They will also call for any human-induced temperature rise to be held below 2 degrees Celsius, says BBC environment analyst Roger Harrabin.
But environmental campaigners believe key commitments will be scaled back.
News of the G8 plans came as ex-Prime Minister Tony Blair urged rich nations to hit short-term climate targets by ramping up existing clean technologies.
They should also paying poor countries to protect their forests, Mr Blair said.
However our correspondent said that environmental campaigners fear that the United States is blocking the short-term emissions targets which scientists say are needed for us to keep to that two degree mark.
"American officials have privately told BBC News they just can't cut emissions as fast as they know is required" he said.
'Sensible acceptance'
Mr Blair insisted that acting on climate change was "urgent" and that progress was being made in engaging governments of some of the world's largest economies.
There was "a general acceptance on the part of most sensible people that we have to deal with it," he said.
"We have an American administration committed to tackling climate change.
"We have a Chinese administration that's no longer saying you guys have created the problem - you solve it, but has immersed itself in this challenge."
But Mr Blair added that "practical policy making" was now needed if the fight against global warming was to be effective.
Technological solutions to climate change were "well within our grasp" he added, saying only political will was needed to implement them.
"This is now at the stage where it's been taken out of the hands of campaigners and into the hands of the people who are going to have to get the job done," he told the BBC.
However campaigners have questioned whether politicians will get the job done, especially the global economic downturn.
'Universal acceptance'
Mr Blair's comments came in a report published ahead of Major Economies Forum, being held in Italy this week.
The document sets out seven policies to cut carbon dioxide (CO2) emissions over the short and long term.
These include greater energy efficiency, an end to deforestation, using lower-carbon power sources and investing in technologies needed to reduce CO2 by between 50% and 85% by 2050.
In December, Copenhagen will host a United Nations climate change summit.
Mr Blair said, unlike previous events at Kyoto in 1997 and Gleneagles in 2005, there was now "almost universal" acceptance of the scientific evidence that climate change was a reality.
There was also a willingness from politicians to adopt ambitious CO2 reduction targets, if they were practical, he added.
Despite the financial restrictions placed on governments by the global recession, the cost of inaction was "far greater" Mr Blair said.
'Clean' energy
The report is published with the Climate Group - a charity which promotes how government, especially in cities, can move to low- carbon economies.
It said technologies which enable this offered the chance of "substantial job creation and growth".
Rising oil price could make switching to low-carbon technologies a cheaper option, it added.
The report said the technologies needed to meet emission reduction goals set for 2020 were "already proven, available now and the policies needed to implement them known".
Almost half the emission cuts could be reached by halting deforestation and the degradation of forests, the report said, something that would require developing nations to be given support from richer countries.
Other action called for included investment in alternative, "clean" energy sources such as wind and solar as well as carbon capture and storage, new generation nuclear plants and electric vehicles.
