Leaders of the Group of 20 major economies committed to the key Paris Agreement goal of limiting global warming to 1.5 degrees Celsius above pre-industrial levels.
G20 leaders have committed to the key goal of limiting global warming to 1.5 degrees Celsius, but campaigners slammed a "lack of ambition" as make-or-break UN climate talks opened in Glasgow.
In a statement on Sunday, G20 leaders reaffirmed their support for the Paris agreement goals of keeping "the global average temperature increase well below 2 degrees and to pursue efforts to limit it to 1.5 degrees above pre-industrial levels".
"We're proud of these results but we must remember that it's only the start," said Italian Prime Minister Mario Draghi, host of the talks.
Following a two-day meeting in Rome, the Group of 20 major economies agreed that keeping that goal would require "meaningful and effective actions", according to the final summit statement.
Keep 1.5C within reach
The goal had initially been raised in the landmark 2015 Paris Agreement.
But experts say meeting the 1.5 degree target means slashing global emissions nearly in half by 2030 and to "net-zero" by 2050, and the G20 set no firm date, speaking only of reaching the goal of net zero "by or around mid century".
The leaders, whose nations between them emit nearly 80 percent of carbon emissions, also promised action on coal, but failed to set a clear target on another key goal, to reach "net zero" emissions.
However, they did agree to end funding for new unabated coal plants abroad — those whose emissions have not gone through any filtering process — by the end of 2021.
Earlier, the COP26 climate talks opened in Scotland with a warning by summit president Alok Sharma that they were the "last, best hope" to keep the goal of limiting global warming to 1.5 Celsius above pre-industrial levels.
Environmental campaign group Greenpeace slammed the final statement as "weak, lacking both ambition and vision", saying G20 leaders "failed to meet the moment".
"If the G20 was a dress rehearsal for COP26, then world leaders fluffed their lines," said Executive Director Jennifer Morgan.
British Prime Minister Boris Johnson, the host of the COP26 summit also said the pledge from world leaders in Rome was "not enough", and warned of the dire consequences for the planet.
"If Glasgow fails, the whole thing fails," he told reporters, saying the G20 commitments were "drops in a rapidly warming ocean".
UN Secretary General Antonio Guterres also expressed disappointment at the outcome of the G20 summit, saying he left Rome "with my hopes unfulfilled — but at least they are not buried".