Earth sinks with climate lethargy PDF Print E-mail
Tuesday, 01 October 2019 08:22
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 Sarthak edit


A new report from the Intergovernmental Panel on Climate Change (IPCC), on the effect of global heating on the oceans and the cryosphere, is the latest in the growing line of warnings that underscore the need for urgent climate action. Given oceans are key carbon-sinks, if governments worldwide—other than a handful, including India—choose to walk their current emission paths, the foreseeable future looks quite bleak. Over a billion lives in the high mountains, low-lying coastal zones, island-nations, and the Arctic hang in balance. Global heating at 1oC above pre-industrial levels—by 2100, it is predicted to reach 2.9oC with the “ambitious” plans of the Paris deal signatories, 3.3oC with the current emission reduction action, and 4.5oC without any action—has already had a drastic impact on ocean ecosystems. If countries don’t double down on reducing greenhouse gas emissions by radically reimagining consumption, farming and land-use, energy generation, etc, the effect on oceans and the cryosphere will worsen the climate crisis. So far, these have been part of the buffer against much worse impact.

The IPCC report, which references over 7,000 scientific publications, states that small glaciers could lose more than 80% of the current ice mass by 2100 under high emission scenarios—the kind that can be imagined for a world where the largest historical polluter, the US, and a large developing economy, Brazil, are both headed by stubborn climate-deniers. With the retreat of mountain glaciers, water availability, and quality downstream is also likely to be severely affected, with large negatives for food security, once agriculture gets impacted. While the 20th century saw sea levels rise globally by around 15 cm, it is currently rising by 3.6 mm per year—more than twice as fast. A significant rise in the sea level seems unavoidable given how the report predicts it to reach 30-60 cm by 2100, even when emissions are cut drastically to keep warming to <2oC. In a high emission scenario, the rise may be as high as 110 cm. Any additional warming over current levels, the report estimates, will cause events that occurred once per century in the past to occur every year by 2050.

By 2100, the report says, oceans will be absorbing 2-4 times more heat than they did between 1970 and now, if global heating is limited to 2oC, and 5-7 times more at higher emission levels. Given the retarding effect it will have on the mixing of water layers, and, consequently, on oxygen and nutrient availability, marine life will be severely impacted. Emissions led to marine heatwaves doubling in frequency since 1982—their frequency will be 20 times higher at 2oC warming, and 50 times higher at higher emission levels. The report also warns of unprecedented rise in ocean acidification—the oceans absorbed 20-30% of anthropogenic CO2 emissions since the 1980s.

The report also states that if global heating is stabilised at 1.5oC above pre-industrial levels, the Arctic Ocean will be ice-free only in September—the month with least ice—once every 100 years. At 2oC, there could be a year of ice-free Arctic Ocean every three years. The thawing of the permafrost is also a concern—even in a 2oC warming scenario, around 25% of the permafrost at 3-4 metre depth could thaw by 2100; nearly 70% could be lost at higher emission scenarios.

Given that the Arctic and boreal permafrosts have large amounts of organic carbon trapped in them—almost twice that in the atmosphere—any thawing is bad news, even if large-scale initiatives are taken to create carbon-sinks to offset the release. In the run up to the 25th Conference of Parties of the UN Framework Convention on Climate Change, countries need to take serious climate action. Else, the world sinks as it fries.



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