Leaders from the Group of Eight (G8) major industrialized countries agreed on Wednesday to limit global warming to within two degrees Celsius above pre-industrial levels, but lowered their target of halving greenhouse gas emissions by 2050.

"We recognize the broad scientific view that the increase in global average temperature above pre-industrial levels ought not to exceed two degrees Celsius," the leaders said in a declaration concluding their first-day summit talks in the central Italian town of L'Aquila.

Scientists had warned that there would be serious climate consequences if the world temperature rise exceeds the threshold of two degrees Celsius.

The United States has been reluctant to accept the two-degree limit, a goal strongly supported by the European Union (EU). This is the first time the G8 leaders accepted this political goal in the global fight against climate change.

The G8 leaders also said they are ready to attain the goal of reducing global emissions of greenhouse gases by at least 50 percent by 2050, together with others, but without specifying the baseline.

"We reiterate our willingness to share with all countries the goal of achieving at least a 50 percent reduction of global emissions by 2050, recognizing that this implies that global emissions need to peak as soon as possible and decline thereafter," they said.

The EU has been pushing for a reduction by half from the base year of 1990, while the United States wants to use as the reference the emission level of 2005, which is higher than that of 1990.

It had been expected that Washington would make a concession, but the declaration left the issue open.

As part of their long-term effort, the G8 leaders also supported the goal of developed countries reducing greenhouse gas emissions in aggregate by 80 percent or more by 2050. However, they said that the reduction should be comparable to 1990 or more recent years.

In a subtle wording, the G8 leaders said "they will undertake robust aggregate and individual mid-term reductions, taking into account that baselines may vary and that efforts need to be comparable."

The mid-term reduction usually refers to the target by 2020, which would mean a more imminent burden for the G8 countries.

The joint stance on climate change would be submitted at a meeting on Thursday, which is extended to include the five emerging economies of Brazil, China, India, Mexico and South Africa.

Italian Prime Minister Silvio Berlusconi, the host, signaled a showdown with the emerging economies.

"Europe and the United States are in favor of cutting carbon dioxide emissions and will adopt a united stance vis-a-vis the emerging economies with a view to arriving at a pledge into which everyone must enter," he told reporters after the first-day meeting.

While being vague about targets for themselves, the G8 leaders took a tougher position against emerging economies, adding doubt to what can be achieved on Thursday.

"Major emerging economies need to undertake quantifiable actions to collectively reduce emissions significantly below business-as-usual by a specified year," the declaration said.

Meanwhile, leaders of the five emerging economies, also called the Group of Five (G5), met separately on Wednesday.

In a joint statement, they urged developed countries to commit themselves to ambitious and comparable quantified emission reduction targets by reducing their emissions in aggregate by at least 40 percent below their 1990 levels by 2020.

Reaffirming the principles of common but differentiated responsibilities and respective capabilities, the G5 leaders prodded the G8 countries to "provide measurable, reportable and verifiable technology, financing and capacity building to support and enable developing countries to take nationally appropriate mitigation actions in the context of sustainable development."

The G8 summit in Italy is considered crucial to a new global pact on climate change to replace the current Kyoto Protocol, which expires in 2012.

Governments are scheduled to meet in Copenhagen, Denmark, at the end of this year, hoping to wrap up the negotiations.

(Xinhua News Agency July 9, 2009)