With less than three weeks remaining before negotiators gather in Copenhagen to hammer out a global response to climate change, a rapid-fire succession of countries are unveiling national plans that serve as opening bids for reining in heat-trapping emissions.
“The list of what is on the table is rather long,” said Yvo de Boer, executive secretary of the United Nations Framework Convention on Climate Change, the sponsor of the meeting, which runs from Dec. 7 to 18 in Copenhagen.
But, speaking at the United Nations headquarters on Thursday, he seized on the latest pledges to take aim at the United States, which has not yet played its hand.
“We now have offers of targets from all industrialized countries except the United States,” Mr. de Boer said. He emphasized that he was looking to the United States for “a numerical midterm target and commitment to financial support.”
“This is essential, and I believe this can be done,” he said.
In an interview, Todd Stern, the chief climate negotiator for the United States, said that the Obama administration was trying to decide whether to release a proposal in the coming days.
“What we are looking at is whether we feel that we can put down a number that would be provisional in effect, contingent on getting our legislation done,” he said. “Our inclination is to try to do that, but we want to be smart about it.”
He noted that bills pending in Congress involved cuts of around 17 percent in emissions by 2020, increasing to much deeper cuts by 2030.
The United States has the highest per capita emissions in the world. China has the largest emissions over all and has also refrained from setting a specific emissions reduction target, although as a developing country it would not be required to do so under the current outlines of the treaty that is being proposed.
If neither China nor the United States made a commitment, the national plans of lesser emitters would have little practical effect.
Although the United Nations no longer believes that the Copenhagen meeting can come up with a binding treaty to control emissions this year, the event is viewed as a crucial forum for the world’s nations to demonstrate a commitment to addressing global warming and its potential impact.
This week, South Korea said it would cut emissions by 30 percent from “business as usual” by 2020. Russia’s president, Dmitri A. Medvedev, said his country would try to reduce emissions by 25 percent by then, instead of 15 percent as announced earlier. Last week, Brazil promised reductions of about 40 percent below current projections by 2020.
The recent announcements are a mix of aspirations, good intentions and negotiating tactics. In most cases there is no certainty that the targets are politically or scientifically plausible. Still, they are a rough harbinger of the potential shape of future agreements and conflicts.
United Nations officials have said they hope that the richest industrialized nations will promise to reduce their emissions to meet negotiated individual targets. For developing nations, the hope is that they will commit to reducing their future emissions to levels below those that would accrue if they took no action. The poorest nations would get money and technological assistance to adapt to the consequences of climate change.
Many nations have based their new offers on that model. While some of the pledges are conditioned on reaching a binding international agreement, some countries, like South Korea, have said they will act whether the world did or did not.
South Korea, whose emissions nearly doubled from 1990 to 2005, said it would cut emissions by investing in energy-efficient buildings and transportation, developing new green industries and changing patterns of consumption.
“Our industry is really energy-intensive, so this is very ambitious,” Sang-Hyup Kim, South Korea’s secretary to the president for national future and vision, said in a phone interview from Seoul. He noted that the president and cabinet ministers had made the pledge in a building with the thermostat set low, and while wearing thermal underwear.
Last week, Brazil said it would offer to reduce its emissions by 38 to 42 percent from current projections for 2020. About half of that reduction would result from slowing deforestation in the Amazon. Forests are a crucial force in absorbing carbon dioxide.
The government described its action as a “political gesture” to show its good faith.
But it is in many ways easier for developing countries and so-called industrializing countries, like South Korea and Brazil, to put forth offers because they are under far less pressure to commit themselves formally under an agreement.
The industrialized countries — counted as those that were already industrialized when the United Nations Framework Convention on Climate Change was signed in 1992 — have the more concrete task of committing to specific reductions.
Despite the steady stream of new pledges, representatives of many of the world’s poorest countries have expressed frustration over a recent decision by world leaders to defer a binding agreement until next year.
“This is a major setback — we should not pretend otherwise,” Abdalmahmood Abdalhaleem Mohamad, Sudan’s United Nations representative, said Thursday, speaking for a coalition of developing nations.