Climate change & Himalayan glaciersÂ

 (The writer is Ice and Climate Research Fellow, University of Sheffield)In the world of glaciology, the year 2007 would go down in history. It was the year a seeminglysmall error in a major international report heralded huge changes in our understanding of what was happening to the Himalayan glaciers.Just one year after Al Gore’s documentary An Inconvenient Truth sparked conversations about anthropogenic (human-made) global warming, the Intergovernmental Panel on Climate Change(IPCC) published its 4th Assessment Report. This state-of-the-science summary was the gold standard to inform the world about climate change. The report contained one small but serious error “ that all glaciers in the Himalayas would vanish by the year 2035.The scandal sparked a flurry of new research, including my own, and we can now see that someHimalayan glaciers will survive into the next century. The latest data tells us that if we reduceour greenhouse gas emissions, then between one-third and one-half of glacier ice will be lost by2100. If not, and we carry on with business as usual, then two-thirds of Himalayan glaciers willvanish by the end of this century.But how did such an error come to be presented as fact by a world-leading scientificorganisation? This is a tale of repetitions and an apparently unintended typo lending credibility toan unfounded statement. The IPCC quoted a report from the World Wildlife Foundation, whichhad taken the Himalayan meltdown date from an interview in New Scientist. That interviewquoted speculation by an Indian glaciologist, who apparently misquoted another scientist’s workpredicting glaciers worldwide would shrink by 80% by 2350.The IPCC did eventually apologise for their failure to identify this error. Although embarrassing,it did not undermine their core conclusions. The IPCC undertook to improve their peer-reviewprocess before their next report in 2013.The Himalayas are sacred mountains. Their name in Sanskrit means “abode of snow”. Butglaciers are a political issue in central Asia. Glacier-fed rivers provide water to over a billionpeople for food production and hydropower. India and Nepal in particular rely on glacier meltwater to buffer seasonal droughts before the summer monsoon. These countries are rapidlyindustrialising and generally oppose limiting their carbon emissions.After the IPCC report, the Indian government acted quickly to suppress panic witha controversial discussion paper presenting selective evidence showing that glaciers in northernIndia and Pakistan were stable or even expanding. However, the Karakoram glaciers in questionbenefit from greater winter snowfall and cooler summers as a result of global heating. Howpersistent this Karakoram anomaly will be remains unknown.Resolving a Himalayan errorGlaciologists were left wondering what the fate of Himalayan glaciers would be. Little researchwas being done and data was scarce. Problems with accessing remote, high-elevation glaciers inpolitically unstable regions deterred fieldwork. Civil war in Nepal, the Taliban in Pakistan andsuspicion of foreign scientists in China and India made these mountains difficult places to work.Field observations and surveys suggested that glaciers had not noticeably changed. Glaciologistssoon realised that changes in ice volume were hidden by rock debris on the surfaces of manylarge glaciers. So measurements of changes in glacier area were misleading and concealed thescale of ice loss.Then, in the early 2010s, rapid advances in satellite Earth observation technology anddeclassification of Cold War satellite photographs opened a window into these remotemountains. The scale of glacier change across the Himalayas could be seen for the first time.The new satellite data allowed glaciologists to measure changes in glacier volume over a 40-yearperiod. This revealed that nearly all Himalayan glaciers were shrinking at a similar rate.The future of Himalayan glaciersNew research shows that the rate at which glacier ice is lost from the Himalaya has doubled inthe last 20 years and is similar to the rate of ice loss globally. Although extreme altitudes werethought to protect glaciers from climate change, we now know that high mountains arewarming twice as fast as the rest of the planet.The proliferation of data allowed glaciologists to train computer models to project how glacierswill change in the future. These models tell us that between one-third and one-half of glacier icein the Himalaya will be lost by 2100. If we don’t act to keep climate change within theambitious Paris Agreement target of 1.5℃ then two-thirds will be lost in the same period.While the weakening of the summer monsoon and atmospheric pollution affect glacier life expectancy, rising global temperatures are causing Himalayan glaciers to shrink. These predictions are bad news for the one billion people who depend on glacier-fed rivers for water inspring at the start of the agricultural season.As glaciers decline, droughts are becoming more frequent before the summer rains, putting intense stress on populations in southern and central Asia. Governments, including India’s, have now recognised the scale of the problem. To avoid a humanitarian crisis, the world must keepglobal heating within a range that will limit glacier loss.