Climate change played a key role in the “catastrophic” 2023 floods in the Himalayan state of Sikkim in India, a new study says.
The breach of one of the “largest, fastest-growing and most hazardous” glacial lakes in Sikkim, the South Lhonak lake, led to cascading floods that killed 55 people and washed away a 1,200 megawatt (MW) hydropower dam.
The event was identified as a glacial lake outburst flood (GLOF), which is a sudden release of water from a lake fed by glacial melt.
The research, published in Science, explores the many drivers of the GLOF, its extensive impacts and policy implications going forward.
“There are many, many factors that came together here,” the study’s lead author tells Carbon Brief, but the “main driver” was the destabilising effect caused by thawing permafrost.
The research also finds that the South Lhonak lake has been expanding for decades, due to meltwater from the glacier above, with its area growing 12-fold between 1975 and 2023.
The paper concludes that the GLOF highlights the “complex interactions” between climate change, glacier mass loss and human infrastructure in mountainous regions.
It also demonstrates the importance of “robust monitoring systems and proactive measures to minimise devastating consequences and enhance resilience”, the authors add.
Flood cascade
Sikkim is a small Himalayan state in north-east India, bordering China in the north, Bhutan in the east, Nepal in the west and the state of West Bengal in the south.
Part of the eastern Himalaya, Sikkim is host to more than 90 glaciers and Kanchenjunga, the world’s third-highest peak. Sikkim serves as the origin and upper river basin for the Teesta river, one of the largest tributaries of the Brahmaputra river system.
On the night of 3 October 2023, a ridge of frozen rock and other debris on the side of the South Lhonak glacier – called a “lateral moraine” – collapsed into the glacial lake. This set off a tsunami-like wave nearly 20 metres high that breached the front of the lake, sending 50m cubic metres of water – almost half the lake’s volume – downstream.
According to the study, the GLOF’s peak discharge “vastly exceeds” the magnitude of any meteorological flood in the region’s history, equivalent to a “rare” one-in-200-year event.
Dr Ashim Sattar, a glaciologist at the Indian Institute of Technology, Bhubaneswar and the lead author of the study, tells Carbon Brief the sheer scale of impact is not always evident in satellite images. He explains:
“Here, 270m cubic metres of sediment was eroded, enough to fill 108,000 Olympic swimming pools. The South Lhonak Lake itself is 2.2km long. Just walking around it will make you sweat.”
Two hours later, the GLOF and huge volumes of eroded sediment reached the village of Chungthang 35km away, destroying the 1,200MW Teesta-III hydropower project on impact and damaging four other dams downstream.
Exclusive visuals from completely damaged Chungthang Dam in Sikkim
Received from Pokhraj Rai Ji pic.twitter.com/x9gFxs1PC6
— Weatherman Shubham (@shubhamtorres09) October 12, 2023
As the GLOF travelled, it set off 45 secondary landslides, many of them deep-seated and up to 150 metres in depth, with impacts not just in Sikkim, but also in neighbouring West Bengal and Bangladesh.
In all, the flood cascade damaged 25,900 buildings, 31 major bridges and flooded 276km2 of agricultural land. The most heavily inundated zone was in Bangladesh 300km away, where intense cyclonic rainfall – initially attributed as a main GLOF driver – exacerbated flooding.
The figure below, taken from the study, shows before-and-after images and illustrations of the moraine collapse and the flood’s path from Sikkim to Bangladesh, where floodwaters finally discharged into the Brahmaputra river.
Dr Jakob Steiner, a geoscientist at the University of Graz and a member of the Himalayan University Consortium, who was not involved in the study, says the assessment captures the “cascading” impacts of GLOFs and their interaction with other complex, climatic factors in great detail. He tells Carbon Brief:
“Even if the glacial lake is relatively small, it can trigger other movements downstream and that can have far-reaching consequences, even for hydropower plants miles away from any lakes. So the message [of the study] is that you’re not safe anywhere and, hopefully, that’s a message that policymakers will get. Institutionally, however, we are not yet prepared to receive that kind of message.”
What caused the flood?
To study such a complex and multifaceted event, researchers combined satellite imagery, meteorological data, field observations and numerical modeling.
Study lead Sattar tells Carbon Brief that “capturing this entire process into one model is very tricky and complex”.
Throughout the paper, the authors emphasise the “multi-hazard” nature of the disaster, explaining that multiple short- and long-term changes in the climate and terrain converged to create the conditions needed for the event.
However, Sattar tells Carbon Brief that the “main driver” of the GLOF was the long-term impact of rising temperatures on permafrost – the perennially frozen ground that makes up much of the mountain’s slope.
According to the authors, decades of rising temperatures have led to permafrost thaw, which caused “extensive, rapid deformation” of the slope for years preceding the collapse. The paper estimates that permafrost warming has reached a depth of 100 metres below the surface of the soil.
