The Pope said his long-awaited encyclical on the environment was almost finished and that he hoped it would be published in June, ahead of the UN climate meeting in Paris in November.
Speaking to reporters on the plane taking him from Sri Lanka to Manila, he was asked specifically if man was mostly to blame for climate change.
"I don't know if it is all (man's fault) but the majority is, for the most part, it is man who continuously slaps down nature," he said.
The words were his clearest to date on climate change, which has sparked worldwide debate and even divided conservative and liberal Catholics, particularly in the United States.
"We have, in a sense, lorded it over nature, over Sister Earth, over Mother Earth," said Francis, who since his election in 2013 has made many appeals for the protection of the environment.
"I think man has gone too far," he said. "Thank God that today there are voices that are speaking out about this."
Francis is expected to address the problems of the environment and climate change on Saturday (local time) when he visits Tacloban, the centre of the Philippines area devastated by last year's Typhoon Haiyan.
It killed about 6300 people and affected millions of others. About two million people are expected to attend an open-air mass on Saturday at Tacloban airport. The pope will also go into the devastated city centre to meet survivors.
Last month, about 190 nations agreed the building blocks of a global deal to combat climate change amid warnings that far tougher action will be needed to limit increases in global temperatures.
Under the deal reached in Lima, governments will submit national plans for reining in greenhouse gas emissions by an informal deadline of March 31, 2015 to form the basis of a global agreement due at a summit in Paris at the end of the year.
Francis faulted the Peru conference for not doing enough about climate change.
"The Peru meeting was nothing much, it disappointed me. I think there was a lack of courage. They stopped at a certain point. Let's hope the delegates in Paris will be more courageous and move forward with this," he said.
