LONDON (Reuters) - Greenhouse gas emissions in 2020 could be between 8 billion and 13 billion metric tonnes (14.33 billion tons) above what is needed to limit global warming to two degrees Celsius, a United Nations' Environment Program (UNEP) report showed on Wednesday.
The annual report, prepared by UNEP and the European Climate Foundation, studied a range of estimates to assess whether current pledges for emissions cuts are enough to limit the worst effects of climate change.
It found the gap between countries' emissions cut pledges and what is needed to stay under what scientists say is the limit to avoid devastating effects from global warming has widened since last year's estimate of 6-11 billion tonnes due to higher-than-expected economic growth and other new data.
The World Bank warned this week that the world is likely to warm by 3-4 degrees by the end of the century and extreme weather will become the "new normal", affecting every region in the world.
Scientists say emissions will have to peak before 2020 and fall to around 44 billion tonnes (gigatonnes) by 2020 to have a good chance of limiting temperature rise to below 2 degrees.
Based on 2010 data, global emissions are estimated around 50 billion tonnes of carbon dioxide equivalent (CO2e) - 20 percent higher than 2000 emissions and 14 percent above the level needed in 2020 to stay under 2 degrees, UNEP said.
"If no swift action is taken by nations emissions are likely to be at 58 gigatonnes in eight years' time," the report said.
"Even if the most ambitious level of pledges and commitments were implemented by all countries and under the strictest set of rules, there will now be a gap of 8 billion tonnes of CO2e by 2020," the report added.
TECHNICALLY FEASIBLE TO CLOSE EMISSIONS GAP
In 2010, countries agreed to limit temperature rise to 2 degrees Celsius above pre-industrial levels but many countries have failed to enact emissions cuts to back up their promises.
U.N. scenarios indicate that cuts of 25 to 40 percent are needed to limit temperature rise.
Delegates from over 190 countries will meet in Doha, Qatar, next week for a U.N. conference to work on emissions cuts under a new climate pact which will only come into force in 2020.
If the necessary emissions cuts are delayed, costs could be at least 10 to 15 percent higher after 2020, the UNEP warned.
Estimates vary on the cost of inaction on climate change but it is projected to reach trillions of dollars.
If current emissions pledges are increased, more ambitious cuts are brought to the table and stricter accounting rules adopted, it is still technically feasible to close the emissions gap but swift action was needed, UNEP said.
Emissions could be reduced by around 17 billion tonnes from the building, power generation and transport sectors by 2020.
"Yet the sobering fact remains that a transition to a low- carbon, inclusive green economy is happening far too slowly and the opportunity for meeting the 44 billion metric tonne target is narrowing annually," said Achim Steiner, UNEP Executive Director and U.N. Under-Secretary General.
In response to the report, U.N. climate chief Christiana Figueres said that although time was running out, technical and policy tools were still available to allow the world to stay below 2 degrees.
"Governments meeting in Doha now need to urgently implement existing decisions which will allow for a swifter transition towards a low-carbon and resilient world," she said.
Environmental campaign group Greenpeace said coal use has caused over two thirds of the rise in CO2 emissions and that governments must speed up the deployment of clean energy.
The UNEP report involved 55 scientists from 22 countries.
(Editing by Keiron Henderson and James Jukwey)