By Bill McGuire
In my last blog I reported on the unsurvivable heatwaves that lie in wait, later this century, for unsuspecting populations, particularly across Asia. Without serious efforts to slash global carbon emissions now, three quarters of the population of India will be exposed to ‘extremely dangerous’ levels of humid heat, while four hundred million inhabitants of China’s northern plain will be at severe risk of heat death.
This is shocking enough in its own right, but this week brought more bad news for the region that looks, increasingly, as if it will occupy an unenviable position in the front line as our world’s climate continues to break down. The huge populations of nations like India, China and Pakistan are only sustainable while there is a reliable food supply. This, in turn, is critically dependent upon a trustworthy supply of water for irrigation. There have been worries for some time that a failing climate will result in a more sporadic monsoon, or even – on occasion – its failure. The new research, however, brings an even greater threat.
According to the results of a new landmark study1, the glaciers of the 3,500-long Hindu Kush Himalaya mountain chain are in such a precarious state that a business as usual emissions scenario will see two-thirds of them gone by the century’s end. Even if we really pull our fingers out and slash emissions so as to keep the global average temperature rise below 1.5°C, one third of the ice will still be gone by 2100.
The reason why this scenario is so potentially cataclysmic is that the great rivers draining the Hindu Kush Himalaya – including the Indus, Ganges, Mekong, Yangtze and Yellow – provide the water that irrigates the crops that feed two billion people across a region stretching from Afghanistan and Pakistan in the west to China and Myanmar in the east. Cut off this water supply and the stage is set for a prodigious famine far beyond biblical proportions. The study is the work of more than 200 scientists and peer reviewed by a further 150, so it stands as a formidable work of climate science that cannot and must not be ignored.
With 15 percent of the ice already gone, since the 1970s, problems are already becoming apparent due to more erratic river flow. By the middle of the century, the authors of the report predict, river flow will ramp up as more and more meltwater cascades down from the mountains. Flood events will occur far more frequently, while population centres will also face existential danger from catastrophic deluges arising from the breaching or overtopping of high-altitude meltwater lakes.
The real problems will set in, however, from around the 2060s onwards, as river flows start to drop off in earnest as the source ice fields fade away. Not only will this have a devastating impact on agriculture, it will also ensure that hydro-power dams on the rivers can no longer function, cutting power across the region. The prospects of billions being unable to feed themselves while at the same time having insufficient power to attend to the basics of life, doesn’t bear thinking about. This is a pending human catastrophe on the grandest of scales, and yet another reason why we can’t afford to dither any longer. The honest truth is that, even if we manage to achieve net zero emissions by 2025, this still won’t be enough to stop climate breakdown in its tracks. But failing to do this will doom vast tracts of our world to the heat, dust and despair of Hothouse Earth.
1The Hindu Kush Himalaya Assessment
Bill McGuire is Professor Emeritus of Geophysical & Climate Hazards at UCL and author of Waking the Giant: How a Changing Climate Triggers Earthquakes, Tsunamis and Volcanic Eruptions. He was a contributor to the IPCC 2012 report on Climate Change & Extreme Events and Disasters.