Climate change deniers in the United States are already spluttering with indignation. So far only one of the Republicans running for the US presidency views climate change as a possible danger, and now the pope has demanded action in the name of the poor, whom he says are bearing the brunt of the richer nations' greed. "The pope ought to stay with his job, and we'll stay with ours," says James Inhofe, chairman of the Senate environment committee. "I think we probably are better off leaving science to the scientists," adds Senator Rick Santorum.

In fact, the scientific claims in the papal encyclical are modest. They are merely the well-rehearsed arguments shared by the overwhelming majority of climate experts. What's new is the way Pope Francis shines a spotlight on the moral implications of their findings. The letter has been timed to have maximum public impact ahead of the pope's visit to the United States in September, when he will address Congress in Washington and the United Nations in New York. It could play a crucial role in pressuring political leaders to reach a substantive deal at the climate summit in Paris at the end of the year, and that appears to be his aim.

A moral issue

Climate change is a moral issue not only because we have a duty to save our planet for the sake of future generations but, more immediately, because the world's poor are much more impacted by climate change than the rich. Sea levels are rising. Stronger cyclones, more unpredictable rains, and larger and longer heat-waves are already lashing countries where people are struggling to get enough to eat.

The problem with the moral approach, however, is that there's a world of difference between acknowledging a responsibility and living up to it. A study conducted earlier this year by IPSOS Research found that a majority of Americans already view the reduction of carbon emissions as a "moral obligation." Seventy-two percent of those polled said that they even felt a moral responsibility to reduce emissions in their daily lives. However, that doesn't necessarily mean that they are ready to reduce their own air travel or give up their cars.

Bringing reverence into the debate

In his penetrating analysis of the climate change debate, "Don't even think about it," George Marshall has explained the reasons for our astonishing inaction. From the pessimism of the experts, which simply depresses us, to what the scientist and filmmaker Randy Olsen has called "the great unmentionable" (that the whole discussion about climate is, frankly, boring), it seems that hardly any of us are motivated to do anything about solving the problem. And that includes tree-huggers. You might separate your garbage and faithfully send your newspapers for recycling, but then in the warm afterglow of moral rectitude, you're just as likely to book a long-distance flight. Marshall, who worked for Greenpeace in the United States for many years, says environmentalists need to change their narrative. They need to connect to the "reverence" that millions of people feel for certain "sacred values." That is precisely what the pope's encyclical does.

The title and opening words, "Laudato si," are quoted from St Francis of Assisi's famous Canticle of the Sun, in which the "little poor man" from the Umbrian hills in the thirteenth century celebrated his kinship with the universe, calling upon "Brother Sun," "Sister Moon and the stars" and "Mother Earth" to lift up their hearts. It is no coincidence that Francis of Assisi is one of the best loved religious figures in history, even beyond the boundaries of Christianity. His kinship with the universe may appear sentimental to hard-nosed negotiators, but retold and explained by the popular pope from Argentina, it could influence millions of American voters. And that, in turn, could break the current deadlock in the climate change debate.

Do you think the Pope can put fresh impetus into the climate change debate? Share your thoughts in the comments section below.