The atmospheric systems that bring winter rain and snow to the Himalayas are changing in ways that complicate a familiar assumption that more weather systems mean more precipitation.

A study published in the International Journal of Climatology in March 2026 examined winter precipitation across the Western Himalayan region over two 30-year periods, 1961–1990 and 1993–2022. Using ERA5 atmospheric reanalysis data, the researchers found that Western Disturbances and the number of days associated with them had increased, while the density of their tracks across the study region had declined as their paths shifted northward.

The study also identified a decline in large-scale precipitation. A greater proportion of the precipitation that did occur fell as rain rather than snow, partly offsetting the reduction in snowfall. These findings point to changes in the location, form and mechanisms of precipitation, rather than a uniform increase in rainfall across the Himalayas.

What are Western Disturbances?

Western Disturbances are eastward-moving weather systems that originate in the Mediterranean and adjoining regions and travel towards South Asia. They are embedded in the westerly flow of the middle and upper atmosphere and are an important source of winter precipitation over northwestern India and the western Himalayas.

When these systems reach the mountains, their effects depend on several interacting factors: the amount of moisture they carry, the strength and direction of atmospheric winds, the temperature profile of the air and the shape and elevation of the terrain.

As moist air rises over mountain slopes, it cools and water vapour condenses into cloud droplets or ice crystals. Depending on atmospheric conditions, precipitation can fall as rain or snow. The distribution of precipitation varies with the system’s track and intensity, as well as local topography. A shift in the path of a Western Disturbance can therefore change which valleys and mountain slopes receive precipitation, even if the overall number of systems increases.

Why Frequency Alone Does Not Explain the Rainfall

The 2026 study highlights an important distinction between the occurrence of Western Disturbances and the precipitation they produce. Although the researchers found an increase in the number of disturbances and associated days, their analysis showed that fewer tracks passed through the Western Himalayan study region. The northward shift was associated with a decline in large-scale precipitation.

The study also found that rising temperatures increased the atmosphere’s capacity to hold moisture, while weaker vertical winds reduced the upward movement of air. Reduced transport of moisture into the upper troposphere also affected cloud microphysical processes that support large-scale precipitation.

These processes help explain why a warmer atmosphere does not automatically translate into greater precipitation everywhere. Temperature, moisture availability, vertical air movement and the location of weather systems all influence how much precipitation forms and where it falls.

The findings also have implications for snowfall. When temperatures rise, a larger share of precipitation can fall as rain instead of snow, depending on conditions within the atmosphere and near the surface. Such a change can affect seasonal snow accumulation and the timing of water entering Himalayan river systems.

How Does Climate Change Fit Into the Picture?

Climate change alters the background conditions in which Western Disturbances develop and travel. Rising temperatures influence atmospheric moisture, while changes in circulation can affect the systems’ tracks and the way they interact with mountain terrain.

However, researchers have identified different trends across different parts of the wider Himalayan region. Findings from the Western Himalayas cannot automatically be applied to Nepal or the eastern Himalayas, where the influence of weather systems, topography and moisture sources may differ.

The October 11, 2026, flash flood in Nepal’s Budhi Gandaki river system illustrates why this distinction matters. According to the International Centre for Integrated Mountain Development (ICIMOD), a preliminary assessment suggested that a landslide may have blocked the river before the temporary barrier failed, releasing water, sediment and debris downstream. The organisation said further investigation was needed to establish the event’s precise trigger.

The flood, therefore, cannot be attributed to a change in Western Disturbances on the available evidence. The scientific questions surrounding the event include the mechanics of the landslide, the temporary river blockage and the release of the accumulated water. Establishing whether weather conditions contributed to the initial slope failure requires separate evidence.

What Scientists Need to Examine Next

Understanding changes in Himalayan precipitation requires researchers to look beyond the number of Western Disturbances recorded in a season. Their tracks, intensity, moisture transport, vertical wind patterns and the proportion of rain and snow all need to be examined together.

Long-term observations and atmospheric reanalysis can help identify regional trends, while measurements of snow cover, precipitation and mountain hydrology can show how those changes affect water availability. Comparisons across the western, central and eastern Himalayas are also necessary to establish where trends are consistent and where they differ.

The central finding is that changes in atmospheric circulation can redistribute precipitation even as the climate warms. For the Himalayas, where snow accumulation, river flow and mountain ecosystems depend on the timing and form of precipitation, understanding these regional differences is essential to explaining how the water cycle is changing.

The torrential rainfall that flooded Istanbul on October 14–15 has highlighted a growing challenge for cities confronting extreme weather: how to prepare for heavier rainfall when the extent of climate change’s influence varies across regions, and the damage depends partly on how urban landscapes are built.

