Pope Francis has criticised those who deny the science behind global warming and urged negotiators at climate talks in Germany to avoid falling prey to such "perverse attitudes".
Francis issued a message to the Bonn meeting, which is working to implement the 2015 Paris accord aimed at capping global emissions.
He called climate change "one of the most worrisome phenomena that humanity is facing" and urged negotiators to take action free of special interests and political or economic pressures.
Francis did not cite any countries by name but the US has announced it is withdrawing from the Paris accord.
President Donald Trump has nominated several people in his administration who question scientists' conclusions that human activity is behind the global rise in temperatures.
At the same time, the US administration has promoted the use of fossil fuels like coal for energy needs.
In his landmark 2015 environmental encyclical, Francis said global warming is "mainly" due to human activity and he called for fossil fuels to be progressively phased out without delay.
In his message, the Argentine pope claimed efforts to combat climate change are often frustrated by those who deny the science behind it or are indifferent to it, those who are resigned to it or think it can be solved by technical solutions, which he termed "inadequate".
"We must avoid falling into these four perverse attitudes, which certainly don't help honest research and sincere, productive dialogue," he said.