The new papal encyclical on the environment is a ringing call to action, a critique of consumerism and a prophetic warning about the dangers of ignoring what Pope Francis calls “the ecological crisis.”
But amid all his soaring rhetoric, did the pope get the science right?
The short answer from climate and environmental scientists is that he did, at least to the degree possible in a religious document meant for a broad audience. If anything, they say, he may have bent over backward to offer a cautious interpretation of the scientific facts.
For example, a substantial body of published science says that human emissions have caused all the global warming that has occurred over the past century. Yet in his letter, Francis does not go quite that far, citing volcanoes, the sun and other factors that can influence the climate before he concludes that “most global warming in recent decades is due to the great concentration of greenhouse gases” released mainly by human activity.
Michael E. Mann, a climate scientist at Pennsylvania State University, pointed out that the bulk of the evidence suggests that solar changes and volcanoes have slightly counteracted the warming effect of greenhouse gases.
“Human activity is most likely responsible not just for ‘most global warming’ but all of it, and then some, because natural factors have been acting slightly in the other direction,” Dr. Mann said.
When reciting facts, as opposed to making judgments, the pope aligns himself squarely with mainstream scientific thinking. Indeed, those sections of the document could serve as a syllabus for Environmental Science 101 in just about any college classroom these days.
The pope offers elementary descriptions of a litany of ecological problems, global warming chief among them, that include air and water pollution, the wanton destruction of forests, the wasteful use of resources and many more.
When the pope does transition in his encyclical from fact to judgment, though, his language is less measured.
“The earth, our home, is beginning to look more and more like an immense pile of filth,” Francis declared. “In many parts of the planet, the elderly lament that once beautiful landscapes are now covered with rubbish.”
The pope is careful to acknowledge that there has been some progress, with stricter environmental laws in some countries leading to cleaner air and water.
But he points out, and environmental experts agree, that impoverished people bear a disproportionate burden from pollution in rich and poor countries alike. They have benefited least from fossil fuels, he adds, but are first in line to suffer as the effects of global warming intensify.
The Vatican has been consulting for many months with leading experts. Among them was Hans Joachim Schellnhuber, who is founder and head of the Potsdam Institute for Climate Impact Research and a primary environmental adviser to Chancellor Angela Merkel of Germany.
In an interview, Dr. Schellnhuber, who was raised a Lutheran in a small German town, said he was especially impressed with the pope’s determination to reach beyond the Catholic faithful, attempting to speak, in Francis’ own words, to “every person living on this planet.”
The hard lesson scientists have learned in recent years, Dr. Schellnhuber said, is that presenting the facts and data about global warming and other environmental problems has not been enough to move the public to action. The issues have become so serious that only a broad moral awakening can offer hope of solving them, he said.
“We have pushed the planet into a major environmental crisis, so creation is at stake,” Dr. Schellnhuber said.
In aligning himself with mainstream scientific thinking, Francis invites criticism from people who dispute the science of climate change — indeed, these contrarians were vociferously attacking his document even before it was issued.
But the more meaningful critiques in coming weeks may come from those experts schooled in environmental policy. The scattered policy prescriptions in the document do not display the meticulous framing of the scientific statements.
For instance, Francis devoted a long paragraph to criticizing an approach called carbon trading that can be used to put a price on greenhouse emissions, even though many environmental economists favor that approach. Despite problems in some jurisdictions, it has been shown to work well in others, including California.