Cuts announced by the nations responsible for most of the world's greenhouse gas emissions will fall short of the level needed to limit disastrous climate change, the UN said today.
Janos Pasztor, top climate adviser to Secretary-General Ban Ki-moon, said the commitments, which largely reaffirm previous pledges, make it highly unlikely the world can meet the goal set at the Copenhagen climate conference of preventing temperatures from rising more than 2C above pre-industrial levels.
"It is likely, according to a number of analysts, that if we add up all those figures that were being discussed around Copenhagen, if they're all implemented, it will still be quite difficult to reach the two degrees," he said.
"That is the bottom line, but you can look at it negatively and positively. The negative part is that it's not good enough," he said. "The positive side is that for the first time, we have a goal, a clear goal that we're all working toward, and we know what the commitments are. ... Before we would just talk."
Mr Pasztor said some 50 nations - including China, the United States and the European Union - sent in their commitment letters by the February 1 deadline set at the Copenhagen climate conference in December.
More such letters were expected to continue trickling in over the next several days.
The goals submitted to the United Nations outline voluntary plans for reducing greenhouse gases from fossil fuel burning.
The commitment letters were intended to get an idea of how far the nations most responsible for global warming might be willing to go, in a step toward pushing for a legally binding pact later this year.
China has pledged to reduce the growth rate of its emissions - not make absolute cuts - by up to 45% from 2005 levels by 2020.
India also pledged to reduce the growth rate of its emissions by up to 25% from 2005 levels by 2020.
The United States stuck to President Barack Obama's pledge to cut its absolute carbon emissions by about 17% by 2020 below 2005 levels - setting a precedent for China and India to scrap the baseline 1990 emissions levels used in previous UN climate negotiations.
The European Union has pledged to cut its carbon emissions 20% below 1990 levels by 2020, and to cut 30% if other nations deepen their reductions.
The Copenhagen Accord fell far short of the legally binding treaty that had been the goal of the two-week conference, but included collective commitments by developed countries to provide billions of dollars in emergency funds to help poor countries adapt to climate change.
The three-page document was only "noted" by the full conference in Copenhagen after five countries blocked its formal adoption by consensus. UN officials now consider the accord a political tool for trying again to negotiate a binding climate treaty at the UN climate conference in Mexico City at the end of the year.
Critics say the accord was a failure, with world leaders missing a crucial opportunity to commit to greenhouse gas cuts required to stave off projections of dangerous melting of glaciers and ice-caps, flooding of low-lying coastal cities and island nations, more extreme weather events, drought in Africa and other continents, and the spread of diseases.
Scientists believe global emissions must be cut in half by mid-century.