Canada's historic decision to withdraw from the Kyoto protocol provoked heavy criticism from China on Tuesday, with Beijing saying the move went against international efforts to combat climate change.
Canada on Monday became the first country to declare it was formally exiting the pact, a reversal that will save it billions of dollars in fines, and poured scorn on the landmark treaty for hampering attempts to tackle pollution.
The decision reflected the reality of Canada's rising greenhouse gas emissions.
The Kyoto protocol, adopted in 1997, is the only global treaty that sets down targeted curbs in global emissions, but those curbs apply only to rich countries, excluding the United States, which refused to ratify the accord.
"We are invoking Canada's legal right to formally withdraw from Kyoto," Environment Minister Peter Kent said after returning home from a marathon UN climate conference in South Africa, at which nations agreed to a new roadmap for worldwide action.
"Kyoto is not the path forward for a global solution to climate change," Kent said. "If anything, it's an impediment.
"A new agreement with legally binding commitments for all major emitters that allows us as a country to continue to generate jobs and economic growth represents the path forward."
But China, the world's largest carbon emitter, hit out at Canada, with foreign ministry spokesman Liu Weimin describing Ottawa's decision as being "against the efforts of the international community," and "regrettable."
"We hope Canada will face up to its responsibilities and obligations, honor its commitments and actively participate in relevant international cooperation against climate change," Liu told a regular media briefing in Beijing.
China has always insisted that as a developing country it should be exempt from binding obligations on emissions.
Japan, meanwhile, said Canada's withdrawal was "disappointing," and noted that it was "indispensable that each country makes efforts" on climate change.
"I hope Canada will address the issue in a forward-looking manner," Japan's Environment Minister Goshi Hosono told reporters.
Canada agreed under the Kyoto Protocol to reduce CO2 emissions to 6.0 percent below 1990 levels by 2012, but its emissions of the gasses blamed for damaging Earth's fragile climate system have instead increased sharply.
Saying the targets agreed to by a previous Liberal administration were unattainable, Conservative Prime Minister Stephen Harper's government last year unveiled its own measures aimed at curbing emissions, in line with US efforts.
Pulling out of Kyoto now allows Canada to avoid paying penalties of up to CAN$14 billion (US$13.6 billion) for missing its targets.
Kent also cited major impacts on Canada's economy that will be avoided by withdrawing from the treaty.
"Under Kyoto, Canada is facing radical and irresponsible choices if we're to avoid punishing multi-billion-dollar payments," Kent said, noting that Canada produces barely two percent of global emissions.
"To meet the targets under Kyoto for 2012 would be the equivalent of either removing every car, truck, ATV, tractor, ambulance, police car, and vehicle of every kind from Canadian roads or closing down the entire farming and agricultural sector and cutting heat to every home, office, hospital, factory, and building in Canada."
For Kyoto supporters, the anticipated Canadian pullout was expected to be a symbolic blow and badly damage a UN climate process already weakened by divisions.
Last week at the UN climate conference in Durban, South Africa, Kent had already said that Kyoto was "in the past" for Canada.
The conference on Sunday approved a roadmap towards an accord that for the first time will bring all major greenhouse-gas emitters under a single legal roof.
Kent said that in the meantime, Canada would continue to try to reduce its emissions under a domestic plan that calls for a 20 percent cut from 2006 levels by 2020, or as critics point out, a mere three percent from 1990 levels.
The latest data last year showed that Canadian carbon emissions were currently up more than 35 percent from 1990.
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