Pope Francis calls global warning a "sin"

He said the faithful should ask forgiveness for the ‘sins’ against the environment that have been committed by the ‘irresponsible, selfish’ and profit-motivated economic and political system.

He called for all of humanity to take concrete steps to change course, starting with repaying what he called the ‘ecological debt’ that wealthy countries owe the poor.

‘Repaying (the debt) would require treating the environments of poorer nations with care and providing the financial resources and technical assistance needed to help them deal with climate change and promote sustainable development,’ he wrote.

On a smaller, individual scale, recycling, turning off the lights and carpooling can also help, he said.