It is now quite clear that 2020 is going to be either the warmest or the second warmest year since records began, according to climate data analysed by the UK-based climate science and policy website Carbon Brief. It looked at global surface temperature records for 2020 from six different research groups including NASA, the UK Met Office, the US National Oceanic and Atmospheric Administration (NOAA) and Berkley Earth. Despite neutral El Niño conditions this year (unlike in 2016, the current hottest year, when El Niño conditions boosted warming), 2020 could still go top, an alarming fact.
In this year of heat records, especially in the first half of the year, the Arctic has been one of the worst hit regions. First there was a heatwave that swept through much of the region, especially in north Siberia, a region that was almost 7 degrees Celsius hotter than pre-industrial times. This was followed by forest fires in the Arctic Circle in June and record low levels of Arctic summer sea ice for large parts of July. There have also been scientific reports predicting that most polar bear sub-populations will suffer starvation and reproductive failure by 2040 as a result of melting summer sea ice, and disappear entirely by 2100. Other studies have revealed that the Earth has lost 28 trillion tonnes of ice in the past 23 years, raising global sea levels at the rate of .77mm a year.
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To add to this, a study released on 27 October states that the accelerating depletion of Arctic summer sea ice is about to trigger a vicious climate feedback loop. Authored by scientists at the Potsdam Institute for Climate Impact Research, Global Warming Due To Loss Of Large Ice Masses And Arctic Summer Sea Ice, published in Nature Communications, looks at the extent to which the complete disappearance of Arctic sea ice by 2050 will affect global warming. As sea ice melts and gives way to open water, the albedo effect of white ice reflecting sunlight back into space gives way to more heat being absorbed by dark sea water. The study says that if global temperatures rise by 1.5 degree Celsius over pre-industrial times, then the combined loss of ice from global mountain glaciers, the Greenland ice sheet and the West Antarctica ice sheet will add an extra warming of .43 degrees Celsius. This, the scientists say will probably occur over a longer time horizon measured in centuries, but that human actions will trigger this long-term change in just a few decades.
The immediate feedback from Arctic melting will be felt sooner. The study says that, “the decay of the Arctic summer sea ice would exert an additional warming of 0.19 °C at a uniform background warming of 1.5 °C above pre-industrial.” Even such a seemingly small increase is a big deal. For comparison, according to Berlin-based climate-science institute Climate Analytics’s Climate Action Tracker (CAT), China going carbon neutral by 2060 would lower global warming by about 0.2 degrees Celsius. According to the CAT, this would be the single biggest reduction ever. As Ricarda Winkelmann, one of the authors of the study, puts it, “Every tenth of a degree of warming counts for our climate. Preventing Earth system feedback loops, or vicious circles, is thus more urgent than ever.”
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FIRST PUBLISHED29.10.2020 | 11:00 AM IST
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