When most people read “Catholic Church” and “Science” in the same sentence, they are apt to think of the inquisition of Galileo, who narrowly escaped burning at the stake for espousing the Copernican view of a Sun-centered solar system. But that is old news. In 1992, Pope John Paul II stated his regret for Galileo’s treatment and in 2008, the 400th anniversary of Galileo’s first telescopic observations, Pope Benedict XVI praised his pioneering astronomy. The Vatican astronomer Brother Guy Consolmagno won the 2014 American Astronomical Society’s Carl Sagan Medal for Excellence in Public Communication in Planetary Science for his many books. 

The Catholic Church has also been forthright in its defense of evolution, Pope John Paul II telling the Pontifical Academy of Sciences in 1996 that “…new findings lead us toward the recognition of evolution as more than a hypothesis.” Catholic schools in the U.S. and elsewhere teach evolution both as a fact and as the result of the modern evolutionary synthesis, the updated version of Darwin’s theory. 

Though Young-Earth creationists maintain that our planet is only a few thousand years old, the Church has long accepted the antiquity of the Earth and the authenticity of the fossil record as validating the history of life. In 2004, before Cardinal Ratzinger had become Pope Benedict XVI, he endorsed a statement by the International Theological Commission that, 

The universe erupted 15 billion years ago in an explosion called the ‘Big Bang’ and has been expanding and cooling ever since. Later there gradually emerged the conditions necessary for the formation of atoms, still later the condensation of galaxies and stars, and about 10 billion years later the formation of planets. In our own solar system and on earth (formed about 4.5 billion years ago), the conditions have been favorable to the emergence of life.

Thus Pope Francis’s recent encyclical — Laudato Si, or “Praised Be”— is but the latest in a series of statements from the Catholic Church that offer increasingly strong support for science. Pope Francis’s eloquent encyclical not only does that, but it also casts the protection of the environment and the prevention of global warming as predominantly moral issues. He introduces the encyclical as an “Urgent appeal for a new dialogue about how we are shaping the future of our planet.” Francis asks for “a conversation which includes everyone, since the environmental challenge we are undergoing, and its human roots, concern and affect us all.” 

The question I am addressing is whether the Pope gets the science of global warming right. We should not be surprised if he does, for he was trained as a scientist: before becoming a priest, young Jorge Mario Bergoglio trained and worked as a chemical technician. Just as no one can discredit Francis’s moral standing, neither can anyone discredit his understanding of science.

As would any climate scientist today, Francis regards human responsibility for global warming as an indisputable fact. He does not present a list of arguments designed to persuade his readers that anthropogenic global warming is true, but simply says that it is true:

A very solid scientific consensus indicates that we are presently witnessing a disturbing warming of the climatic system. In recent decades this warming has been accompanied by a constant rise in the sea level and, it would appear, by an increase of extreme weather events, even if a scientifically determinable cause cannot be assigned to each particular phenomenon.

Exactly right. First, the consensus on anthropogenic global warming among publishing scientists exceeds 99.9%. Second, climate scientists do not claim that global warming “caused” a given heat wave, drought, or storm. Rather, they say that global warming has increased the odds of such events and is therefore partly responsible for the broad pattern of extreme weather. The Pope recognizes that global warming is not just something that will happen in the future: it is happening now and we need to respond now.

Further evincing his understanding, the Pope writes:

It is true that there are other factors (such as volcanic activity, variations in the earth’s orbit and axis, the solar cycle), yet a number of scientific studies indicate that most global warming in recent decades is due to the great concentration of greenhouse gases (carbon dioxide, methane, nitrogen oxides and others) released mainly as a result of human activity. Concentrated in the atmosphere, these gases do not allow the warmth of the sun’s rays reflected by the earth to be dispersed in space.

Again, exactly right. Several factors affect global temperature but only one can explain the rise in temperature since the 1970s: the increase in greenhouse gases from fossil fuel combustion. A climate scientist might argue that the last sentence of the quotation is an oversimplification in that it does not explain the mechanism by which greenhouse gases increase temperature. But the sentence as it stands is correct and sufficient for a general audience.

The Pope also demonstrates his understanding of the consequences of unchecked global warming: 

The melting in the polar ice caps and in high altitude plains can lead to the dangerous release of methane gas, while the decomposition of frozen organic material can further increase the emission of carbon dioxide. Things are made worse by the loss of tropical forests which would otherwise help to mitigate climate change. Carbon dioxide pollution increases the acidification of the oceans and compromises the marine food chain.

As result [of human activities] some species face extinction.

The effects of climate change will be felt for a long time to come, even if stringent measures are taken now.

As remarkable as Francis’s understanding of science is his powerful and eloquent language:

We are not God. The earth was here before us and it has been given to us.

The environment is… on loan to each generation, which must then hand it on to the next.

Leaving an inhabitable planet to future generations is, first and foremost, up to us. The issue is one which dramatically affects us, for it has to do with the ultimate meaning of our earthly sojourn. 

The Pope ends the encyclical with the moral argument in the form or a prayer, entreating God to,

Enlighten those who possess power and money that they may avoid the sin of indifference, that they may love the common good, advance the weak,
and care for this world in which we live.

The sentence that I will remember most is this one: “Doomsday predictions can no longer be met with irony or disdain.” Like climate scientists, the Pope regards global warming as threatening the future of humanity.