A new study has found that by the end of the century swaths of the Middle East may become so hot and humid, they will be “intolerable to humans.” Due to human-driven climate change from the burning of fossil fuels — much of it coming from oil-rich countries in the Middle East — cities across the Persian Gulf could reach a point where people cannot safely be outside for more than a few hours. The study in the journal Nature Climate Change comes as Catholic leaders from five continents have issued an appeal to negotiators at the upcoming Paris climate summit to adopt a “transformative” agreement to address climate change.