough to disrupt daily life. He pointed to early warning systems and structured flood-resilience plans, like the one CEEW helped develop with the Thane Municipal Corporation, as the kind of groundwork cities now need. “We need to come out with some practical solutions on the ground to be able to manage urban flooding better,” he said.

Aarti Khosla, Director of Climate Trends, put the challenge in starker terms: extreme rainfall is no longer a possibility to plan around but a near-certainty to plan for. “The question is no longer whether extreme rainfall events will occur, but whether our cities are prepared to withstand them,” she said, calling for climate-resilient drainage, nature-based flood defences and urban planning that treats risk as a starting assumption rather than an afterthought.

The briefing’s broader point is a simple one: urban flooding happens when saturated drainage meets any of several triggers — torrential rain, storm surge, sea-level rise, groundwater seepage, or simply a city with too little permeable ground left to absorb water. Global warming is intensifying the rainfall trigger, and dense, paved-over cities are amplifying what happens next.

As one line from the briefing puts it, cities designed for yesterday’s climate are struggling to cope with today’s extremes — and, if the projections hold, tomorrow’s will demand even more.

The biggest waste-related climate threat in Kerala isn’t the garbage piling up in bins or the plastic littering its streets. It’s the wastewater flowing out of millions of homes every day. The state’s latest Greenhouse Gas Inventory Report shows that domestic wastewater accounts for more than 96% of greenhouse gas emissions from Kerala’s waste sector, making it the state’s largest waste-related emitter.

According to the report, 96.14% of waste-sector greenhouse gas emissions in 2023 came from domestic wastewater. This includes wastewater generated from everyday household activities such as toilets, bathrooms, kitchens, laundry and cleaning. When the organic matter present in this wastewater breaks down in oxygen-poor conditions, it releases methane, a greenhouse gas far more effective at trapping heat in the atmosphere than carbon dioxide.

While domestic wastewater dominates the sector’s emissions, other sources contribute much less. Municipal solid waste disposal accounted for just 1.7%, while industrial wastewater contributed 2.16%. Together, Kerala’s waste sector emitted 1.92 million tonnes of carbon dioxide equivalent (MtCO₂e) in 2023.

The findings reveal a sharp contrast between Kerala’s visible waste challenges and the hidden sources driving climate emissions. While garbage remains the most noticeable part of the waste problem, wastewater has emerged as the state’s biggest climate concern within the sector.

Wastewater: The Emissions We Don’t See

Unlike overflowing garbage bins or plastic waste on roadsides, wastewater remains largely invisible once it leaves households. However, the systems used to manage this wastewater play a major role in determining how much methane is released.

According to the inventory, Kerala’s sanitation systems are still dominated by decentralised methods. Pit latrines account for 74.06% of sanitation systems, septic tanks account for 24.62%, while piped sewer systems make up only 0.26%.

Individually, a single septic tank or pit latrine may appear insignificant. But across millions of households, these systems collectively become the largest source of waste-sector greenhouse gas emissions.

The report highlights that improving sanitation infrastructure is not only a public health priority but also an important climate action measure. Better wastewater treatment can reduce methane emissions while improving water quality and sanitation outcomes.

Why Waste Reforms Haven’t Reduced Emissions

Over the past decade, Kerala has invested significantly in improving solid waste management. Programmes focused on source segregation, composting, waste collection and initiatives such as Haritha Karma Sena have helped reduce open dumping and improve municipal waste handling.

However, these improvements have not translated into a major decline in waste-sector greenhouse gas emissions. The report estimates that emissions from the sector were 1.94 MtCO₂e in 2005 and 1.92 MtCO₂e in 2023, showing only a marginal reduction over nearly two decades.

The reason is that Kerala’s waste management progress has mainly focused on solid waste, while wastewater systems continue to generate methane emissions on a daily basis. The findings suggest that reducing garbage alone will not be enough to achieve significant emission reductions.

Why Solid Waste Still Matters

Although municipal solid waste contributes a relatively small share of current emissions, it remains an important part of Kerala’s waste challenge. The report notes that, based on Kerala State Pollution Control Board data, the inventory assumes that no municipal solid waste has been disposed of in dumpsites since 2017.

However, old dumpsites continue to release methane because organic waste buried decades ago can keep decomposing for years. This means some of today’s emissions are linked to past disposal practices, while domestic wastewater continues to create new emissions every day.

Together, these factors explain why Kerala’s overall waste-sector emissions have remained largely unchanged despite improvements in solid waste management.

