LONDON, Oct 21 (Reuters) - Global warming is now projected to exceed previous estimates, with even the most optimistic scenario seeing average temperatures rise to 1.7-1.8 degrees Celsius above pre-industrial levels by mid-century, a UN report showed on Wednesday.
Despite a rapid expansion of renewable energy and climate policies that are reducing emissions in many countries, the report said "urgent and stringent" cuts were still needed to achieve that best-case outcome.
The UN Environment Programme's report said greenhouse gas emissions would need to fall 18% from 2025 levels by 2030, 45% by 2035 and 69% by 2040. Current national plans would cut emissions by only 5-8% by 2030 and 11-15% by 2035.
The report projected global warming of 2.8 Celsius by 2100 under current policies, or 2.6 C if countries fully implement existing climate pledges. Both estimates are higher than last year's projections, reflecting the US withdrawal from the Paris Agreement and revised assessments of historical emissions.
As countries prepare for the next round of climate talks in Turkey, COP31, UN Secretary-General António Guterres said it was crucial not to give up on efforts to rein in the emissions that are fuelling floods, fires and other natural disasters.
"Overshoot is not surrender. We can still keep it as small and as short as possible – and bring temperatures back below 1.5 degrees by the end of the century," he said.
Under the 2015 Paris Agreement, countries agreed to try to keep the average temperature increase at well below 2 degrees and ideally 1.5 C.
As limiting warming to 1.5 C with no or limited overshoot was no longer considered possible, the UN Environment Programme said its new "lowest possible" overshoot scenario gives roughly a 50% chance that temperatures could return to 1.5 C or below by 2100.
The report said climate plans submitted since last year had made virtually no difference to future warming projections, and that returning to 1.5 C would depend on large-scale carbon removal, the feasibility of which was uncertain.
(Reporting by Simon JessopEditing by Ros Russell)
