The pontiff is raising the issue on his tour of the USA and spoke about the need to act in an address at the White House.
Responding to what's he's had to say, Mrs Clinton, writing for the National Catholic Reporter said: "As a person of faith, a mother, and a grandmother, I am deeply moved by Pope Francis' recent teachings on climate change - to reflect and above all to act.
"The effects of climate change are too obvious to ignore. We can see them with our own eyes, in our own communities. In California, higher temperatures have worsened a brutal drought, which has lasted four years and shows no signs of abating. In New York, flooding from Hurricane Sandy was made worse by the fact that New York Harbor is nearly a foot higher now than it was 100 years ago. In Alaska, villages that were settled before the United States even existed are facing imminent destruction because of a rising ocean, retreating ice and more violent storms.
"There's no time to waste. We have to act now."
Pope Francis spoke at the UN yesterday before leading mass in front of 20,000 people at Madison Square Garden.
Today he's in Philadelphia for the World Meeting of Families.