He has 12.9 million Twitter followers. Millions of people flock to see him every year. And he has the ear of world leaders. So when the Pope speaks up about climate change, he has more clout than most.

Ahead of a worldwide day of prayer for the Earth, the Pope this week urged politicians to “listen to the cry of the Earth and the cry of the poor, who suffer most because of the unbalanced ecology”.

Climate prayers and climate deniers

Pope Francis is outspoken on matters of global concern, including climate change. Meeting President Trump ahead of the US’s momentous decision to leave the Paris climate accord earlier this year, Pope Francis gave him a copy of Laudato Si, his 2015 encyclical - the highest form of papal writing - on climate change.

Laudato Si triggered the establishment of Global Catholic Climate Movement in 2015. It brings together Catholics worldwide to raise the issue of climate change on the global agenda.

In 2015, he designated September 1st as the church’s day for prayer for the environment.

Image: REUTERS/Max Rossi

Here are five of the Pope’s memorable quotes about the importance of looking after the planet.

1. Ahead of his encyclical in 2015 he tweeted “The Earth, our home, is beginning to look like an immense pile of filth”

2. At the conclusion of a Vatican summit on the environment in 2015: “Human-induced climate change is a scientific reality, and its decisive mitigation is a moral and religious imperative for humanity. In this core moral space, the world’s religions play a very vital role.”

3. Writing to the Australian prime minister Tony Abbott ahead of the country hosting the G20 in 2015: "There are constant assaults on the natural environment, the result of unbridled consumerism, and this will have serious consequences for the world economy."

4. Speaking on 1st September last year: “We must not be indifferent or resigned to the loss of biodiversity and the destruction of ecosystems, often caused by our irresponsible and selfish behaviour. Because of us, thousands of species will no longer give glory to God by their very existence. We have no such right.”

5. Tweeting in June this year shortly after the US withdrew from the Paris climate accord: “We must never forget that the natural environment is a collective good, the patrimony of all humanity and the responsibility of everyone.”