The 2015 Commonwealth Summit kicks off on Friday to a grand opening ceremony with Queen Elizabeth, followed by intense working sessions where world leaders will grapple with climate change.
As the clock ticks to a UN climate conference in Paris starting Monday, leaders including France's Francois Hollande, Britain's David Cameron and the UN's Ban Ki-moon will try to open the door to a landmark accord for taming greenhouse gases.
"We look towards Paris and an agreement that will determine the survival of our species and all those who share this precious planet with us," Britain's Prince Charles said in a speech in Malta on Thursday, as leaders arrived on the windswept island from four continents.
"We do not have the right to steal our children and grand-children's inheritance. We do have a responsibility to act now... and I'm sure that the Commonwealth will play a critical and leading part in this endeavour," the heir to the throne said.
Born out of the British empire, the Commonwealth of Nations brings together around a quarter of the world's countries and a third of its population. The 24th biennial summit is expected to focus on the issues of extremism and migration as well as the environment.
Prime ministers attending include Canada's new leader, Justin Trudeau, Pakistan's Nawaz Sharif and Pakalitha Mosisili from Lesotho.
The hope is that by finding common ground in Malta -- among countries which differ enormously in terms of culture, size, GDP and diplomatic muscle -- the COP21 talks in Paris can break through a logjam of connected and highly contentious issues.
Potential stumbling blocks in Paris abound, ranging from financing for climate-vulnerable countries to scrutiny of commitments to curb greenhouse gases and even the legal status of the planned accord.
The last attempt to get a global climate deal -- at the ill-tempered 2009 Copenhagen summit -- foundered upon divisions between rich and poor nations.
'Fervent hope' for a deal
Hollande, as president of the conference's host country, is expected to make an impassioned plea at the Commonwealth summit later Friday, before diplomatic toils continue on the sidelines of a banquet hosted by Queen Elizabeth.
The objective in Paris is to forge a post-2020 deal that will prevent global warming from breaching two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial levels.
"It is the fervent hope of countless concerned people around the world that global leaders... agree to an ambitious long-term goal for the rapid reduction of carbon emissions," Charles said, adding that the fate facing humankind should the plan fail "utterly beggars belief".
Countries most at risk -- including low-lying small island states and poor nations in Africa, many of whom are Commonwealth members -- have called for capping warming to 1.5 C, saying anything less would result in catastrophic impacts.
The Commonwealth's Business Forum warned it was not just vulnerable nations that would pay the price of inaction, and companies globally would have to react to survive.
One billion more people are expected on the planet by 2025, sparking a 35-percent increase in global food demand and a 50-percent increase in energy demand, while carbon emissions would have to be cut by six percent to stay within 2.0 degrees, it said.
Prince Charles insisted an accord would mean little if the private sector could not be persuaded to get behind the climate change fight.
The sentiment was echoed by Sherard Cowper-Coles, senior adviser to the chairman of HSBC -- one of the companies brought in to explain the potential financial gains to be made from businesses getting into bed with the green economy.
He said Thursday that what companies needed from the Commonwealth talks and the Paris summit was "a signal that governments believe private finance is absolutely essential".
"There are some in the community who believe it should all be done with public money. If you believe that, you are condemning humanity to a very bleak future."