Two years ago this month, a flood devastated the Himalayan village of Kedarnath, India, the destination of half a million Hindu pilgrims annually. The town sits 11,500 feet up in a tight valley. Sharp, snowy peaks tower on three sides and a stone temple sits at one end. The flood — which occurred on June 17, 2013 — was India’s worst disaster in a decade. Several thousand people drowned. The deluge tore apart dozens of bridges, swept away miles of paved roads, and carried off herds of livestock.

Government officials, scientific researchers, and media commentators soon speculated about the cause of the flood and about why so many people had died. They pointed to the early and heavy monsoon rains. They railed against poorly built homes, unregulated development along the Mandakini River that runs through Kedarnath, and soil erosion caused by thousands of pilgrims trekking on foot and on donkeys to reach this remote town in the northern Indian state of Uttarakhand.

All these factors contributed. Yet in the two years since the flood, scientists studying with the care and intensity of forensic investigators have added another key cause: global warming. In recent papers, they conclude that melting glaciers and shifting storm tracks may soon set off more catastrophic floods in mountainous regions of India and adjacent countries. Atmospheric scientists say that in northern India the intense rains that preceded the disaster are extremely rare. But they have discovered that an unusual collision of weather systems steered storms over Uttarakhand and locked them in place, pouring rain down for days. Long-term changes in weather patterns are making such collisions more likely, a development that some scientists believe is caused by global warming. Global warming has is also melting glaciers all over the Himalayas, including one perched above Kedarnath. Some researchers say that had the glacier remained healthy, heavy rain alone would not have destabilized a gravel bank that collapsed, releasing a destructive pulse of debris-filled water.