The agreement by the Group of Eight industrialized economies, which includes Great Britain, The United States, Japan, Germany, France, Italy, Canada and Russia was struck during the G-8 summit in northern Japan.

The goal must be compatible with "economic growth and energy security," the leaders said in a statement.

They also said it must be done with cooperation from all major economies, including China and India.

However critics argued that the 50 percent reduction target was insufficient, and have called for ambitious midterm targets for countries to cut emissions by 2020.

Unless the G8 leaders agree to immediate action and medium-term targets for reducing their greenhouse gas emissions by 2020, any long-term promises will be unattainable, international agency Oxfam affirmed today in Japan. The agency also called for dramatic increases in funding for developing countries to adapt to climate change, far beyond those contemplated in the new G8 Climate Investment Funds.

"For the millions of poor people already living with the disastrous consequences of climate change, this G8 is a significant opportunity not to be missed," said Antonio Hill, Oxfam spokesperson. "We don’t need more haggling or finger-pointing. We need urgent action to ensure emissions peak in the next few years. Without it, decades of progress in the fight against poverty will be undone."

"At this rate, by 2050 the world will be cooked and the G-8 leaders will be long forgotten," Antonio Hill continued.