A new analysis by the ClimaMeter research team finds that weather patterns similar to those behind the floods now bring about 7% heavier rainfall and 9% stronger winds than comparable patterns recorded between 1950 and 1987. Temperatures in the region of heaviest rainfall are up to 1.5°C higher than in the historical comparison period.

However, the increase in rainfall was not statistically significant over Istanbul itself. The researchers identified significant rainfall increases across parts of western and north-western Anatolia and along the Black Sea coast north of the city, while natural climate variability also contributed to the event.

The floods triggered 1,277 flooding incidents and 15 landslides across Istanbul, according to the analysis. ClimaMeter reported 194 millimetres of rainfall at Ömerli in the Beykoz district, while Istanbul’s disaster coordination centre, AKOM, reported 277.1 millimetres in Beykoz during the event. Two people died, 595 people were evacuated after becoming trapped, and roads and schools were affected.

The findings underline an important distinction: climate change can alter the conditions associated with extreme rainfall, but it does not explain every aspect of an individual flood. Urban drainage, land use and exposure determine how rainfall translates into damage.

What climate attribution reveals

The ClimaMeter analysis compared the atmospheric conditions of October 14–15, 2026, with similar weather patterns from 1950–1987 and 1988–2025. Using the European Centre for Medium-Range Weather Forecasts’ ERA5 reanalysis data, researchers examined changes in precipitation, temperature and wind.

They estimated that about 3% of the rain-linked damage associated with the event was attributable to human-driven climate change, with an estimated range of 1–4%. This is a rainfall-based attribution estimate, not a calculation of the proportion of all damage caused by global warming. The methodology does not account for drainage capacity, impermeable surfaces or construction along streambeds.

The physical basis for heavier rainfall is well established. The Intergovernmental Panel on Climate Change (IPCC) explains that the atmosphere can hold approximately 7% more water vapour for every 1°C of warming. When atmospheric conditions are favourable, additional moisture can contribute to more intense precipitation.

The IPCC’s Sixth Assessment Report concludes that heavy precipitation has become more frequent and intense across most land regions with sufficient observational coverage, primarily because of human influence. Regional trends, however, are not uniform, and Mediterranean precipitation patterns are affected by considerable natural variability.

The Istanbul findings therefore point to a need for preparedness without overstating the evidence. The absence of a statistically significant local rainfall trend does not mean the city faces no climate risk. It means that the specific analysis did not establish a significant rainfall increase over Istanbul for the weather pattern examined.

Urban development can magnify flood damage

How a city responds to rainfall depends on more than the volume of water falling from the sky. Roads, buildings and other impermeable surfaces reduce the amount of water absorbed into the ground, increasing runoff. If drainage systems cannot carry away the additional water, streets and low-lying areas can flood rapidly.

Research conducted in Istanbul provides evidence of how planning decisions can influence this risk. A 2021 study by Seda Ertan and Rahmi Nurhan Çelik, published in Sustainability, modelled flood scenarios across a 1,653-hectare catchment of the Kağıthane Stream.

Representational image.image credit:Pexels

The researchers examined measures including green roofs, permeable road surfaces, rainwater collection and drainage channels. Their results indicated that green infrastructure could reduce surface runoff and peak flow rates, as well as the area inundated and the number of structures exposed to flood risk.

The findings suggest that flood management should extend beyond expanding conventional drainage infrastructure. Permeable surfaces can allow more rainwater to enter the ground, while green roofs and rainwater collection systems can help retain water before it reaches drainage networks. Their effectiveness nevertheless depends on local conditions and the intensity of rainfall.

A separate study published in the Journal of Flood Risk Management in January 2025 examined flood exposure and vulnerability in Istanbul’s Pendik district. The researchers found that flood-prone areas were associated with lower land values and greater concentrations of socially disadvantaged residents, including older people, refugees and people with lower levels of education.

The study identified substantial differences in vulnerability within the district. About 21% of the assessed Kaynarca basin fell into the study’s very-high-vulnerability category, while 20.4% was classified as high vulnerability. These classifications reflect the study’s specific assessment framework and should not be interpreted as estimates for Istanbul as a whole.

The research highlights an important dimension of urban resilience: communities do not experience flood risk equally. Housing conditions, access to resources, the location of residential areas and the ability to respond to warnings can influence how severely households are affected.

Building resilience beyond emergency response

The implications extend beyond Istanbul. Cities facing intense rainfall need to combine reliable drainage systems with land-use planning, early-warning mechanisms and protection of natural waterways.

Nature-based approaches can complement conventional flood defences. A 2024 review published in npj Urban Sustainability examined the role of nature-based solutions in flood-risk management, emphasising the importance of considering social and ecological outcomes alongside physical protection. Wetland restoration, urban green spaces and restored stream corridors can help retain water and reduce runoff, although they cannot eliminate the risk of flooding during extreme events.

