L'AQUILA, Italy - Targeting global warming, President Obama and other leaders of the world's richest industrial countries pledged yesterday to seek dramatic cuts in greenhouse-gas emissions by 2050 to slow dangerous climate change.

Setting a marker for success, they agreed for the first time that worldwide temperatures must not rise more than a few degrees.

However, their goals are nonbinding, and it's far from clear they will be met. The wealthy nations failed to persuade the leaders of big developing countries to promise to cut their own fast-spreading pollution, unable to overcome arguments that the well-established industrial giants aren't doing enough in the short term.

Obama and his counterparts from the other wealthy Group of Eight nations agreed that global temperatures should be kept from rising more than 2 degrees Celsius, or 3.6 degrees Fahrenheit, in the fight against weather changes caused by mankind.

The results left some Western leaders cheering. British Prime Minister Gordon Brown called the group's statement a "historic agreement." German Chancellor Angela Merkel said it was "a clear step forward."

But environmental groups said the effort fell far short in its bid to cut carbon emissions, which come mainly from energy production and trap heat in the atmosphere.

Still, climate-change experts said the measure on trying to limit temperature increases - with agreement by both the G-8 and a 17-member group of industrialized and developing nations meeting in Italy this week - was an important step.

An increase up to the limit the leaders set would not eliminate the risk of runaway climate change but would reduce it, experts said. Even a slight increase in average temperatures could wreak havoc on farmers around the globe, as seasons shift, crops fail, and storms and droughts ravage fields.

"After a long struggle, all of the G-8 nations have finally accepted the 2-degree goal," Merkel said.

The United States and other G-8 nations set a goal of reducing their greenhouse gas emissions 80 percent or more by 2050. That's part of a plan to have all such gases, from rich and poor nations alike, fall by 50 percent globally by that year.

But developing countries feel the better-established nations aren't doing enough in the shorter term. They also worry that major reduction commitments on their parts, even if below the 80 percent target of rich nations, would hamper economic growth in China, India, Mexico, Brazil, and many other non-G-8 countries.

As for the target for limiting global temperatures, a summit statement said it reflected a "broad scientific view."

Before the summit, the United States had resisted embracing the target because it implied a commitment to dramatically change the way the world generates electricity, fuels its cars. and builds its houses.

Environmentalists welcomed the shift in U.S. policy but criticized the G-8's failure to agree on more immediate goals for the industrial countries. The long-term ambition "is too far off to matter - poor people are being hit today," said Antonio Hill of the nonprofit group Oxfam International.

The G-8 leaders also addressed the global recession and agreed that economic conditions were still too shaky to begin rolling back massive fiscal-stimulus plans.

A statement said leaders "note some signs of stabilization," but it stressed the difficult outlook instead of counter-concerns over debt and high spending.

The leaders did commit to preparing exit strategies from the "unprecedented and concerted action" that has been taken to boost growth through government spending, low interest rates, and expansive monetary policy. Germany, worried about running up crippling debt, has pressed for spending restraint, but other major economies including Britain, Japan, and the United States won't rule out the need to pump in more money.

The leaders gathered yesterday in the earthquake-devastated central Italian city of L'Aquila, many arriving in electric cars. They were welcomed by their host, Italian Premier Silvio Berlusconi. Over a long working dinner, they discussed world security issues that included Iran and North Korea.

They emerged with a joint statement deploring government-backed violence and media restrictions in the aftermath of Iran's disputed election last month. The condemnation and concern were a far cry from the calls by some for something tougher, such as sanctions against Tehran or other action.

Obama also announced at the dinner that he would host a nuclear-security summit early next March in Washington. About two dozen nations are expected to attend, to focus on nuclear terrorism, the black-market trade in nuclear materials, and the detection and interception of materials in transit, Obama adviser Mark Lippert said.

Activists Scale Smokestacks

Environmental protesters broke into power stations across Italy

and shed their clothes in downtown Rome yesterday.

Dozens of activists scaled smokestacks and occupied four Italian coal-fired power plants, hanging banners that called on the Group of Eight summit in central Italy to take the lead in fighting climate change, Greenpeace said.

Italian energy giant Enel, which owns three of the plants, said production had not been disrupted. Employees at two

of the plants staged counterdemonstrations.

In Rome, activists from the charity group Oxfam International put on masks of world leaders and dressed up as chefs, stirring a mock Earth in a pot representing the planet's rising temperature.

On the Spanish Steps, activists stripped half-naked in front of tourists and unfurled

a banner calling on leaders to "keep climate cool." Police briefly detained two women,

a French citizen and

an American, as well as a Greek man.

- AP