If Climate Change Contributed to Nepal’s Floods, Should Polluters Pay?

In the days, weeks, months, and years before a two-square-kilometer mass of glacier ice and rock collapsed from the Langtang Lirung mountain to the valley floor in Nepal’s Rasuwa district in the Himalayas—generating a debris flow that killed over 1,300 people and left 5,000 more missing—climate change was at work, conditioning the slope for failure.

That’s the conclusion of an international group of researchers that rapidly analyzed the disaster for World Weather Attribution, an initiative that studies the role climate change plays in specific extreme weather events.

For small nations like Nepal, these attribution studies are key evidence to argue for the funds they need in order to survive in a hotter world.

To pay for the disaster, Nepal’s ministries of finance and environment wrote a joint letter on August 31 to the United Nations’ Fund for Responding to Loss and Damage, set up in 2022 to support victims of the climate crisis. Nepal estimates recovery from the Rasuwa disaster to cost $4.8 billion, more than 11 percent of the nation’s GDP. They’re requesting $20 million, the maximum account countries can request of the fund, for immediate recovery and to prepare for future disasters. The country framed the request in terms of climate justice, not a request for aid. Nepal’s Foreign Minister said the country paid “the ultimate price for a global crisis [it] did not create.”

The attribution study found that atmospheric warming of 2°C, well above the global average, thawed the permafrost glueing together cracked rock walls, caused supporting glacier ice to thin and retreat, and led rain to fall at elevations where it once only snowed. Water from rain and melting ice then lubricated fractures, deep in the rock.

“We conclude this was a geologically vulnerable slope,” said Walter Immerzeel, a mountain hydrologist at Utrecht University in the Netherlands and coauthor on the study, said in a press conference.“But it was destabilized further by glacier retreat and permafrost thaw, and with excessive meltwater and exceptional warmth in the final period before the failure.”

That warming was caused by human-generated greenhouse gas emissions. The Rasuwa disaster is “yet another warning sign,” the report concludes, that climate change is transforming the world’s high mountain environments and producing the conditions for cascading hazards.

Andrew Pershing, a climate scientist not involved in the study and the chief program officer for Climate Central, another organization that conducts attribution research, compared the changing climate’s influence on the Rasuwa disaster to increasingly frequent and severe wildfires in the American West. In both cases, “climate is this preconditioner that’s putting weight on the scale towards the event,” he said. “It’s making these places much more unstable and risky to be around.”

The study’s authors point out that Nepal’s flood warning system was no match for the speed and volume of the debris flow that careened down the valley: “Events of this magnitude ultimately exceed the limits of adaptation,” they write. The takeaway should be that international “recovery and reconstruction support in impacted communities has now become an unavoidable part of climate response.”

Indeed, Nepal contributes less than 0.1 percent of annual global greenhouse gas emissions yet is experiencing the impacts of those climate-warming gasses firsthand, said Basanta Raj Adhikari, director of the Center for Disaster Studies at Tribhuvan University’s Institute of Engineering in Nepal. And because they did so little to contribute to the climate emissions that helped trigger their disaster, Nepalese leaders don’t think they should be solely responsible for paying to clean it up.

Scientists in Nepal have known for years they were vulnerable to the effects of warming temperatures—the country experiences regular glacial-lake outburst floods, which are also scientifically attributed to climate change. “We have all the evidence,” said Adhikari. “So, of course we need compensation, we need funds to combat climate change in the name of mitigation or adaptation,” he said.

Recovery will involve rebuilding infrastructure like roads and hydropower plants and relocating and rebuilding communities. To prevent repeating the same scale of devastating, Nepal also wants to design new monitoring systems to identify and track unstable rock slopes and glaciers and send timely warnings to communities downstream.

Since 2022, wealthy nations have pledged to contribute $822 million to the U.N.’s loss and damage fund, but 119 countries have since requested aid to the tune of $2.8 billion.

Early proposals for what became the loss and damage fund were framed as global insurance—countries would pay into it based on their contributions to emissions. But fierce debates followed the fund’s proposal, and powerful, high-emitting countries in the E.U. and the United States refused to accept liability for harms their greenhouse gas emissions caused in other countries. The current, voluntary fund, explicitly based on international cooperation, resulted.

But that compromise means governments and communities who did little to cause climate change are now struggling to cover the cost of it—the U.N. fund comes nowhere close to what Nepal requires.

As those affected by climate change seek damages, courts in in the U.S. and Europe have seen a swell of climate litigation in recent years.  Attribution science like the recently published WWA report are being used to link specific polluters’ emissions to harms. In 2023, Multnomah County in Oregon sued over a dozen oil companies for their role in causing the deadly 2021 Pacific Northwest heat dome, which climate attribution research had shown was “virtually impossible” without climate change. Globally, 3,600 such cases have been filed in 62 jurisdiction and 28 international courts. No plaintiff has won a liability case yet.

Scientists, however, are getting better and faster at pinpointing if and how climate change played a role in a specific disaster. Using climate models, scientists can now say definitively that a given heatwave would not have occurred in the absence of human-caused warming, then trace contribution to that warming back to specific polluters.

But outside of Europe and North America—which tend to have robust, long-term datasets—attribution science becomes tricker. Especially so with complicated, hazard-cascade-style events like the Rasuwa disaster. “Cause and effect can get very murky in these events,” Pershing, the Climate Central scientist, said.

Pre-existing bedrock weaknesses and climate drivers—plus potentially the lingering effects of the nearby 2015 Gorkha earthquake—all played a role in triggering the collapse. Scientists lack the subsurface temperature measurements, fracture-water pressures and key other data to precisely quantify how much climate change contributed—doing so would be “almost impossible” Immerzeel, the hydrologist, said.

Regardless, scientists say Nepal’s disaster bears strong hallmarks of a rapidly warming planet, increasing the risk of more rapid-onset, devastating event in mountainous regions in the future.

“The climate is changing in the Himalayas, and it’s not only the fate of the Nepali Himalayan people. There are more than two billion people living downstream, all these places are in increasing vulnerability as these events are increasing,” said Adhikari. “We are in existential threat due to climate change. We need to save our civilization in high-mountain Asia.”