CUET English Language Comprehension Passage 18 — Flashcards

Global warming this century could trigger a run away thaw of Greenland's ice sheet and other abrupt shifts such as a dieback of the Amazon rainforest, scientists say.    
They urged governments to be more aware of 'tripping points' in nature, tiny shifts that can bring big and almost always damaging changes such as a melt of Arctic summer sea ice or a collapse of the Indian monsoon.    
'Society may be lulled into a false sense of security by smooth projections of global change,' the scientists at British, German and American institutes wrote in a report saying there were many little-understood thresholds in nature.    
'The greatest and clearest threat is to the Arctic with summer sea ice loss likely to occur long before, and potentially contribute to, Greenland ice sheet melt', they wrote in the journal 'Proceedings' of the National Academy of Sciences. 'Tipping elements in the tropics, the boreal zone, and west Antarctica are surrounded by large uncertainty', they wrote, pointing to more potential abrupt shifts than seen in a 2007 report by the UN Climate Panel.    
A projected drying of the Amazon basin, linked both to logging and to global warming, could set off a dieback of the rainforest. Many of these tipping points could be closer.    
Other sudden changes linked to climate change, stoked by human use of fossil fuels, included a dieback of northern pine forests, or a stronger warming of the Pacific under EI Nino weather events that can disrupt weather world-wide, they wrote.    
A possible greening of parts of the Sahel and the Sahara, if monsoon rains in West Africa were disrupted, was one of the few positive abrupt shifts identified by the scientists.    
Even a moderate warming could set off a thaw of Greenland's ice sheet that could then vanish in 300 years— raising sea levels by 20 ft, or 2 meters a century and threatening coasts, Pacific islands and cities from Bangkok to Buenos Aires. The UN Climate Panel foresees a rise in world sea level ranging up to about 80 cms this century and reckons that a thaw of Greenland would take hundreds of years longer.    
The new study said a disappearance of Arctic sea ice in summer time could happen in coming decades—earlier than projected by the UN panel. That could stoke further global warming as dark water soaks up more heat than ice and snow.