Declassified spy satellite images show that glaciers in the Himalayas are melting at double the rate since the turn of the century due to climate change
Rising global temperatures are ravaging the Himalayas, and the pace at which glaciers are melting has doubled since 2000, posing a serious threat to millions of people living in Asia, according to a new study based on 40 years of declassified spy satellite data.
The study — Acceleration of ice loss across the Himalayas over the past 40 years — that was published on Wednesday in the Science Advances journal, says Himalayan glaciers have lost some eight million gallons of water every year in recent times. They have shrunk by a foot and a half every year since the year 2000, melting at an alarming pace, much faster than in the previous 25 years.
“Our results indicate that glaciers across the Himalayas experienced significant ice loss over the past 40 years, with the average rate of ice loss twice as rapid in the 21st century compared to the end of the 20th century,” the study’s authors said. “Our analysis robustly quantifies four decades of ice loss for 650 of the largest glaciers across a 2,000 km transect in the Himalayas. We find similar mass loss rates across sub-regions and a doubling of the average rate of loss during 2000–2016 relative to the 1975–2000 interval.”
The authors, led by Joshua M. Maurer of Lamont-Doherty Earth Observatory of Columbia University in the US, stitched together declassified analogue images from US spy satellites to form a three dimensional digital image of the Himalayas as they existed more than 40 years ago. By comparing the model with present day images, they found that glaciers in the mountain range are melting at double the rate since 2000 compared with the period between 1976 and 2000. The 650 glaciers studied by the researchers represent some 55% of the region’s ice mass.
Climate change to blame
The scientists have held human-caused climate change the main culprit behind this accelerated melting. “It looks devastating and there is no doubt in my mind, not a single grain of doubt, that (the impact of climate change) is what we are seeing,” lead author Maurer told the Guardian newspaper.
Earlier in February, a landmark report by the International Centre for Integrated Mountain Development (ICIMOD) warned that the mountains in the Himalayas were likely to lose as much as third of their total ice by the end of this century even if national governments across the globe meet the Paris Agreement’s aspirational goal of keeping global temperature rise within 1.5 degrees Celsius compared with the pre-industrial average.
The comprehensive report — The Hindu Kush Himalaya Assessment — had said that a global rise of 2 degrees Celsius could melt half the glaciers in the Hindu Kush Himalaya (HKH) region, which would destabilise Asia’s rivers, severely affecting almost half of humanity.
“Global warming is on track to transform the frigid, glacier-covered mountain peaks of the HKH cutting across eight countries to bare rocks in a little less than a century. Impacts on people in the region, already one of the most fragile and hazard-prone mountain regions in the world, will range from an increase in extreme weather events, a reduction in agricultural yields and more frequent disasters,” Philippus Wester of ICIMOD, who led the report, had said. “But it’s the projected reductions in pre-monsoon river flows, due to decreased snow melt, and changes in the monsoon that will hit hardest, throwing urban water systems and food and energy production off kilter.”
Glaciers in the high mountains of Asia make a substantial contribution to the water supply of millions of people. The complex monsoon-dependent climate of South Asia makes it difficult to pinpoint the precise reason for the melting of the ice, says the new study based on satellite images.
However, its authors said that since the ice losses are consistent throughout the region and on different types of glaciers, it suggests climate change is the main driver. “We see a close correlation between rising temperatures and ice loss accelerating,” Maurer told the National Geographic magazine.
A letter by scientists published in the Nature journal in September 2017 had said that about two-thirds of the region’s ice would be lost with the expected rise in global temperatures. Temperatures are rising faster in the high-altitude regions compared with the plains, the scientists had said. The latest study points to a similar direction.