When Pope Francis died, the world lost not only the leader of the Catholic Church but also the first pontiff in history to take a public stance on combating climate change.
Tributes began pouring in Monday morning after the Vatican announced the death of Pope Francis, including from leaders in the fight against climate change who praised the late pontiff for supporting those efforts.
United Nations Secretary General António Guterres said the U.N. was "greatly inspired" by Francis' "commitment to the goals and ideals of our organization."
"Pope Francis was a transcendent voice for peace, human dignity and social justice," Guterres said in a statement. "He leaves behind a legacy of faith, service and compassion for all – especially those left on the margins of life or trapped by the horrors of conflict."
Guterres also credited Pope Francis for helping to rally nearly 200 countries to sign the 2015 Paris Agreement, the international treaty meant to rally the global effort to address climate change and limit global warming. In September 2015, during Francis' visit to U.N. headquarters in New York City, he delivered an address to world leaders gathered there that urged them to adopt the 2030 Agenda for Sustainable Development, described by the U.N. as "the world’s roadmap for ending poverty, protecting the planet and tackling inequalities."
Francis' efforts to call attention to the need to protect the environment were apparent from the start of his papacy. Just days after being elected in March 2013, Francis made clear his views on the need to conserve the environment during his inaugural mass in Saint Peter's Square, urging all people living on Earth – especially global leaders in economic, political and social life – to assume the role of "protector."
"It means protecting all creation, the beauty of the created world, as the Book of Genesis tells us and as Saint Francis of Assisi showed us," Francis said during the inaugural mass. "It means respecting each of God’s creatures and respecting the environment in which we live."
Francis also penned the first-ever encyclical letter on climate change in May 2015, in which he further invoked the past writings of St. Francis of Assisi, from whom Francis took his papal name, and who described the world as "like a sister with whom we share our life."
"This sister now cries out to us because of the harm we have inflicted on her by our irresponsible use and abuse of the goods with which God has endowed her. We have come to see ourselves as her lords and masters, entitled to plunder her at will," Francis wrote, in part.
During a visit to the Philippines in January 2015 following Super Typhoon Haiyan's devastating November 2013 strike, Francis was asked by a journalist whether climate change is mostly the result of human causes, to which the pope responded, "I don’t know about entirely, but mainly, for the most part, it is human beings who abuse nature, constantly."
"An old farmer once told me, 'God always forgives, we men and women sometimes forgive, but nature never forgives,'" Francis said.
Francis also took aim at oil executives during a Vatican conference in 2018. While the pope acknowledged some reduction efforts, he described the continued search for fossil fuel reserves as "worrying."
His call to address climate change grew more urgent in 2023, when Francis issued a lengthy apostolic exhortation titled "To All People of Good Will on the Climate Crisis," saying not enough had been done to address the issue in the years since he first spoke of it.
"With the passage of time, I have realized that our responses have not been adequate, while the world in which we live is collapsing and may be nearing the breaking point," Francis wrote, in part, adding that "it is indubitable that the impact of climate change will increasingly prejudice the lives and families of many persons. We will feel its effects in the areas of healthcare, sources of employment, access to resources, housing, forced migrations, etc."
"This is a global social issue and one intimately related to the dignity of human life," Francis declared.
Francis was slated to become the first pope to attend the U.N. Climate Change Conference in November 2023, but he had to cancel his appearance due to illness.
Many world leaders hailed Pope Francis in the hours after his death for his dedication to the protection of the environment.
Former U.S. President Joe Biden lauded Francis's efforts to "protect our planet from a climate crisis" in a statement posted to X.
Former President Bill Clinton and Secretary of State Hillary Clinton also acknowledged Francis' work on climate change in their statement on his passing.
"Hillary and I mourn the passing of His Holiness Pope Francis and celebrate his remarkable life and legacy: promoting peace, economic inclusion, and social justice; and fighting climate change, particularly its threat to the lives and livelihoods of the world’s poorest citizens," Bill Clinton wrote.
Former U.S. Vice President Kamala Harris described Pope Francis as a "visionary leader who dedicated his life to service and justice," writing on X that he "encouraged us to protect our planet, championed a more inclusive church, and cared for all of God’s children – especially the most vulnerable among us."
South African President Cyril Ramaphosa said in a statement that the pope advanced a world view of "responsible and sustainable custody of the natural environment."
Cardinal Kevin Farrell, the Irish-born 77-year-old president of the Vatican City State Supreme Court, will serve as head of the Catholic Church until a new pope is elected, according to the Vatican.
ABC News' Matthew Glasser and Dan Peck contributed to this report.
