Environmental negotiators meeting in Paris should strike a climate change deal to save a world "at the limits of suicide," Pope Francis said on Monday.

"I am not sure, but I can say to you 'now or never'," he told a group of reporters aboard the papal plane, en route home from Africa, according to Reuters. "Every year the problems are getting worse. We are at the limits. If I may use a strong word I would say that we are at the limits of suicide."

The comments come at the start of a United Nations-sponsored environmental summit in Paris, which nearly 150 world leaders are expected to attend.

Politicians have generally "done little" to deal with the growing problem, Francis said, according to the National Catholic Reporter.

"I am sure they have the good will to do it. And I wish that it will be so, and I pray for this," he said.

The urgent call is nothing new for Francis. In June, he laid out the case, in a 192-page paper, for a collaboration between science and religion to combat climate change.

“The Earth, our home, is beginning to look more and more like an immense pile of filth,” Francis wrote at the time.

On Monday, he cited glacial melt in Greenland and rising sea levels in low-lying countries as specific causes of concern.

Other world leaders have sounded the siren on the issue, too. Speaking at the summit, President Obama on Monday quoted Martin Luther King Jr. in warning that “there is such a thing as being too late.”

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