Pope Francis is once again proving he has absolutely zero patience for climate change deniers.
Climate change is “one of the most worrying phenomena our humanity is experiencing,” the pontiff wrote Thursday in a letter sent to world leaders gathered for the United Nations’ annual climate change conference. He also warned participants against falling prey to certain “perverse” attitudes on the issue, including denial, indifference and resignation.
Such attitudes “certainly do not help honest research or sincere and productive dialogue on building the future of our planet,” Francis wrote, according to a translation provided by Vatican Radio. “We need an exchange that unites us all, because the environmental challenge we are experiencing, and its human roots, regards us all, and affects us all.”
The purpose of this year’s meeting, officially called the 23rd Conference of the Parties, is to hammer out how countries will implement the Paris climate accord. The landmark pact, which nearly 200 countries signed in 2015, aims to reduce greenhouse gas emissions around the world.
Francis didn’t berate any particular nation. But there’s only one country in the world that has remained opposed to the global agreement: the United States.
The Trump administration has also proposed rolling back the Clean Power Plan, an Obama-era federal regulation aimed at limiting greenhouse gas emissions from power plants. The president has instead promised to revive America’s coal industry and increase oil and gas production.
Francis, on the other hand, is a staunch advocate for action on the environment. In a 2015 encyclical called “Laudato Si,” he made it clear that he believes humans are partly to blame for the troubles the Earth is facing. He laid out a moral and theological case for addressing climate change and urged Catholics and others around the world to make the issue a top priority.
When Francis met Trump at the Vatican earlier this year, the pontiff sent the president off with some heavy reading ― a copy of “Laudato Si” was among the many gifts Francis gave Trump.
Judging by the administration’s decision to defend fossil fuels at the COP23 conference, there’s a chance Trump may not have gleaned much from his homework.
This article originally appeared on HuffPost.