Representatives from 47 of the world's most disadvantaged nations have pledged to generate all their future energy needs from renewables.
Members of the Climate Vulnerable Forum issued their statement on the last day of the Marrakech climate conference.
Bangladesh, Ethiopia, and Haiti, among others, say they will update their national plans on cutting carbon before 2020.
Delegates here welcomed the move, saying it was "inspirational".
These two weeks of negotiations have been overshadowed to an extent by reaction to the election of Donald Trump to the US presidency.
But in an effort to show that even the world's poorest countries are committed to dealing with global warming, the Climate Vulnerable Forum (CVF) members have issued a promise to fully green their economies between 2030 and 2050.
Termed the Marrakech Vision, the plan promises that the 47 members will: "strive to meet 100% domestic renewable energy production as rapidly as possible, while working to end energy poverty and protect water and food security, taking into consideration national circumstances".
The countries involved are keen supporters of keeping the global temperature rise this century under 1.5C, a target agreed during negotiations in Paris last year.
"We are pioneering the transformation towards 100% renewable energy, but we want other countries to follow in our footsteps in order to evade catastrophic impacts we are experiencing through hurricanes, flooding and droughts," said Mr Mattlan Zackhras, a minister from the Marshall Islands.
The CVF countries also pledged to update their national climate-cutting plans before 2020 and to develop long-term plans as soon as possible.
There was also a hint of impatience among CVF members with the progress being made by richer countries.
"We don't know what countries are still waiting for to move towards net carbon neutrality and 100% renewable energy," said Edgar Gutierrez, Costa Rica's minister for the environment.
"All parties should start the transition, otherwise we will all suffer."
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