Over 5000 people remain missing and more than 1300 people lost their lives in a tragic avalanche and debris flood near the China – Nepal border in late August. It will be recorded as one the most catastrophic natural hazards in history, and much of it played out on social media. In the aftermath, an array of theories like climate change, landslides, permafrost thaw, earthquakes and glacial destabilization were presented. A study released on September 17 by a collective of scholars called World Weather Attribution has provided new insight on what caused this tragic event.

A Review Of What Happened

A mass of rocks, debris, and ice fell from 5,150 meters above sea level to 3,750 meters. So much energy was released that it registered as an earthquake. “As the ice, rock and debris moved rapidly down the mountain, friction and mechanical energy probably caused some of the glacier ice to melt, producing large amounts of meltwater,” according to a WWA press release .

The debris flood likely had water from glaciers, permafrost, soil beneath the glacier and the rivers. The force of ice, debris, sediment and water was simply too much for bridges, homes, agricultural fields, and other human structures. It puts into perspective the sheer force of natural materials, destabilized landscapes, and gravity. Unfortunately, this human tragedy is still unfolding.

New Insights On Why It Happened

Here is the bottom line. “While the underlying geological structure controlled where and how the slope failed, longer-term warming and changing precipitation phase from snow to rain may have reduced its stability by weakening ice-filled fractures and rock–ice contacts and increasing water pressure,” explained the WWA press release. This finding is important because it aligns with something climate scientists and climate skeptics both said. Climate change did not necessarily “cause’” this event. However, there is a “but” that comes along with that statement. “Climate change is thus best understood as a destabilising factor acting on a pre-existing geological predisposition, rather than the fundamental cause of the failure,” The report went on to say.

Candidly, scientists, military organizations, and other organizations have understood climate change as a threat multiplier or accelerant for decades. Nearly a decade ago I wrote , “The Death To One Of The Most Abused Questions Ever: Was That Caused By Climate Change?” explained why the “Did Climate Change Cause The Event?” is a problematic question. I argued that more contextual framing was needed. Climate change is a crisis of our generation, and its impacts do not need hyperbole. They are catastrophic enough on their own, but proper framing is required to anchor credibility. More recently, I stated in Forbes.com , "Let’s let the analyses play out, but it certainly is not a stretch to suggest that warming temperatures, thawing permafrost and a collapsed glacier factored into this tragic mix.

What Could Have Been Done?

Many human settlements are along river systems in Nepal. Over the years, a credible early warning system has emerged to warn about typical riverine flooding. Unfortunately, there was nothing typical about this flood. “It was beyond the design and predictive limits of existing risk reduction measures, and no existing early warning system could have provided sufficient lead time or prevented the scale of impacts observed in the worst-affected areas, highlighting the limits of adaptation,” said the WWA report. A complex mix of warming at the third Pole (Himalayas), glacial mass loss, thawing permafrost, destabilized landscapes due to previous earthquake activity in the region, and socio-economic vulnerability further amplify risk. It is a classic case of risk being a function of exposure to natural hazards, the degree of vulnerability, and the ability to recover.

In 2024, I co-authored a report with colleagues for the National Academies that examined compound disasters that affected the U.S. Gulf Coast during the period of 2020 to 2021. The Nepal disaster is a classic example of a compound, cascading event. What does that really mean? “To guide its exploration of this topic, and for the purposes of this study, the committee characterizes a compounding disaster as the result of overlapping, concurrent, or successive disruptive events that affect the societal, governmental, and/or environmental functions of a community or region and diminish the community’s capacity to recover and resume essential activities,” Our committee wrote. “The weakening of these interrelated functions inhibits and prolongs the disaster recovery period, making communities more likely to experience amplified negative effects of future disruptive events,” We went on to say. In the discussion, we also noted that some communities have “disproportionate risk of suffering the effects of compounding disasters.” That’s exactly what is playing out in Nepal and will for years to come.

I watched with interest as people dug into their tribes of “causation” in the aftermath of this event. From my lens, I knew that it was a compound disaster with multiple contributing factors. That’s unfortunately our reality going forward. Heat waves and tropical cyclones also happen naturally, but we now live in a world that includes accelerants and amplification of those events. We will need to design, adapt, and prepare accordingly.