NEW YORK -- Washington's inaction on climate legislation is a "very serious hand brake" on world efforts to combat global warming, the U.N. climate chief said Thursday.
But Christiana Figueres said she believes the U.S. will eventually join the rest of the industrialized world in mandatory reductions of greenhouse gases.
"I don't think it's a permanent state of affairs that the world will be able to live with," she said of the failure of the U.S. Congress to cap emissions of carbon dioxide and other gases blamed for global warming.
Figueres, head of the U.N. climate treaty secretariat, met with Associated Press editors and reporters in New York as the National Research Council issued an authoritative report in Washington on "America's Climate Choices," urging the federal government to act to "substantially reduce greenhouse gas emissions."
Climate change, "very likely caused by human activities," is "one of the most important challenges facing the United States and the world today," said the 22-member expert panel.
Figueres, a Costa Rican environmental specialist appointed to the U.N. post last year, oversees the long-running global negotiations that thus far have failed to produce a new binding agreement on slashing greenhouse emissions, in good part because of American opposition.
The U.S., alone among industrial nations, rejects the existing agreement, the Kyoto Protocol, whose mandatory, relatively modest reductions expire next year. Washington says such mandates should apply to poorer but fast-developing nations, such as China and India, and not just to the developed world.
Although some Democrats in Congress oppose climate action, the main resistance comes from Republicans, many of whom reject scientific evidence on warming and climate change. The Republican Party takeover of the U.S. House this year rules out action for at least two years.
Figueres said she sees a "very remarkable dissonance" between the "political incapacity" in Washington and the United States' technological potential to lead the world toward a future of clean energy and less dependence on polluting fossil fuels.
"From an international point of view," she said, it "puts a very serious hand brake on the whole pace of negotiations."
Faced with these obstacles, the Obama administration for two years has promoted a voluntary approach to emissions reductions. But Figueres said international negotiators increasingly realize this unreliable "bottom-up" approach will fall far short of what's needed to keep temperatures from rising more than 2 degrees Celsius (3.6 degrees F) above preindustrial levels.
That's the level beyond which scientists predict severe damage from extreme weather events, droughts, floods, rising seas and other impacts of global warming.
Because of that realization, she said, she believes the annual U.N. climate conference, in Durban, South Africa, late this year, might produce movement toward an eventual legally binding agreement of "predictable" emissions reductions.
"The expectation is that the United States live up to its responsibility, to its historical responsibility" as the past single greatest source of greenhouse gases now filling the atmosphere, Figueres said.
Without emissions reductions, the U.N. network of climate scientists projects global average temperatures might rise as much as 6.4 degrees C (11.5 F) in this century. An authoritative scientific assessment issued May 3 forecast sea levels rising by 90 to 160 centimeters (35 to 63 inches) by 2100, as oceans expand from heat and from runoff of melted land ice.