Planetary Energy Imbalance, ENSO Variability and Cryospheric Instability: A Multi-Scale Analysis of Himalayan Climate Risk and the 2026 Nepal Flood

The Earth is constantly balancing a budget of energy. It receives a steady stream of heat from the Sun and radiates a matching amount back into space. For most of human history, this balance has held steady. However, as greenhouse gases have accumulated in the atmosphere, the planet has begun to trap more heat than it releases. Scientists call this the Earth's energy imbalance. It is not a sudden spike but a slow, persistent accumulation of extra heat, much like a bank account where deposits consistently exceed withdrawals. This excess energy does not vanish; it flows into the oceans, warming the water, and into the land and ice, causing glaciers to melt and permafrost to thaw. In the high mountains of the Himalayas, this warming changes the physical rules of the landscape. Ice that once acted as a glue holding rocks together begins to melt, and water seeps into cracks, altering the stability of steep slopes. When these slow, planetary changes meet sudden weather events or geological weaknesses, the result can be catastrophic.

A new study published in September 2026 by C. S. A. Raj of Arul Anandar College examines how these global shifts connect to a specific, devastating event: the massive flood that struck the Rasuwa and Langtang Lirung regions of Nepal on August 26, 2026. The research does not attempt to prove that global warming alone caused this disaster. Instead, it builds a detailed picture of how long-term planetary heating sets the stage for such tragedies, while short-term weather and local geology decide exactly when and where they happen. The author uses existing data from satellites, weather stations, and government reports to trace the chain of events, moving from the global scale of energy accumulation down to the local scale of a collapsing mountain face.

The study begins by looking at the big picture. Observations from satellites show that the Earth's energy imbalance has roughly doubled in the last two decades, rising from about 0.5 watts per square meter in the early 2000s to about 1.0 watts per square meter more recently. This extra energy is the engine of long-term climate change. While the oceans absorb most of this heat, the high mountains feel the effects in a very specific way. The research highlights that the freezing level—the altitude where temperatures drop below zero—is rising by about 100 meters every decade. This means that ice and snow, which once existed at lower elevations, are now melting higher up. In the Langtang region, glaciers have been losing mass steadily, shrinking by roughly half a meter of water equivalent every year between 2015 and 2019. This loss is not just a visual change; it alters the mechanical strength of the mountains.

The paper then turns to the 2026 disaster itself. On that day, a massive section of rock and ice, weighing thousands of tons, detached from the side of Langtang Lirung mountain at an elevation of about 5,150 meters. The material fell roughly 1,400 meters, transforming into a fast-moving torrent of debris and water that reached the border town of Rasuwagadhi, 22 kilometers away, in just seven minutes. The study reconstructs this event by combining several layers of evidence. It notes that the slope was geologically weak, a condition that may have been influenced by the massive 2015 earthquake, which left the terrain fractured and unstable. However, the research clarifies that the specific contribution of the earlier earthquake to the 2026 collapse cannot yet be quantified. Instead, the decades of warming had degraded the permafrost and melted the ice that helped bind the rocks together.

A crucial part of the analysis involves understanding the role of short-term weather patterns, specifically the El Niño-Southern Oscillation, or ENSO. In 2026, the climate system was shifting toward an El Niño phase, a natural cycle that can bring warmer and wetter conditions to parts of the world. The study clarifies that while this weather pattern may have influenced the local conditions on the day of the disaster, it was not the sole cause. The author is careful to distinguish between the background conditions created by long-term warming and the immediate triggers. They argue that treating ENSO or global warming as a single, direct cause of the flood is a mistake. The disaster was a compound event, where the slow accumulation of planetary heat weakened the mountain over years, while the specific weather on that day and the underlying geology provided the final push.

The research clarifies that the revised analysis does not use the phrase "cosmic warming" to claim that solar or cosmic forcing is the primary explanation for contemporary global warming. Instead, the evidence supports anthropogenic radiative forcing as the fundamental driver of the long-term warming trend, while acknowledging that solar variability, clouds, aerosols, and internal variability can affect components of the Earth's radiation budget. It moves away from the notion that global warming "caused" the event in a simple, linear way. Instead, the paper proposes a multi-scale framework. In this view, the Earth's energy imbalance acts as a slow, persistent force that changes the boundary conditions of the entire mountain system. It thaws the ice, raises the snowline, and increases the water pressure in the rocks. Over time, these changes make the slopes more vulnerable. Then, a combination of local geological weakness and a short-term weather event triggers the failure. The study suggests that the 2026 flood was the result of this complex interaction, where the mountain was already primed for failure by decades of warming, waiting for a final trigger.

To manage such risks in the future, the paper argues that current warning systems are insufficient. Most early warning systems focus on rainfall or river levels, which are useful but incomplete. The study suggests that a more effective approach would integrate monitoring of the cryosphere—the frozen parts of the Earth. This would include tracking the movement of glaciers, measuring the temperature of permafrost, and observing rock deformation. By watching these slow-moving indicators alongside fast-changing weather data, scientists could better understand when a mountain is becoming unstable. The research also emphasizes the need for cross-border cooperation, as rivers and hazards in the Himalayas do not respect political boundaries. Sharing data between countries like Nepal and India could provide a clearer picture of the risks facing the entire region.

Ultimately, the paper reframes how we understand mountain disasters. It moves the conversation away from searching for a single culprit and toward understanding a cascade of processes. The Earth's energy imbalance is the long-term driver, warming the planet and altering the landscape. The Himalayan cryosphere is the sensitive interface where this warming becomes visible and mechanically dangerous. Local geology and short-term weather are the final actors that determine the timing of the collapse. The 2026 Rasuwa disaster serves as a stark example of this chain reaction. It was not a random accident, nor was it caused by one thing. It was the result of a planet warming up, a mountain losing its icy glue, and a specific day when the ground finally gave way. The study concludes that to protect lives and infrastructure, we must monitor all these pieces together, recognizing that the danger lies in the connection between the global and the local.