He just schooled the world on why a warming planet deserves all our attention.
"The earth, our home, is beginning to look more and more like an immense pile of filth."
A tweet by an environmentalist? Nope. The pope!
The papal leader has always been a pretty devout champion for Mother Nature actually.
But this week, he upped his eco-friendliness to a whole other level.
A pretty-big-deal letter he wrote to other religious leaders leaked a few days ago. And, for the first time ever, the letter (often referred to as the "encyclical" for people who like big words) focused on taking action against climate change.
In the draft, which was by the Vatican on Thursday, June 18, 2015, the pope noted "the last decades of global warming have been mostly caused by the great concentration of greenhouse gases ... especially generated by human action."
Some might not realize that climate change is directly related to one of Pope Francis' concerns: inequality.
In April 2014, he tweeted: "Inequality is the root of social evil." Turns out, it's related to environmental evil too.
As the United Nations pointed out in a report last year, those who are "socially, economically, culturally, politically, institutionally or otherwise marginalized" will be most affected by drastic changes in the climate.
Climate change produces more extreme weather. And when horrible storms hit, poor communities are affected worse than rich ones.
Princeton University professor Michael Oppenheimer told The Guardian last year that rising global temperatures can also reduce crop yields, which can lead to higher prices for the food we eat. It's a change that'll disproportionately affect — yep, you guessed it — people living in poverty.
Of all the moral topics of interest to Catholics everywhere, Pope Francis decided to focus on climate change in this super-important letter.
That's pretty huge.