Plans submitted by 140 nations to limit their greenhouse gases would go some way towards tackling climate change, but not enough to prevent the planet from warming by well over 2 degrees Celsius compared to pre-industrial times, experts say.
The plans by countries from Albania to Zimbabwe, led by top emitters China and the United States, were submitted by an informal United Nations deadline on Thursday as building blocks towards a climate accord that negotiators will try to clinch at a summit in Paris in December.
A Climate Action Tracker (CAT) by four European research groups projected the plans, if implemented, would limit average temperature rises to 2.7 degrees Celsius (4.9 Fahrenheit) above pre-industrial times by 2100, down from 3.1C (5.6F) estimated last December.
That is still clearly above the 2C (3.6F) level that governments have accepted as the threshold beyond which the Earth would face dangerous changes including more droughts, extinctions, floods and rising seas, which could swamp coastal regions and entire island nations.
"We're below three degrees for the first time," Bill Hare of Climate Analytics, which is part of CAT, said. "We're obviously far from where we need to be, but this is a signal that the process can work."
He said the main contributor was Beijing's plan, issued in June, to get emissions from burning coal, oil and natural gas to peak by around 2030.
A top priority for the Paris talks, six years after the failure of a previous summit in Copenhagen, will be to find ways to toughen the plans in order to meet the 2C target.
Together the plans cover almost 80 percent of global greenhouse gas emissions. The U.N. Climate Change Secretariat says it will add up them all up in coming weeks to estimate their effect in slowing climate change. It has privately told countries that they have a few days' leeway.
India, the biggest emitter yet to submit, plans to outline its plan for action on Friday to coincide with the birthday of independence leader Mahatma Gandhi.
Earlier this week, Climate Interactive, a not-for-profit group in Washington, using different assumptions from CAT, projected the national plans would curb temperature rises to 3.5C (6.3F), compared with 4.5C (8.1F) if no action was taken.