Queen Elizabeth II got a carnival welcome in Port of Spain
Commonwealth leaders have backed a multi-billion-dollar plan to help developing nations to deal with climate change and cut greenhouse gases.
The fund, proposed by UK and French leaders at the Commonwealth summit on Friday, would start next year and build to $10bn annually by 2012.
Many Commonwealth members are island states threatened by rising sea levels.
Leaders also called for the strongest possible outcome at next month's climate change summit in Copenhagen.
They unanimously agreed to seek a legally binding international agreement, but accepted that "a full legally binding outcome" might have to wait to 2010.
James Robbins, BBC News diplomatic correspondent
Did the Commonwealth give a lead to the world on climate change, as the Queen urged when she opened this summit? The Commonwealth Climate Declaration does emphasise that "an internationally binding agreement is essential" but then concedes in the next sentence that "a full legally binding outcome" will have to wait until 2010.
That doesn't mean the Commonwealth has failed. The wording looks cautious but realistic. It is the breakdown in global negotiations which threatens to sink a strong deal.
There does seem to have been some meeting of minds at the Commonwealth on the global fund to distribute money from rich countries to the developing countries to help them adapt and pay for low-carbon alternatives.
Poorer countries can start to see the money now, with the promise of payouts starting soon after a global treaty is agreed.
That's a very direct incentive for the developing world.
Commonwealth leaders "welcomed the initiative to establish, as part of a comprehensive agreement, a Copenhagen Launch Fund starting in 2010 and building to a level of resources of $10 billion annually by 2012," a statement in Trinidad on Saturday said.
UK Foreign Secretary David Miliband said the declaration sent a clear political message.
"The Commonwealth is showing that you can find some common ground amidst countries that are very different, large and small, rich and poor, and that climate change is an issue that affects us all, and that the world needs to show the sort of resolution that we've seen here over the past 24 hours," he said.
It added that "fast start funding" for adaptation should be focused on the most vulnerable countries.
"We also recognise the need for further, specified and comparable funding streams, to assist the poorest and most vulnerable countries, to cope with, and adapt to the adverse impacts of climate change. We recognise that funding will be scaled up beyond 2012."
UK Prime Minister Gordon Brown said half the $10bn fund should go towards helping developing nations reduce their greenhouse gas emissions and the other half towards helping them adapt to climate change.
The first cash would be made available next year, he said, before any emissions deal could take effect.
Kevin Rudd stressed it was "time for action"
Commonwealth leaders met days after pledges by the US and China to limit their greenhouse gas emissions, amid concerns that December's Copenhagen meeting on climate change could fail to agree substantial cuts.
Australian Prime Minister Kevin Rudd told a news conference in Trinidad on Saturday that the Commonwealth - representing a third of the world's population - believed "the time for action on climate change has come."
"The clock is ticking to Copenhagen. We've achieved one further step, significant step forward with this communique and we believe the political goodwill and resolve exists to secure a comprehensive agreement at Copenhagen."
India's Prime Minister Manmohan Singh said that when his country unveils its first targets for carbon emission cuts they would be "ambitious".
But he also stressed that India's offer would be conditional on other countries sharing the burden.
That neatly illustrates the greatest threat to a global deal, says the BBC's James Robbins.
Many countries will only make binding concessions if every other nation also gives ground, our correspondent says.
Speaking earlier at the summit, UN Secretary General Ban Ki-moon said he believed an agreement was in sight, with recent moves by some countries a positive step to cutting emissions.
The head of the UN's panel of climate experts, Rajendra Pachauri, said he was now very optimistic a deal could be reached in Copenhagen.
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