Catholics should care about climate Change because if the Ocean rise just 15 meters, the Vatican will be in jeopardy of flooding.

Just is doing a lot of lifting in that sentence.

For those using freedom units there is roughly 3 feet per meter, making it 45 feet.

15 meters is about the height of a 4 story building. A shit tonne more problems will occur if the world lost 4 stories worth of land.

Also consider that between 1901 and 2018 the ocean rose by 15 to 25 millimetres (6-10 inches) or 0.015 meters it will be far beyond our grandchildrens lifetime that the increase hits 1 meter.