While Catholic Republican leaders try to stay in line with the teachings of the Catholic Church on subjects such as abortion, euthanasia, embryonic stem cell research and same-sex marriage, they differ on the death penalty and contraception. Pope Francis' 2015 encyclical "Laudato si sparked a discussion on the positions of Catholic Republicans in relation to the positions of the Church. The Pope's encyclical on behalf of the Catholic Church officially acknowledges a man-made climate change caused by burning fossil fuels. The Pope says the warming of the planet is rooted in a throwaway culture and the developed world's indifference to the destruction of the planet in pursuit of short-term economic gains. According to "The New York Times", "Laudato si put pressure on the Catholic candidates in the 2016 election: Jeb Bush, Bobby Jindal, Marco Rubio and Rick Santorum. With leading Democrats praising the encyclical, James Bretzke, a professor of moral theology at Boston College, has said that both sides were being disingenuous: "I think it shows that both the Republicans and the Democrats... like to use religious authority and, in this case, the Pope to support positions they have arrived at independently... There is a certain insincerity, hypocrisy I think, on both sides". While a Pew Research poll indicates Catholics are more likely to believe the Earth is warming than non-Catholics, 51% of Catholic Republicans believe in global warming (less than the general population) and only 24% of Catholic Republicans believe global warming is caused by human activity.