Carbon-cutting pledges from 146 nations for a universal climate rescue pact leave the "door open" to capping global warming below the danger threshold, the United Nations says.
But even if these 10-to-15 year plans are fulfilled, humanity will have used up three-quarters of its carbon "budget" by 2030 and must slash greenhouse gas output even more to avoid devastating climate impacts, the UN's Climate Change Secretariat warned on Friday (local time).
"An unprecedented world-wide effort is underway to combat climate change, building confidence that nations can cost-effectively meet their stated objective of keeping a global temperature rise to under 2degC," it said in an assessment of the country pledges.
At the same time, "much greater emissions reductions efforts ... will be required" to meet the 2degC target endorsed by the UN 195-nation climate body, it said.
The longer we wait, the harder and more expensive it will become to cut back the fossil fuel emissions that drive climate change.
The Secretariat's 66-page review comes exactly one month before the November 30 to December 11 Paris summit tasked with finalising a historic global pact.
As they stand, the pledges place the world on track for warming of some 2.7degC by 2100 – "by no means enough but a lot lower than the estimated four, five or more degrees of warming" that would have otherwise take place, said UN climate chief Christiana Figueres.
If countries commit in Paris to periodically revising ambition upward, the goal stays within reach, she added.