"It would be sad, and I dare say even catastrophic, were particular interests to prevail over the common good and lead to manipulating information in order to protect their own plans and projects," the Pope said, urging nations to reach an agreement over curbing fossil fuel emissions.
He urged politicians to work together with the corporate and scientific worlds, and civil society leaders in finding solutions to stop environmental degradation.
No country, he said, "can act independently of a common responsibility. If we truly desire positive change, we have to humbly accept our interdependence."
The Pope spoke at the world headquarters of the United Nations Environment Programme in Nairobi, the Kenyan capital. The U.N. climate change conference opens next week.
But it was Francis' comments on the pillaging of African resources that drew a louder response from the crowd.
He said Africans cannot afford to remain silent on the illegal trade in precious stones and the poaching of elephants for ivory, which "fuels political instability, organized crime and terrorism."
The message reverberated with the crowd in what is arguably the Pope's most important speech during his first papal visit to Africa.
Climate change, like poverty, is a hallmark issue for Francis, the first leader at the Vatican who hails from the developing world. Other popes have visited Kenya, but the welcome was particularly warm for the populist Pope.
Humility, service to the poor
Francis arrived in Kenya on Wednesday and from there will travel to Uganda and the conflict-ravaged Central African Republic.
His time in Nairobi so far has highlighted two issues close to his heart: humility and service to the less fortunate.
During Mass earlier Thursday, he called on citizens to reach out to the downtrodden.
"I appeal in a special way to the young people of the nation," he said. " ... May you always be concerned for the needs of the poor and reject everything that leads to prejudice and discrimination, for these things, we know, are not of God."
Kenya declared the day a national public holiday as throngs of jubilant Catholics flocked to Nairobi to hear the Pope.
He drove past the crowd in his popemobile, waving to thousands who started lining the streets at dawn to catch a glimpse of him.
When he got to the University of Nairobi, the site of his first Mass in Africa, choirs and traditional dancers swayed to Swahili Christian music as they waited.
Music mixed with the sound of rain wafted across the field as crowds peeked from under multicolored umbrellas.
"I wish I was at that Mass now," said Jane Waceke, who was watching the Pope on television in the town of Nakuru.
"He's just what we needed, someone to lift Kenyans' spirits after the terrorist attacks we've had. I have a sense of peace and calm just watching him."
Francis' arrival in Nairobi was itself a lesson in humility.
He rode from the airport in a small gray Honda, dwarfed by a convoy of shiny SUVs and sleek Mercedes carrying Kenyan officials.
"His ride was the kind of car Kenya's affluent would not even accept in the exclusive membership clubs or the leafy gated communities," Kenya's Standard newspaper wrote on its website.
His visit will include a stop in Kangemi, a shantytown in Nairobi. In the Central African Republic, he will visit a refugee camp.
The Pope's message of hope, peace and reconciliation will reach out to a continent with the faith's fastest growing population.
"The Catholic population there (Africa) has grown by 238% since 1980 and is approaching 200 million," said Bill O'Keefe, a vice president at Catholic Relief Services
, a church-affiliated U.S. humanitarian group that does work in Africa.
"If the current trends continue, 24% of Africans will be Catholic by 2040."
Francis' predecessor, Pope Benedict, also visited several countries in Africa. During his nearly three decades in the papacy, Pope John Paul II also made dozens of trips to the continent.
Like most countries, the nations he's visiting have their own narratives of success and heartbreak.
Kenya and Uganda have been victims of the Islamist militant group Al-Shabaab, which has unleashed terror and mayhem in those countries, together with Somalia, where it's based.
His visit comes as dispirited Kenyans condemn their leaders over a series of corruption scandals, and Islamist militants' repeated attacks that have killed hundreds in recent years.
The Pope urged Kenyan leaders to be transparent and ensure equal wealth distribution to stop youth from radicalizing.
"Experience shows that violence, conflict and terrorism feed on fear, mistrust, and the despair born of poverty and frustration," he said.
He also called for the protection of traditional family values and children, whom he called a blessing.
Aside from visiting a region that will shape the face of the Catholic Church, the Pope's plan to stop at a mosque in the Central African Republic sends a powerful message.
In the Central African Republic, a Muslim rebel group overthrew the Christian president two years ago, prompting reprisal attacks by both Christian and Muslim militias.
Those attacks continue to this day, and have displaced hundreds of thousands of people.
"May my visit to Africa be a sign of the Church's esteem for all religions, and strengthen our bonds of friendship," Francis tweeted.