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This monsoon season has been unusually severe for the Western Himalayan region, which has witnessed extreme weather events almost daily. Relentless, intense rainfall and repeated cloudbursts have triggered flash floods, landslides and mudflows, wiping out villages, claiming hundreds of lives, cutting off highways and bringing life to a standstill. To understand whether the Himalayas have reached a point from which it may be extremely difficult to recover, Down To Earth speaks with Anil Kulkarni, distinguished scientist at the Indian Institute of Science, Bengaluru; S P Sati, head, department of basic and social science, College of Forestry, Ranichauri, Tehri Garhwal; Kieran Hunt, climate scientist, University of Reading, UK; and Swapnamita C Vaideswaran, scientist, Wadia Institute of Himalayan Geology, Dehradun.
ANIL KULKARNI
DISTINGUISHED SCIENTIST AT INDIAN INSTITUTE OF SCIENCE, BENGALURU
The cryosphere, comprising glaciers and glaciated terrain where much of the water exists as ice, has undergone dramatic changes over the last 40 years, especially since the 1980s. Nowhere is this more evident than in the Himalayas, where warming is accelerating faster than the global average. While global temperatures have risen by about 1.5°C since the onset of industrialisation, in the Indian Himalayas, the increase is closer to 2°C.
Interestingly, precipitation levels over the Himalayas have not changed significantly over the past 30-40 years, but there has been a marked shift in the form of precipitation. Snowfall has decreased, while rainfall has increased. This change poses two major challenges: rising temperatures and declining snowfall—both contributing significantly to the retreat of Himalayan glaciers. What does this mean for us?
As glaciers retreat, they leave behind moraines—loose aggregates of sand, soil, boulders and large rocks transported by the glaciers. These moraine-covered areas are highly prone to landslides. Additionally, glaciers, as they advance, tend to carve depressions in the terrain that are filled with meltwater, instead of ice, and form glacial lakes. These lakes, if breached, can lead to sudden and potentially catastrophic floods known as glacial lake outburst floods (GLOFs). Over the past 30-40 years, the number of such glacial lakes in the Himalayas has risen sharply. While not all of them caused flash floods, they are potential sources of future disasters.
A third concern is the formation of hanging glaciers. On steep slopes, typically those with gradients exceeding 30 degrees, the base of the glacier remains firmly anchored to the underlying rock due to frosty conditions. But as temperatures rise and the ice begins to melt, meltwater seeps down to the contact point between the ice and the rock, weakening the bond and leading to glacier slippage and potential flash floods.
Take the Dharali disaster of August 5, where intense rainfall triggered a debris-laden flash flood. Satellite images showed significant glacier retreat and moraine formation upstream. It is likely that a landslide created a temporary waterbody that, if it continues to grow, could breach the moraine and cause another flood. Furthermore, the region is dotted with hanging glaciers, heightening future risks.
Although we need comprehensive investigations to fully understand how such disasters occur, especially given the unpredictability of rainfall, my concern is that Himalayan glaciers may be approaching a point of no return. Our models suggest that in the central Himalayas, Himachal Pradesh and the Kashmir Valley, 80-90 per cent of glaciers could disap-pear by the end of this century. Even if we succeed in reducing global temperatures in the future, it is uncertain if these glaciers can recover.
The implications are stark. With increased heavy rainfall and cloudbursts, we can expect more flash floods, glacial lakes and mudflows, such as the one in Dharali. It will be dangerous for communities living in the high-altitude regions.
(As told to Rohini Krishnamurthy)
S P SATI
HEAD, DEPARTMENT OF BASIC AND SOCIAL SCIENCE, COLLEGE OF FORESTRY, RANICHAURI, TEHRI GARHWAL (VEER CHAN-DRA SINGH GARHWALI UTTARAKHAND UNIVERSITY OF HORTICULTURE AND FOR-ESTRY, BHARSAR)
Every component of the Himalayas, be it glaciers, rainfall or vegetation, has its own critical tipping point, and many of these thresholds are now dangerously close. Based on the scale of destruction this year, I believe that the level of precipitation in the Himalayas has nearly reached such a tipping point.
Consider the data: in August, the Western Himalayas received 140 per cent more rainfall than normal, and the overall monsoon season saw an excess of around 120 per cent. The impact was catastrophic. If rainfall had reached 150 per cent above normal, entire valleys may have been submerged.
This year’s devastation resulted from a rare convergence of monsoon and western disturbances. Over the past 20 years, these combined events have doubled in frequency and are becoming increasingly erratic. Trans-Himalayan regions like Ladakh and Zanskar, which historically received little rainfall, are now experiencing abnormal precipitation.
The effects of such extreme weather vary based on elevation, slope, rock type and soil conditions. For example, the mountains in front of Pipalkoti (Uttarakhand) are solid rock with minimal soil—so landslides are rare despite heavy rainfall. In contrast, Zanskar (Ladakh) is composed of loose debris, where even 50 mm of rainfall in 24 hours can trigger deadly landslides.
Timing is also critical. Early-season rain mostly affects the surface layer. But by August or September, when the soil is fully saturated, even light rain can lead to large-scale landslides. This was the main cause of the Dharali and Chishoti tragedies this year.
The Intergovernmental Panel on Climate Change’s 2007 report warned of such impacts emerging by 2030 or 2050. But what we are seeing now suggests these effects are arriving much earlier than predicted.
(As told to Raju Sajwan)
KIERAN HUNT
CLIMATE SCIENTIST, UNIVERSITY OF READING, UK
Western disturbances at the beginning of the monsoon are becoming more frequent because the subtropical westerly jet stream is south for far longer, and is not migrating northwards in a seasonal cycle until later on. But it is also true that we are in September now, so there is not much of the subtropical westerly jet stream in sight anymore. Therefore, these disturbances could be Potential Vorticity (PV) cut off lows—formed around the Polar regions, in the upper levels where the jet stream also exists. Here, there is a region of high PV, parts of which can detach and migrate to lower latitudes. When they do, it results in these deep upper-level low-pressure troughs. Their shape looks similar to western disturbances.