A New Focus for Kerala’s Climate Action

The inventory points to a shift in how Kerala approaches waste and climate action. Efforts to collect, segregate and process solid waste remain essential for reducing pollution and protecting public health. But the state’s emissions data show that wastewater management must become a larger part of the climate conversation.

Expanding sewage treatment networks, improving septage management and strengthening sanitation infrastructure could play a crucial role in reducing emissions from the sector.

Kerala’s waste story has long been shaped by measures to reduce plastic waste, garbage collection and dumping. But, addressing wastewater will be key to achieving meaningful reductions in the state’s waste-sector greenhouse gas emissions.

Mumbai rain alert remains in place as the India Meteorological Department (IMD) forecasts continued heavy rainfall across the city and the Konkan region until July 7, warning that intense showers could trigger urban flooding, transport disruptions, landslides and rough sea conditions over the coming days.

The IMD’s Regional Meteorological Centre (RMC), Mumbai, said widespread rainfall with heavy to very heavy rainfall at several places and extremely heavy rainfall at isolated locations is likely over Konkan and the adjoining ghat areas of Madhya Maharashtra between July 3 and July 7. The weather department attributed the active monsoon spell to the combined influence of an offshore trough extending from the Maharashtra to Karnataka coast, a low-pressure area over the northwest Bay of Bengal that is expected to intensify, and a shear zone across central India.

The warning comes after several days of relentless rain across Mumbai, which has inundated roads, slowed suburban train services, disrupted flights and left authorities scrambling to minimise the impact of the monsoon on one of India’s busiest metropolitan regions.

IMD issued a Red Alert for Mumbai, Mumbai Suburban, Thane, Palghar and Raigad, indicating the likelihood of extremely heavy rainfall at isolated places. The alert also warned of strong winds, rough sea conditions and the possibility of flooding in low-lying areas, especially during periods of high tide. According to the weather department, the prevailing weather systems are expected to keep moisture supply active over western Maharashtra, sustaining intense rainfall over the region.

The heavy rainfall has already taken a toll on transport infrastructure. Waterlogging was reported from several parts of Mumbai, slowing road traffic and disrupting the city’s suburban railway network, the lifeline for millions of commuters. Flight operations at Mumbai’s Chhatrapati Shivaji Maharaj International Airport were also affected by poor visibility and adverse weather. On July 5, runway operations were briefly suspended before services resumed as conditions improved. Landslides and falling debris also affected rail connectivity on sections of the Mumbai–Pune corridor, highlighting the broader impact of the ongoing monsoon spell.

Mumbai Rain Alert: Flooding and Transport Disruptions Continue

Rainfall totals have underscored the intensity of this year’s monsoon. According to media reports citing weather data, some parts of Mumbai received over 300 mm of rainfall within 24 hours, while the city crossed 1,000 mm of cumulative rainfall during the first 12 days of the southwest monsoon, far above what is normally recorded during the period. Such intense rainfall has repeatedly overwhelmed the city’s drainage network, leading to waterlogging in several neighborhoods and traffic congestion across major roads.

As a precautionary measure, the Brihanmumbai Municipal Corporation (BMC) declared a holiday today, for schools, colleges and government offices. The University of Mumbai also postponed examinations scheduled for the day. Civic authorities urged residents to avoid unnecessary travel and remain indoors unless essential, while disaster response teams were deployed in vulnerable locations across the city.

The IMD has warned that the current weather conditions could result in flash floods, localized inundation in urban and low-lying areas, riverine flooding in some catchments, landslides in vulnerable hilly regions and damage to weak structures. It also cautioned that essential civic services, including water and electricity supply, may face temporary disruptions, while road, rail, air and ferry transport could continue to be affected if heavy rainfall persists.

The weather department has advised residents to avoid waterlogged roads, stay away from landslide-prone slopes and refrain from taking shelter under trees during thunderstorms because of the risk of lightning. Authorities managing dams, barrages and hydroelectric projects have also been asked to take precautionary measures in anticipation of heavy inflows.

Along the coast, the IMD has issued a warning for fishermen, advising them not to venture into the sea off the North Maharashtra and South Maharashtra–Goa coasts until July 7. Strong winds of up to 65 kmph are expected at sea. The IMD has advised ports along the Maharashtra coast to raise a caution signal. With multiple weather systems continuing to influence conditions over western India, authorities have urged residents to closely monitor official weather bulletins as the active monsoon spell is expected to continue through the week.