* Two degree limit prevents most serious impact
* Business-as-usual would be up to 5 degrees
* U.N. to issue progress report by November
By Barbara Lewis
BRUSSELS, Sept 15 (Reuters) - National promises to cut emissions as part of preparations for a United Nations summit at the end of the year would cap global warming at the unacceptably high level of 3 degrees Celsius, the U.N.'s climate boss said on Tuesday.
The talks in Paris, starting on Nov. 30, will seek a global deal to curb warming, which scientists say needs to be limited to 2 degrees Celsius (3.6 degrees Fahrenheit) to avoid the most devastating consequences in the form of droughts and rising sea levels.
U.N. Executive Secretary Christiana Figueres said so far 62 nations had submitted promises, covering around 70 percent of global emissions.
The United Nations has said it will add up the pledges by the start of October and issue a report by Nov. 1.
But Figueres said it was already a good "guestimate" that the pledges, known in U.N. language as INDCs (Intended Nationally Determined Contributions) would equate to 3 degrees of warming compared with pre-industrial times.
Aware of the shadow cast by the 2009 Copenhagen summit, the last attempt to reach a global climate deal that ended in failure, EU officials and the U.N. stress Paris is a step, not the end result.
Figueres told reporters in Brussels she wanted it to be "pellucidly clear" that the INDCs were not the magic route to 2 degrees, set as a target by the Copenhagen Accord, from the current trajectory of 4-5 degrees.
"What the INDCs will do is mark a very substantial departure from business as usual," she said. "Is three degrees acceptable? No."
The U.N.'s plan to issue an INDC report by Nov. 1 is a departure from the early hopes of the most vulnerable nations and the European Union for a formal review to put pressure on the laggards before the Paris conference.
Although the EU is an acknowledged climate leader, its 28 members are wrangling over how ambitious they can afford to be.
The EU was the first major economic bloc to submit its INDC, saying it would cut domestic emissions by at 40 percent by 2030 versus 1990 levels.
The bloc's environment ministers meet on Friday to finalise their Paris negotiating position.
Poland, whose economy is heavily dependent on coal, the most polluting of the fossil fuels, wants assurances its international competitiveness will not be damaged by nations that do not follow the EU lead.
It is among those pushing for a clause on "a long-term vision of global carbon neutrality," EU diplomats said.
That, they said, could allow room for the EU to rely on emissions reductions made beyond Europe and through technology rather than relying on a domestic shift to lower carbon fuel. (additional reporting by Alister Doyle in Oslo)
Our Standards: The Thomson Reuters Trust Principles.