UN admits 1.5°C limit will be breached, maps overshoot path

A UN Environment Programme report concedes the 1.5°C warming target will be exceeded within years, proposing an 'overshoot' strategy where temperatures peak then cool. The world faces decades of worsening disasters, food shortages, and sea-level rise even under optimistic scenarios, per the report.

Bottom line — UNEP projects warming peaking at 1.8°C under ambitious policies, but current policies lead to 2.6°C by 2100.

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• The report, released on 1 September, says the 1.5°C threshold will be crossed 'in the next few years' and that the planet is now at 1.4°C above pre-industrial levels, according to AP.
• UNEP Executive Director Inger Andersen said the goal remains but must now be approached 'from above', per Nature.
• Report co-author Richard Betts of the University of Exeter called it a 'reality check' and said the overshoot period will last 'many, many decades', AP reports.
• The most optimistic scenario sees warming peaking at 1.8°C around mid-century if ambitious climate goals are pursued, but current policies would push temperatures to 2.6°C by 2100, per the report.
• Every five years of delay in reducing emissions adds at least 0.1°C to peak warming, said co-author Joeri Rogelj of Imperial College London, according to AP.
• The report warns of irreversible tipping points including loss of the West Antarctic and Greenland ice sheets, Amazon rainforest dieback, and shutdown of the Atlantic Meridional Overturning Circulation (AMOC), which could plunge Europe into severe winters, Yale E360 reports.
• Stanford climate scientist Rob Jackson, not involved in the report, said overshoot scenarios require 'stopping the train quickly and backing it up', calling it 'our best hope' but 'absolutely not likely', per AP.
• Carbon removal via tree planting can shave at most 0.1°C off global temperatures, so novel approaches are needed, the report states, according to AP.
• The Global Tipping Points Report led by Tim Lenton of the University of Exeter warns that multiple Earth system tipping points are approaching, with devastating consequences, Yale E360 notes.
• James Hansen of Columbia University forecasts 2°C warming as soon as 2045 under a high-emissions scenario, per Yale E360.
• Natural carbon sinks are weakening: oceans are becoming more stratified and African rainforests have turned from a carbon sink to a source, Yale E360 reports.

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