Emissions cuts needed to minimise peak global warming, UN warns

UN scientists have warned that only deep, swift cuts to greenhouse gas emissions can keep peak global warming to 1.7C-1.8C above pre-industrial levels by mid-century, as the world braces to cross the 1.5C threshold. That breach will heighten climate dangers, yet UN secretary-general Antonio Guterres stressed that "overshoot is not surrender", with the UN Environment Programme (UNEP) setting out how countries could shrink both the size and length of the exceedance and pull warming back under 1.5C as fast as possible. The 1.5C benchmark sits at the heart of the 2015 UN Paris Agreement, under which nations pledged to hold temperature rises well below 2C while pursuing 1.5C. Researchers caution that unchecked warming will bring more frequent and fiercer extreme weather — heatwaves, droughts, wildfires and flooding — with serious fallout for people, nature and economies worldwide. It could also set off dangerous climate tipping points, inflicting lasting damage through permafrost thaw, coral reef collapse and ocean circulation failure.

Emissions Gap report findings

Those warnings appear in UNEP's latest "Emissions Gap" report, published on Wednesday. It concluded that even the “lowest possible” scenario would now mean an overshoot of 1.7C to 1.8C by mid-century, with global temperature rise returning to or below 1.5C by 2100 at roughly a 50% chance. Reaching that pathway would require cutting global emissions by 18% by 2030, 45% by 2035 and 69% by 2040, all measured against 2025 levels, the report said. Yet UNEP's experts found that countries' existing climate plans — known as nationally determined contributions (NDCs), which they must publish under the Paris Agreement — would cut emissions by only 5-8% by 2030 and 11-15% by 2035, relative to 2025 levels. Mr Guterres said: “Overshoot is not surrender. “We can still keep it as small and as short as possible – and bring temperatures back below 1.5C by the end of the century.”

Current policies and projections

With present policies worldwide, UNEP projects warming could hit 2.8C this century and keep climbing afterwards. Should every NDC be delivered and comparable efforts sustained, the agency found warming would be capped at 2.6C. Both figures exceed last year's UNEP projections, which the experts put down to the United States' withdrawal from the Paris Agreement and revised estimates of historical emissions. Fresh NDCs submitted since last year's report have made a negligible difference to these projections, it added. Even under the most optimistic scenario, in which all NDCs plus extra net-zero targets are met, global warming would be limited only to 2.1C this century. The report noted that progress in renewable energy and climate policy has produced genuine emission cuts across countries and sectors since the Paris Agreement was adopted, with total energy supply from coal and oil growing more slowly than forecast. Still, it cautioned that an enormous global scale-up is needed to get on track for the Paris Agreement's goals — and that opportunities to speed up action are greater than ever. Inger Andersen, UNEP's executive director, said: “Every additional fraction of a degree and additional year of warming above 1.5C increases climate impacts and risks, such as the deadly floods, heatwaves and wildfires that have plagued many nations this year. “We must pull out all the stops to minimise peak warming and return to 1.5C by the end of the century. This is possible. “We have a wealth of success stories showing that emissions can be cut quickly. “It is now up to nations to urgently put in place policies that spark fast, deep and sustained emissions reductions, and put the world on track for a more stable climate and more stable economies and societies.”