UNITED NATIONS — Goals on reducing greenhouse gases announced by major industrialized nations are a step forward but not enough to forestall the disastrous effects of climate change by midcentury, U.N. officials said Monday.

Janos Pasztor, Secretary-General Ban Ki-moon's top climate adviser, said the goals, submitted to the U.N. as part of a voluntary plan to roll back emissions, make it highly unlikely the world can prevent temperatures from rising above the target set at the Copenhagen climate conference in December.

Fifty-five nations — including China, the United States and 27-member European Union — met a Jan. 31 deadline to submit pledges to the U.N. for cutting those emissions. Together they produce 78 percent of the world's greenhouse gases stemming from fossil fuel burning. The deadline had been set at the Copenhagen conference.

More such commitment letters were expected to continue trickling in over the next several days.

"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," Pasztor told the Associated Press.

The "two degrees" refers to the Copenhagen target of keeping the Earth's average temperature from rising two degrees Celsius (3.6 degrees Fahrenheit) above the levels that existed before nations began industrializing in the late 18th century. It would be no more than 1.3 degrees C (2.3 degrees F) above today's average temperatures.

"That is the bottom line, but you can look at it negatively and positively," Pasztor said. "The negative part is that it's not good enough. The positive side is that for the first time, we have a goal, a clear goal that we're all working toward. ... Before we would just talk."

The commitment letters, which largely reaffirm previous pledges, were intended to get an idea of how far the nations most responsible for global warming might be willing to go, toward a legally binding pact at the climate conference planned for Mexico City at the end of the year.

China has pledged to reduce its emissions growth — not make absolute cuts — by up to 45 percent from 2005 levels by 2020. India also pledged to reduce emissions growth by up to 25 percent from 2005 levels by 2020.

The United States stuck to President Barack Obama's pledge to cut its absolute carbon emissions by about 17 percent by 2020 below 2005 levels.

The European Union has pledged to cut its carbon emissions 20 percent below 1990 levels by 2020, and to cut 30 percent if other nations deepen their reductions.

The Copenhagen Accord, brokered by Obama and more than two dozen other world leaders, fell far short of the legally binding treaty sought from the two-week conference.

The accord, however, included collective commitments by developed countries to provide billions of dollars to help poor countries adapt to climate change. Nations also were encouraged to formally "associate" themselves with the accord after the conference, but no deadline for that action was set.

The U.N.'s climate chief, Yvo de Boer, said the pledges sent in by Jan. 31 should at least help to reinvigorate negotiations toward a stronger agreement on climate — a legally binding treaty. The hope is that such a treaty can be completed at the U.N. climate conference in Mexico City at the end of this year.

"The commitment to confront climate change at the highest level is beyond doubt," de Boer said. He said the pledges were "clear signals of willingness to move negotiations towards a successful conclusion."

Critics say the Copenhagen accord was a failure, with world leaders missing a crucial opportunity to commit to greenhouse gas cuts required to stave off projections extreme weather events.

Scientists believe global emissions must be cut in half by mid-century in order to avoid the melting of glaciers and icecaps, the flooding of low-lying coastal cities and islands, and worsening droughts in Africa and elsewhere.

Alden Meyer, policy director at the Union of Concerned Scientists, called the "political commitment" a breakthrough of sorts.

"This is the first time countries are committed to this goal, that's the good news," he said. "The bad news, of course, is the pledges that have been put on the table to date don't put us on track to meet that goal." (AP)