L'AQUILA, Italy — The Canadian government refused Thursday to adjust its battle plan against global warming even though its objectives fall short of the new commitment from the G8 group of industrialized countries to slash greenhouse gas emissions by mid-century.

That made Canada one of the targets for criticism after President Barack Obama failed Thursday to obtain clear commitments from emerging industrial powerhouses like China and India to commit to specific targets for greenhouse gas emission reductions.

Critics, from United Nations Secretary General Ban Ki-moon to environmental lobby groups, said developed countries didn't show adequate leadership at the G8 summit here despite a widespread recognition that they bear more responsibility than poorer countries for fighting climate change.

But Prime Minister Stephen Harper and his environment minister, Jim Prentice, said Canada is doing all it can in advance of the UN-sponsored negotiations in Copenhagen in December aimed at a new climate treaty to replace the Kyoto Protocol, the 1997 treaty that will expire in 2012.

Canada joined its partners in the G8 group of industrialized countries — the U.S., Russia, Japan, Great Britain, France, Germany and Italy — in supporting an overall 80 per cent cut in emissions by mid-century.

But Prentice said the Canadian government won't budge from its vow to reduce emissions by 60 to 70 per cent by 2050.

"This is a realistic target (given) the climate we have, the industrial base we have, our population growth," Prentice told reporters.

Harper said Canada's reduction plan is in line with the Obama administration's.

"We have an integrated economy," he said. "If we had regulations that are not similar to the United States, we will simply have a loss of business and production to the United States."

Russia, like Canada described recently as one of the G8's "bad boys" on climate change by an environmental group, also said it wouldn't abide by the G8 pledge.

A coalition of Canadian environmental groups said the Harper government's targets fall far short of its global responsibility as one of the world's wealthiest nations.

"Canada's current 2020 target, which is equivalent to just three per cent below 1990 levels, falls far short of the emission cuts needed to avoid dangerous climate change," Climate Action Network Canada said in a statement.

Obama led a meeting of 16 major greenhouse-gas emitting countries plus representatives of the European Union on Thursday in a bid to get a broader commitment in support of overall global reductions of 50 per cent by 2050.

The group, called the Major Economies Forum, agreed with the G8 that an average global temperature increase two degrees Celsius above pre-industrial age levels would be catastrophic. The planet is now 0.8 degrees above pre-industrial levels.

However, they failed to accept specific targets due to foot-dragging from India and China, countries that have complained that their richer counterparts haven't set sufficiently aggressive medium-term targets for 2020.

The developing world also wants a multibillion-dollar support package to help their economies adjust.

The UN's Ban issued a statement Thursday saying he's disappointed with the results this week and is, therefore, calling for a global summit in September to try to build momentum heading into the critical Copenhagen talks in December.

"The time for delays and half-measures is over," he said.

He said political leadership is needed "to protect people and the planet from one of the most serious challenges ever to confront humanity."

Brazil also questioned the G8's leadership, saying the 2050 target was "not credible" unless it was accompanied by targets for 2020 — the year when the UN says emissions must peak and start to move downward.

The Canadian government, meanwhile, announced it will increase food security funding by $600 million over three years, increasing Canada's total commitment to $1.2 billion.

The money, from development aid funds previously budgeted by the Conservative government, is to support Obama's bid to come up with $17.4 billion over three years to improve sustainable agricultural practices and emergency food assistance.

Oxfam Canada president Robert Fox said Canada should have done more as part of western efforts to deal with one billion malnourished people in the world, up 11 per cent from a year ago.

Canada also announced it will join a group of countries to create the Global Carbon Capture and Storage Institute, a body that will help advance the costly new technology aimed at letting companies capture and store carbon underground.

Harper, meanwhile, once again drew chuckles from the world's top leaders for showing up late for the so-called "family photo" in advance of Thursday's meeting.

Harper, who caused a stir at the G20 in London in April for missing the group photo, was the last to arrive Thursday for a formal photo in advance of a working lunch to discuss issues like climate change and the economy.

"Harper, Harper!" one of the leaders shouted after noticing that Canada's prime minister still hadn't shown up.

Harper kept his colleagues waiting almost two minutes after Obama, the second-last to arrive, before showing up.

The international media seized on reports at the April G20 summit that Harper missed the photo due to an ill-timed bathroom break. The Prime Minister's Office said later that Harper was actually being briefed and wasn't in the bathroom.