Historically, there has not been much of a trend in the total number of western disturbances. When you separate them by months, you can see that there is a trend in April, May and June, which is because of the subtropical westerly jet stream. But this trend does not explain the western disturbances deeper in the monsoon.
There are other important aspects of PV cut-off lows as well. They move more slowly and so dump more precipitation, they are often stronger as well and are hence associated with deeper convection and stronger winds—and consequently, longer lasting impacts. During the monsoon, they could cause more damage.
There is also an east-west dipole in the trend of monsoon rainfall, where the east is getting less rainfall and the west is getting more. But that does not really affect the northern Indian states. I believe you need some upper-level activity like an upper-level trough in the western Himalayan region apart from the monsoon break period to be able to cause rainfall in this region. This is necessary to bring the monsoonal air into the region. The monsoon cannot easily do this on its own.
For these very extreme events that we have observed throughout the current monsoon season, the explanation is better framed as changes to the upper-level activity and the western disturbances than to the changes in the monsoon. To get monsoonal moisture to the mountains you need the upper-level configuration to be correct. We need to be looking at the changes in the upper -level configurations and changes to the two flavours of western disturbances.
We can say with reasonable certainty that a delayed retreat of the sub-tropical westerly jet stream at the beginning of the monsoon, due to which the western disturbances stay longer and affect India, is connected to climate change—and not to the inter-decadal variability that comes from phenomena like the North Atlantic Oscillation or the El Niño-Southern Oscillation.
We can link the change in the sub- tropical westerly jet stream with the differential heating over the Tibetan Plateau. The subtropical jet stream itself is a response to the thermal gradient in the upper atmosphere. It is kind of a balancing wind that keeps the thermal gradient in the upper atmosphere. Global warming has heated up the Tibetan Plateau more than the surrounding regions. This warming changes the configuration, the gradient in the temperature and changes the character of the subtropical jet stream.
If we are able to somehow cool back the Earth again, we may be able to return to the return to the regular seasonal migration we saw in the 20th century, when the subtropical jet stream moved northward and southward year after year in a periodic manner. The change in the jet stream is not irreversible, but appears to be because of climate change. If we can remove the impacts of cli-mate change, we would go back to the configuration as it was earlier.
(As told to Akshit Sangomla)
SWAPNAMITA C VAIDESWARAN
SCIENTIST D, WADIA INSTITUTE OF HIMALAYAN GEOLOGY, DEHRADUN
The Himalayas is defined as much by its geology as by its climate. While the Earth's geological systems are resilient and may not yet be at a tipping point, we are certainly seeing unmistakable warning signs of climate change. Take Uttarakhand, a transitional zone along the Himalayan arc, influenced by both Indian summer monsoon and western disturbances. Here, the influence of western disturbances is typically confined to the winter months. This year, the western disturbances persisted well beyond April, appearing multiple times—a clear signal of warming climate.
In Dharali, we saw an orographic rainfall event at elevations above 4,000 metres; instead of snow, the higher-altitude regions received torrential rainfall—something entirely unexpected. Though in the valley in Harsil, which sits at 2,500 metres above sea level, there was very less rain. Some initially speculated that a glacial collapse or avalanche had occurred. But our observations confirmed otherwise—it was simply an unprecedented volume of rainfall. This excess water flowed into the Khir Ganga, causing flash floods and landslides along the channel.
A similar situation unfolded in Nanda Nagar of Chamoli district, where cracks appeared in the ground—much like the land subsidence that Joshimath town in Chamoli has been experiencing for the past few years. The underlying issue appears to be excessive rainfall saturating the ground, leading to land instability.
We have analysed 100 years of climate data and the trends are clear: temperatures are rising, overall rainfall is decreasing, but when it does rain, it happens in extreme bursts. These are classic indicators of climate change. What concerns me most is that these extreme weather events have become more common, especially in the last decade, and we do not yet know what future patterns will look like. Will this become an annual occurrence? We urgently need to monitor and prepare.
But we must also acknowledge the role of human interference. The Himalayas is seismo-tectonically active. The tectonic processes influence climate, and in turn, climate reshapes the landforms and topography. This interplay is why we are now witnessing an increase in disasters like landslides. We are also contributing to instability through deforestation and land-use change. For example, in Dharali, apple orchards have replaced deodar forests, disrupting the local ecosystem and microclimate.
While highways often draw criticism, roads built under the Prime Minister Gram Sadak Yojana are frequently overlooked. Road plans need surveys from geologists and technical planning. planning. Lack of the use of a good-resolution topographic map inhibits proper alignments in mountain terrain, and often causes instability. This happens because we overlook the water channels. We are now cutting directly into slopes, creating what is known as cut-slope topography. When you undercut to make way for a road, the entire hillside is prone to collapse. In that case, understanding the litho-structural units is of prime importance. The role of a geologist in any mountain development project is therefore required the most. We also cannot do without hydropower projects. Hydropower is so far the cleanest form of energy. What is more required is that projects complete on time, for minimising environmental concerns.
Looking ahead, I fear greater risks. Springs are drying, glaciers are melting and rainfall is intensifying. Intense surface flows cause destructive erosions. Yet none of this is recharging groundwater. The water is just running off. The consequence? A future freshwater crisis. A drought led to collapse of the Indus Valley Civilisation. We may be heading towards a similar situation. The warnings are all around us.
(As told to Dakshiani Palicha)
This article was originally published in the September 16-30, 2025 print edition of Down To Earth