It is no secret that the immediate physical effects of global heating is being observed in the way that it is melting the world’s ice, or cryosphere. A report in August last year had stated that between 1994-2017, the world had lost 28 trillion tonnes of ice, raising the global sea level by 35mm. A new study published in Nature on 28 April has now found that between 2000-2019, the world’s glaciers, including those in the Himalaya, lost 267 gigatonnes (Gt) of ice every year. This rate of melting has contributed towards 21% of global sea level rise, more than the contribution of the Antarctic and Greenland ice sheets. Global glacial mass loss in the two decades has been 47% larger than the Greenland ice sheet and over twice as much as the Antarctic ice sheet.
The study, Accelerated Global Glacier Mass Loss In The Early 21st Century, is an important contribution to our knowledge of how climate change is affecting the cryosphere. It is one of the most exhaustive analysis of the kind done till date, combining twenty years of historical satellite data from NASA and sophisticated statistical methods to cover 217,175 of the world’s glaciers, nearly 99.9% of glacier areas around the world. The researchers found that outside of the Greenland and Antarctic ice sheets, glaciers around the world have been losing mass at a rapidly accelerated pace of 62Gt per year per decade.
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While glaciers all over the world have lost mass, the study finds that 83% of the global mass loss is from seven particular regions. Alaska’s glaciers have contributed 25% of this loss, Greenland’s peripheral glaciers have contributed 13%. Glaciers in High Mountain Asia (including the Himalaya and the Karakoram range), Antarctic and Subantarctic regions and the Southern Andes have contributed 8% each.
The researchers have re-iterated earlier projections that at present rates of melting, the world’s glaciers could be gone by 2050. And apart from causing a rise in sea levels, glacial mass loss has grave implications for water security. “The situation in the Himalayas is particularly worrying. During the dry season, glacial meltwater is an important source that feeds major waterways such as the Ganges, Brahmaputra and Indus rivers. Right now, this increased melting acts as a buffer for people living in the region, but if Himalayan glacier shrinkage keeps accelerating, populous countries like India and Bangladesh could face water or food shortages in a few decades,” says Romain Hugonnet, lead author of the study and researcher at ETH Zurich and the University of Toulouse.