For Istanbul, the findings also raise questions about development near waterways and the preservation of natural drainage routes. A recent report by the Turkish news agency Anadolu Agency, published on October 20, quoted Istanbul Technical University disaster-management researcher Ömer Ekmekcioğlu warning that heavily urbanised catchments and areas where natural drainage systems have been altered require particular attention.

The ClimaMeter team estimated that approximately 14.6 million people and US$558 billion in economic activity were exposed within the wider rainfall-hazard area. These figures represent exposure to the identified hazard, not the number of people directly affected or the economic losses incurred during the floods.

The broader lesson is that climate attribution and urban planning answer different but connected questions. Climate science helps establish how warming may change the intensity of weather hazards; urban-risk research examines why certain places and communities suffer greater consequences.

Istanbul’s floods demonstrate why both are necessary. Preparing for a changing climate requires understanding the rainfall, but reducing the damage also depends on where cities build, how they manage water and whether their infrastructure protects the people most exposed to risk.

Nepal estimates that recovering from the devastating August floods will cost at least $4.71 billion. The United Nations’ Fund for Responding to Loss and Damage has provisionally set aside 21.6 million dollars in response, an allocation that covers only a small portion of the country’s estimated climate damages fund requirements. This highlights the climate justice gap between the scale of losses vulnerable countries face and the international support available to rebuild.

The fund’s board approved the decision at an extraordinary meeting on October 22, 2026. Of the amount set aside, $20 million is intended for potential assistance to Nepal, while $1.6 million is earmarked for oversight costs. Nepal must still complete the funding request and project approval process before the money can be disbursed. The decision is the fund’s first country-specific emergency response. Its immediate value will depend on how quickly the proposed assistance can be converted into funding for recovery work.

Reconstruction Costs Put Pressure on Nepal’s Finances

The August floods affected communities along the Bhotekoshi–Trishuli river system and damaged infrastructure in the affected region. Nepal’s estimated recovery requirements include the costs of rebuilding damaged assets and restoring services disrupted by the disaster.

For the government, reconstruction creates demands beyond the immediate response. Roads, bridges and other public infrastructure need repairs, while affected households face the expense of restoring homes and livelihoods. These costs compete with existing public spending priorities, making external assistance important to the recovery effort.

The provisional $20 million allocation for Nepal is less than 0.5% of its estimated reconstruction requirements. The funding can contribute to selected needs, but the country will have to secure substantially more money to meet the overall bill.

Climate Damages Fund to Address Climate-related Losses

The Fund for Responding to Loss and Damage was established under the UN climate process at COP27 in 2022 and operationalised at COP28 in 2023. It was created to help vulnerable developing countries deal with the consequences of climate change that cannot be adequately addressed through adaptation alone.

These consequences include damage to infrastructure and livelihoods, as well as losses that are harder to value financially, such as harm to cultural heritage and ecosystems. The fund is intended to provide a dedicated channel for addressing such impacts. Nepal’s allocation puts that mandate into practice. However, a decision to reserve funds is only one stage in the process. The country must submit its proposal, and the relevant procedures must be completed before the allocation becomes money available for recovery projects.

The board has agreed to consider an exceptional route for Nepal’s request outside the fund’s regular application cycle. This could help avoid some of the delays associated with a standard funding round, although the actual disbursement timeline remains crucial.

International Demand Exceeds the Fund’s Resources

The funding gap is not unique to Nepal. According to figures reported in the October 2026 news report supplied for this article, the fund had received 176 requests from 119 countries, worth approximately $2.8 billion. Pledges amounted to around $822 million.

The disparity raises questions about the fund’s capacity to respond to multiple emergencies and other loss and damage needs. Even where a request qualifies for consideration, the resources available may not match the amount sought.

The Nepal decision also illustrates why the terms used in climate finance announcements matter. A pledge is a commitment to provide money; an allocation sets aside funds for a specified purpose; a disbursement means the money has actually been transferred. For communities awaiting assistance, the final stage is the one that enables work to begin.

What Happens Next?

Nepal’s recovery will require financing from several sources, as the UN fund’s allocation is far below the estimated reconstruction bill. The immediate task is to complete the procedures required to access the proposed funding and identify the projects it will support.

The fund will also need to demonstrate that its emergency process can deliver assistance without creating unnecessary delays. Its ability to mobilise additional contributions will determine how much support it can offer as requests accumulate.

Nepal’s case provides an early measure of the distance between the scale of climate-related damage and the financial resources currently available through this mechanism. The provisional allocation is a concrete step, but its contribution to recovery will become clear only when the money reaches the projects and communities for which it is intended.