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Ice melt in Greenland, by contrast, adds new water to the oceans. That raises sea levels, threatening shorelines. The new study indicates that the northeastern Greenland glacier lost stability around 2003 and has been losing some 10 million tons of ice per year since then.
Sea levels worldwide have risen about eight inches since 1900. The rate of rise began accelerating some 20 years ago, due partly to warmer water expanding and partly to melting ice. Greenland melt is believed to account for about one-sixth of the recent rise.
It was that elevated ocean surface that allowed the storm surge of Hurricane Sandy in 2012 to sweep across whole towns and pour into subway stations and electrical transformers built to withstand earlier, lower sea levels. Eight inches caused havoc.
Current projections suggest a rise of between three and six feet by 2100. What will that mean for human habitat?
As it happens, that very topic — the impact of climate change on human society — is the focus of a major report due out March 31 from the United Nation’s 195-nation Intergovernmental Panel on Climate Change.
Six years in the making, it incorporates the findings of hundreds of peer-reviewed studies by thousands of scientists in dozens of countries. It’s actually Part 2 of a three-part report that began last fall with the physical science of global warming and ends this summer with prospects for mitigating or combating the threat.
Leaked drafts of the impact report indicate that if carbon emissions continue at their current pace, rising seas will force hundreds of millions of people from homes in coastal regions around the world in coming decades.
Drought will become an ongoing crisis in some regions, as will flooding in others. Basic food crop yields will decline by an average 2% per decade, even as populations rise. The combination of food and water shortages and habitat loss will lead to hunger, mass migration and violent unrest.
One of the important points to emerge in last fall’s physical science report was that a certain amount of change and disruption is already baked into the system, even if carbon emissions were somehow reduced to zero tomorrow. The carbon dioxide pumped into the atmosphere over the past 150 years of industrialization will remain for centuries and drive planetary temperatures steadily upward. The critical question is whether continued emissions drive up the pace of warming past the point where the planet is no longer habitable.