Pope Francis has more epistemological and moral authority than any scientist, philosopher, lawyer, or politician. He has the second most popular twitter feed, and his messages are more likely to be retweeted than anyone else’s. The Pope has the power to order some and to persuade others. Most of all he has the power to affect the global agenda. When the Pope speaks, people listen.

Pope Francis commands respect for many reasons. He sits atop a hierarchy with which 1.2 billion people are affiliated. Organized more like a multinational corporation than a nation-state, the Catholic Church and its members are spread across all the countries of the world. But it is not just Catholics who take his pronouncements seriously. As a man of the South, occupying an office in the North, with no national allegiance except to a country of 110 acres with a population of 842, he is uniquely situated to speak out on global issues. Laudato Si’ also commands respect because it is an astonishingly well-written argument for a powerful point of view, one that in various bits and pieces can be found in the small journals and ignored books of environmental philosophy and theology.

The brokerage firm, E.F. Hutton, used to have a tagline that went, “When E.F. Hutton speaks, people listen.” On climate change, the Pope has spoken, but will people listen? And should they? The first question is empirical; the second, normative.

The papal encyclical, Laudato Si’, was released in May 2015 to much acclaim. It is an extraordinarily wideranging document. Although I will focus, in particular, on its discussion of climate change, it is worth noting that the encyclical addresses virtually the entire litany of environmental problems—loss of biodiversity, hazardous chemicals and wastes, marine pollution, replacement of virgin forests with monoculture plantations, and lack of access to clean drinking water, among others—as well as related social problems such as extreme poverty and urban overcrowding.

The Encyclical Letter of Pope Francis centers on an interpretation of Biblical texts that establishes human power over other creatures and the right to beneficial use of them, imposing a type of guardianship or a trust, not a right of ownership. The Pope emphasizes that message he presents is intended to be a universal one, not limited to all Catholics or even all Christians, but to “every person living on this planet.” The encyclical begins by reviewing several aspects of the present ecological crisis, then considers some principles drawn from the Judaeo-Christian tradition which can render commitment to the environment more coherent.

The recent Encyclical by Pope Francis, Laudato Si’, On Care for our Common Home, is a remarkable document, both original and continuous within the tradition of Catholic social doctrine. Emerging from and grounded in a very specific religious tradition and constrained by the peculiar encyclical literary form, the document nonetheless seeks to open a dialogue with “every person living on this planet,” about care for our common home. Using the urgency of addressing global climate change as its point of departure, the Encyclical does a superb job summarizing the scope of the present environmental crisis and the disproportionate harms suffered by vulnerable populations of the poor and excluded. It also provides a careful analysis of the root causes of environmental degradation, mapping out the complex linkages and tensions between globalization, economic growth, liberalized trade, unsustainable patterns of consumption and production, environmental degradation, involuntary migration, immiseration and growing inequality. In this respect, the Encyclical, may well come to serve as a useful position paper for the upcoming Paris climate change negotiations or as a background text for a course on climate change or sustainable development. Yet, properly understood, this is not its true purpose. Rather, in its deepest sense, the Encyclical is an appeal to all of humanity to listen to “the cry of the earth and the cry of the poor,” to reject the “throwaway” culture of consumerism, and to embrace a culture of care and a commitment to pursue integral ecology. It is, in other words, a call to ecological conversion: a call addressed not only to individuals but also to individuals-in-community.

A fundamental theme running through the remarkable 192-page Papal Encyclical on Climate Change is the notion of solidarity—;between nations and peoples, and between and within generations. In the words of the Encyclical, “[w]e require a new and universal solidarity.”. This translates, in the Encyclical’s vision, into principled cooperation between states and peoples, because “[a]ll of us can cooperate as instruments of God for the care of creation, each according to his or her own culture, experience, involvements and talents.”. In the international climate change regime this vision takes the form of the principle of common but differentiated responsibilities and respective capabilities (CBDRRC), a principle that the Encyclical explicitly endorses. The CBDRRC principle, however, lends itself to varying interpretations and has thus proven deeply contentious as the basis for climate cooperation. This is in particular in relation to the 2015 climate agreement that is due to be finalized in Paris in December 2015. This short essay explores the extent to which the Encyclical supports one or the other interpretation of this principle, and how closely aligned (or not) the Encyclical’s vision is to the emerging 2015 climate change agreement.

As the world turns its attention to Paris this December, all eyes will be on international decisionmakers, including those from the United States, to see if meaningful progress on climate change can finally be made. Climate change, of course, is the great environmental challenge of our time, a challenge that is irrevocably bound up with energy production and consumption. This “super wicked” problem long has been seen as a political, economic, ecological, and social one. However, as Pope Francis’ encyclical makes clear, it is a moral problem as well.