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 said Friday.

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.