NAIROBI, Kenya - Pope Francis warned Thursday that it would be "catastrophic" for world leaders to let special-interest groups get in the way of a global agreement to curb fossil fuel emissions as he brought his environmental message to the heart of Africa on the eve of crucial climate change talks in Paris.

Francis issued the pointed warning in a speech to the U.N.'s regional office here after celebrating his first public Mass on the continent.

The joyous, rain-soaked ceremony before 300,000 faithful saw the Argentine pope being serenaded by ululating Swahili singers, swaying nuns, Maasai tribesmen, and dancing children dressed in the colors of Kenya's flag.

Francis has made ecological concerns a hallmark of his nearly three-year-old papacy, issuing a landmark encyclical earlier this year that paired the need to care for the environment with the need to care for humanity's most vulnerable.

Francis argues the two are interconnected since the poor often suffer the most from the effects of global warming, and are largely excluded from today's fossil-fuel based global economy that is heating up the planet.

On Thursday, Francis repeated that message but took particular aim at those who reject the science behind global warming. In the United States, that includes some Republican presidential candidates and lawmakers, who have opposed steps President Obama has taken on his own to cut greenhouse gas emissions.

"It would be sad, and dare I say even catastrophic, were special interests to prevail over the common good and lead to manipulating information in order to protect their own plans and interests," Francis said.

He didn't elaborate, but in the United States at least, there has been a well-funded campaign that rejects the findings of 97 percent of climate scientists that global warming is likely man-made.

Politicians have cited these claims in their arguments that emissions cuts will hurt the economy.

Francis' message was praised by NASA historian Erik Conway, who cowrote the 2010 book Merchants of Doubt, which detailed the attempts by far-right institutions and like-minded scientists to discredit the science behind global warming and spread confusion in the public.

Conway said it was difficult to determine today how much money is still being directed into climate change denial since much if it goes through foundations.

Francis, who has said global warming is "mainly" man-made, said the world was faced with a stark choice in Paris: either improve or destroy the environment.

He said he hoped the Paris talks would approve a "transformational" agreement to fight poverty and protect the environment by developing a new energy system that depends on minimal fossil fuel use.

His speech followed a similarly emphatic one before the U.N. General Assembly in New York in September, and in various speeches on his travels to South America and Asia.