The study also identifies the expansion of the South Lhonak lake as an important driver. The authors find that the South Lhonak glacier, which sits above the lake, has been melting for decades. Meltwater from the glacier flows directly into the lake, which has been gradually filling up.
The charts below show the annual mass balance of the glacier (left) – where a negative number indicates a shrinking glacier – and the increasing area of the lake (right) between 1951 and 2023.
The research finds that the lake has been expanding by 0.32km2 per year over 1975-2023. It notes there has been a “doubling” in the rate of expansion over the past two decades.
The authors suggest that rising temperatures are responsible for the glacier losing mass, as the annual average temperature in the region has been increasing by 0.08C per decade since the 1950s.
The long-term permafrost thaw and growth of the lake means that, by October 2023, the region was in a state of “increased sensitivity” to a multi-hazard cascade, the paper says.
The authors say the final “trigger” was the intense rainfall that hit Sikkim on 3-4 October. Though the rainfall was “typical” for the region and season, the authors say that it “saturated the soil and increased the vulnerability of slopes to failure”.
Dr Stephan Harrison – a researcher from the University of Exeter – tells Carbon Brief that the study is “very significant” and is “written by some of the leading scientists in the field”.
Dr Miriam Jackson is the programme coordinator for the cryosphere initiative at the International Centre for Integrated Mountain Development, and was not involved in the study. She echoes Harrison’s praise, but warns about the “lack of good data” in the region for these sorts of studies. She says:
“We desperately need more data on the status of glaciers and glacial lakes, more meteorology measurements at high elevation and more data on the status of frozen ground in the Hindu Kush Himalaya.”
Harrison and Jackson gave conflicting answers about whether GLOFs are increasing or decreasing globally. However, both pointed to the lack of data on GLOFs, noting that datasets are incomplete or unavailable in many regions and emphasised the need to get better records before definitive answers can be drawn.
Hydropower rush
The Sikkim GLOF event joins a chain of recent disasters in high-mountain Asia that have destroyed hydropower plants. Given the sheer “physical magnitude” of these events and their impacts, the study highlights “potential limits to adaptation” in the Himalaya, warning that “even the most diligent and comprehensive suite of disaster risk reduction strategies [is] unlikely to entirely prevent” loss and damage.
The study draws attention to a “surge” of hydropower development in the Himalayan region near glacial lakes, which it attributes to a rising demand for “stable and renewable energy”.
With more than 650 projects planned or under construction in high-mountain Asia, it warns that many dams are “moving closer to these hazard-prone areas” and this could “exacerbate” GLOF impacts. The Teesta basin, for instance, hosts the highest density of hydropower projects in the Himalayan region, with 47 dams planned, including the reconstruction of the Teesta-III project.
While dams themselves are “susceptible” to a wide array of high-mountain hazards, they also increase the exposure of communities, workers and infrastructure investments to a “greater likelihood” of GLOFs in the future, according to the paper.
Comprehensive risk assessments, stringent building standards, regulating land use and regional cooperation among river-sharing countries are among the measures suggested by the study to reduce GLOF risks.
Sattar says governments “can make a start” by developing “basin-scale” early-warning systems. However, he cautions that structural measures such as draining glacial lakes “are easy to say, but difficult to do” in harsh terrain.
Meanwhile, geoscientist Steiner says it is critical that the key role played by infrastructure development in damage caused by GLOFs is not downplayed – noting that a failure to do so risks “absolv[ing] local institutions of their responsibility”. He concludes:
“As scientists, we find it important to show that climate change is involved, but we have to be aware that the science we create is very, very political… [A] big part of the disaster is not climate change; it’s institutional failures, it’s infrastructural failures.
“If nobody takes the responsibility and everyone just says: ‘it’s my neighbour and not me’, then we are truly in deep shit. Maybe we already are.”
The post ‘Catastrophic’ 2023 lake outburst in India driven by glacial melt and permafrost thaw appeared first on Carbon Brief.
‘Catastrophic’ 2023 lake outburst in India driven by glacial melt and permafrost thaw
The governor’s office said the city’s two main reservoirs could dry up by May, much sooner than previous timelines. But authorities still offer no plan for curtailment of water use.
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Lena Luig is the head of the International Agricultural Policy Division at the Heinrich Böll Foundation, a member of the Global Alliance for the Future of Food. Anna Lappé is the Executive Director of the Global Alliance for the Future of Food.
As toxic clouds loom over Tehran and Beirut from the US and Israel’s bombardment of oil depots and civilian infrastructure in the region’s ongoing war, the world is once again witnessing the not-so-subtle connections between conflict, hunger, food insecurity and the vulnerability of global food systems dependent on fossil fuels, dominated by a few powerful countries and corporations.
The conflict in Iran is having a huge impact on the world’s fertilizer supply. The Strait of Hormuz is a critical trade route in the region for nearly half of the global supply of urea, the main synthetic fertilizer derived from natural gas through the conversion of ammonia.
