KEY FINDINGS
The landmark UN report on limiting global warming to 1.5 degrees Celsius was released in South Korea yesterday after a week-long meeting of the 195-nation Intergovernmental Panel on Climate Change (IPCC). Here are key findings, grounded in some 6,000 peer-reviewed scientific studies:
'UNPRECEDENTED CHANGES'
Capping global warming at 1.5C above pre-industrial levels will require "rapid, far-reaching and unprecedented changes in all aspects of society", the IPCC said. Earth's average surface temperature has already gone up 1C -- enough to unleash a crescendo of deadly extreme weather -- and is on track to rise another two or three degrees absent a sharp and sustained reduction in carbon pollution. At current levels of greenhouse gas emissions, we could pass the 1.5C marker as early as 2030. To have at least a 50-50 chance of staying under 1.5C without overshooting the mark, the world must, by 2050, become "carbon neutral".
STEEP COST OF INACTION
The 30-page executive summary also details humanity's "carbon budget" -- the amount of CO2 we can emit and still stay under the 1.5C ceiling. For a two-thirds chance of success, that is about 420 billion tonnes, an allowance that would -- according to current trends -- be used up in a decade. The share of electricity generated by renewables -- mainly hydro, solar and wind -- would have to jump by mid-century from about 20 to 70 percent. The share of coal, meanwhile, would need to drop from 40 percent to low single digits. Limiting global warming to 1.5C will require investing about $2.4 trillion (2.1 trillion euros) in the global energy system every year between 2016 and 2035.
1.5C VS 2C
Two degrees Celsius was long considered the temperature guardrail for a climate-safe world, but a raft of recent research shows otherwise. "Climate impacts are exponentially more dramatic when we go from 1.5C to 2C," said Henri Waisman, a scientist at the Institute for Sustainable Development and International Relations, and a coordinating lead author of the IPCC report. Some tropical fisheries are likely to collapse somewhere between the 1.5C and 2C benchmark. Staple food crops will decline in yield and nutritional value by an extra 10 to 15 percent. Coral reefs will mostly perish. The rate of species loss will accelerate "substantially".
PATHWAYS
IPCC authors say the 1.5C goal is technically and economically feasible, but depends on political leadership to become reality. One pathway, for example, relies heavily on a deep reduction in energy demand, while another assumes major changes in consumption habits, such as eating less meat and abandoning cars with internal combustion engines. Two others depend on sucking massive amounts of CO2 out of the air, either though large-scale reforestation, use of biofuels, or direct carbon capture.
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