WASHINGTON — One question could dominate this week's gathering of the world's top economic powers in Italy: Will the United States and Europe act by themselves to cut emissions of the heat-trapping gases that are causing long-term global warming and will they be able to persuade fast-developing nations such as China and India to go along?
President Barack Obama will lead a gathering of nations called the Major Economies Forum, looking to forge a consensus for a global pact to stop global warming ahead of a climate meeting in December in Copenhagen, Denmark.
He'll arrive Wednesday in Italy reportedly prepared to embrace the broad goal of limiting global warming to an increase of 2 degrees Celsius — 3.6 degrees Fahrenheit — in the global average temperature since the dawn of the industrial age. Many scientists see 2 degrees C as a dangerous threshold that shouldn't be crossed.
Obama also will arrive at the Wednesday-Friday meeting in L'Aquila, Italy, armed with the tentative promise of U.S. action to cut its own emissions, a dramatic shift after years of opposition by the Bush administration. The House of Representatives has passed legislation that would put the first mandatory limits on U.S. emissions and reduce them if it becomes law.
However, the president faces a challenge winning Senate approval even for a proposal that environmentalists call watered down and Europeans consider short of what's needed. Even if the core group that's meeting in Italy — the world's eight top economic powers, called the G-8 — agrees to the goal of curbing global warming, it'll still find major countries such as China reluctant to sign on to specific emission cuts.
"It is premature to expect any major breakthroughs on contentious issues like targets for emissions reduction," said Sarah Ladislaw, an energy expert at the Center for Strategic and International Studies, a center-right research center in Washington.
Still, White House aides said that Obama hoped that the Major Economies Forum, a gathering of economic powers that produce roughly 80 percent of the world's greenhouse gas emissions, would build momentum toward an international pact in which all nations took action to fight global warming, though not all in the same way or on the same timetable.
"Obviously bolstered by the great progress in the House last week, the president will chair that meeting and press for continued progress on energy and climate," said Denis McDonough, the president's deputy national security adviser for strategic communications.
The first test could be reaching broad agreement on the goal of capping global warming at 2 degrees Celsius. Global temperatures already have risen about 1 degree C. Keeping them from rising more than 1 to 3 degrees C this century would require aggressively reducing greenhouse gases.
Although the magnitude of change is difficult to predict, scientists forecast that if the world takes the least aggressive approach to reducing emissions, the global average temperature will increase by another 2.5 to 6.5 degrees C (4.5 to 11.7 degrees Fahrenheit) by 2100.
German Chancellor Angela Merkel said last week that she expected the G-8 to endorse the 2-degree C goal and suggested that the United States will go along for the first time.
"We cannot do this without the United States," she said in Berlin of the fight against global warming. "That's why it will be important to have a clear acknowledgement of the 2-degree goal in the documents from the L'Aquila summit."
The European Union, which already has endorsed the 2-degree C cap as well as plans to cut its own emissions, wants the United States to go farther than the cuts that the U.S. House has approved. That bill would cut U.S. emissions by 17 percent from 2005 levels by 2020. The Europeans want a 20 percent reduction from the much lower levels of 1990.
Yet the Europeans realize that Obama will have a hard enough time enacting the House cuts.
"They know this is delicate, and I don't think they'll push too much on the public side, but I think they will privately push President Obama to make really strong commitments," said Heather Conley, the director of the Europe Program at the Center for Strategic and International Studies.
"They have to give President Obama some domestic space," she added.
A key political challenge at home is the price of regulating emissions from smokestacks and tailpipes. Another is the prospect that the United States might commit to an expensive plan to curb emissions while economic rivals such as China and India do not.
China hasn't been willing to commit to a target of emissions reductions, but it's been enacting policies that will reduce the amount that its emissions are increasing. China and other countries are looking to the G-8 for financial support for clean-energy technology and adapting to climate changes that already are happening.
"I don't know how many times they have to say no," said Ben Lieberman, a senior policy analyst on energy and the environment at the Heritage Foundation, a conservative policy-research center. "They're not willing to do to themselves what we're asking to do unilaterally to the U.S."
The Italy meetings also will include discussions of how to respond to Iran's disputed presidential election and North Korea's missile launches, as well as efforts to ease the worldwide recession and regulate business and finance.
While he's in Italy, Obama also will meet with Pope Benedict XVI, the spiritual leader of the world's Roman Catholics.
Renee Schoof contributed to this article.)
OBAMA'S MEETINGS IN ITALY:
Here's a reader's guide to the dizzying number of groups that President Barack Obama will meet with in Italy, with some leaders dropping in and some dropping out depending on the meeting:
G-8: This is the world's eight top economic powers: Canada, France, Germany, Italy, Japan, Russia, the United Kingdom and the United States.
G-8 plus 5: The top eight plus Brazil, China, India, Mexico and South Africa.
G-8 plus 5 plus 1: Add Egypt.
G-8 plus Africa: Add Algeria, Angola, Nigeria, Senegal and the African Union.
G-8 plus 3: Add the Netherlands, Spain and Turkey
Major Economies Forum: Australia, Brazil, Canada, China, Denmark, the European Union, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, South Africa, South Korea, the United Kingdom, the United States.
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