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".
Well look at that. The poorest nations on the planet are working to save the planet, while in America we just voted in a guy who thinks that climate change is a Chinese hoax.
Once again the world moves forward, while America trips over its own feet.