120 years of global warming

This year, global warming turns 120. As Bloomberg Business reports, 2016 is the 120th anniversary of the first time we figured out that human activity could be causing climate change. “Cumulative emissions of CO2 are the dominant driver of long-term temperatures”, states Professor Myles Allen, Environmental Change Institute, University of Oxford. “Past emissions, amounting to about 2 trillion tonnes of CO2, have already committed us to about 1ºC of warming.”



The history of global warming video by Alan Jeffries, Christian Capestany, Eric Roston


According to scientists, 2015 was the hottest year on record. With dramatic effects such as tornado outbreaks, major floods and extreme drought in different areas all over the world. Now, the key question is if we can hold global temperatures to a 1.5 degree rise. “On one level, the answer is very simple: if 2ºC is possible, then so is 1.ºC, albeit less likely, because we do not know precisely how the climate system will respond to future emissions, and still less how future emissions will respond to mitigation policies”, says. Allen. To stabilize at 1.5ºC, temperatures need to fall, on average, by 20% per tenth of a degree of future warming. “Right now, the world is warming by a tenth of a degree every 5-10 years, but of course that would slow as emissions fall.”


But CO2 is not the only pollutant causing warming, although it is the most persistent. “Almost all the IPCC’s scenarios project that other sources of pollution (methane, soot and the like) will add at least another 0.5ºC to this, taking the total to 2ºC.”, says Allen. “But we are only just beginning to work out how to reduce these other emissions, and in any case, it is the warming caused by CO2 that is particularly dangerous because it is so hard to reverse. “


Photo © Courtesy of USDA Natural Resources Conservation Service

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