1.5 degrees is when the tipping points start to tip.
Fun fact: the planet has been at +1.5℃ for the last 14 months.
The reason why we aren’t officially at +1.5℃ is because the official designation is a political one, which requires some insanely long time at +1.5℃ - usually on the order of 8-20 years, depending on the org - before it can be said that we have “breached +1.5℃”.
Politicians are morons in the pockets of the Parasite Class.