With the Strait impacted by Iran’s blockades, prices of urea have shot up by 35% since the war started, just as planting season starts in many parts of the world, putting millions of farmers and consumers at risk of increasing production costs and food price spikes, resulting in food insecurity, particularly for low-income households. The World Food Programme has projected that an extra 45 million people would be pushed into acute hunger because of rises in food, oil and shipping costs, if the war continues until June.
Pesticides and synthetic fertilizer leave system fragile
On the face of it, this looks like a supply chain issue, but at the core of this crisis lies a truth about many of our food systems around the world: the instability and injustice in the very design of systems so reliant on these fossil fuel inputs for our food.
At the Global Alliance, a strategic alliance of philanthropic foundations working to transform food systems, we have been documenting the fossil fuel-food nexus, raising alarm about the fragility of a system propped up by fossil fuels, with 15% of annual fossil fuel use going into food systems, in part because of high-cost, fossil fuel-based inputs like pesticides and synthetic fertilizer. The Heinrich Böll Foundation has also been flagging this threat consistently, most recently in the Pesticide Atlas and Soil Atlas compendia.
We’ve seen this before: Russia’s invasion of Ukraine in 2022 sparked global disruptions in fertilizer supply and food price volatility. As the conflict worsened, fertilizer prices spiked – as much from input companies capitalizing on the crisis for speculation as from real cost increases from production and transport – triggering a food price crisis around the world.
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Since then, fertilizer industry profit margins have continued to soar. In 2022, the largest nine fertilizer producers increased their profit margins by more than 35% compared to the year before—when fertilizer prices were already high. As Lena Bassermann and Dr. Gideon Tups underscore in the Heinrich Böll Foundation’s Soil Atlas, the global dependencies of nitrogen fertilizer impacted economies around the world, especially state budgets in already indebted and import-dependent economies, as well as farmers across Africa.
Learning lessons from the war in Ukraine, many countries invested heavily in renewable energy and/or increased domestic oil production as a way to decrease dependency on foreign fossil fuels. But few took the same approach to reimagining domestic food systems and their food sovereignty.
Agroecology as an alternative
There is another way. Governments can adopt policy frameworks to encourage reductions in synthetic fertilizer and pesticide use, especially in regions that currently massively overuse nitrogen fertilizer. At the African Union fertilizer and Soil Health Summit in 2024, African leaders at least agreed that organic fertilizers should be subsidized as well, not only mineral fertilizers, but we can go farther in actively promoting agricultural pathways that reduce fossil fuel dependency.
In 2024, the Global Alliance organized dozens of philanthropies to call for a tenfold increase in investments to help farmers transition from fossil fuel dependency towards agroecological approaches that prioritize livelihoods, health, climate, and biodiversity.
In our research, we detail the huge opportunity to repurpose harmful subsidies currently supporting inputs like synthetic fertilizer and pesticides towards locally-sourced bio-inputs and biofertilizer production. We know this works: There are powerful stories of hope and change from those who have made this transition, despite only receiving a fraction of the financing that industrial agriculture receives, with evidence of benefits from stable incomes and livelihoods to better health and climate outcomes.
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Inspiring examples abound: G-BIACK in Kenya is training farmers how to produce their own high-quality compost; start-ups like the Evola Company in Cambodia are producing both nutrient-rich organic fertilizer and protein-rich animal feed with black soldier fly farming; Sabon Sake in Ghana is enriching sugarcane bagasse – usually organic waste – with microbial agents and earthworms to turn it into a rich vermicompost.
These efforts, grounded in ecosystems and tapping nature for soil fertility and to manage pest pressures, are just some of the countless examples around the world, tapping the skill and knowledge of millions of farmers. On a national and global policy level, the Agroecology Coalition, with 480+ members, including governments, civil society organizations, academic institutions, and philanthropic foundations, is supporting a transition toward agroecology, working with natural systems to produce abundant food, boost biodiversity, and foster community well-being.
Fertilizer industry spins “clean” products
We must also inoculate ourselves from the fertilizer industry’s public relations spin, which includes promoting the promise that their products can be produced without heavy reliance on fossil fuels. Despite experts debunking the viability of what the industry has dubbed “green hydrogen” or “green or clean ammonia”, the sector still promotes this narrative, arguing that these are produced with resource-intensive renewable energy or Carbon Capture and Storage (CCS), a costly and unreliable technology for reducing emissions.
As we mourn this conflict’s senseless destruction and death, including hundreds of children, we also recognize that peace cannot mean a return to business-as-usual. We need to upend the systems that allow the richest and most powerful to have dominion over so much.
This includes fighting for a food system that is based on genuine sovereignty and justice, free from dependency on fossil fuels, one that honors natural systems and puts power into the hands of communities and food producers themselves.
The post Middle East war is another wake-up call for fossil fuel-reliant food systems appeared first on Climate Home News.
Middle East war is another wake-up call for fossil fuel-reliant food systems
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