Christian Aid has warned that the impact of global warming will only worsen unless urgent action is taken on an international level.
The warning comes in response to the report published today by the UN's Intergovernmental Panel on Climate Change, which says scientists are 95% certain that humans are the "dominant cause" of global warming since the 1950s.
Dr Alison Doig, Christian Aid's Senior Climate Change Advisor, said that the economic and human cost of rising temperatures would be "huge".
She said countries and communities most at risk need support in preparing to cope with disaster and lessening the impact of extreme weather events.
"Scientific evidence confirms that manmade climate change is a reality and that without urgent action globally, the impacts will get worse. The time for debate is over, it is time to act," she said.
"The implications of melting ice caps and rising sea levels for people and economies around the world will be enormous, but it is the poorest and most vulnerable people who depend on the land and sea for their living who will be most affected."
Ms Doig called upon the UK to lead the way in loosening dependence on fossil fuels and investing in clean, renewable sources of energy.
"The report shows that there is time to put a halt to the continuing accumulation of carbon in our atmosphere, but that we need to move fast."
She added: "The science is clear, we have a moral duty to act and the risk of not doing so is too great. This is our opportunity to create the world we want to live in."