In 2015 Coyne applauded Pope Francis for discussing the importance of caring for the environment and addressing the need for Christians to tackle the issue of climate change caused by human activity. He described Francis' encyclical "Laudato Si"' as "probably the most challenging encyclical since the great social encyclicals of Pope Leo XIII and Pope Pius XI in the 19th and early 20th centuries, which discussed the rights and duties of capital and labor". Coyne thought it "may very well provoke one of the most important dialogues between science and religion since the days of Charles Darwin".