What will happen if the world becomes 4 degrees warmer?

Scientists predict we’re currently on track for a heating of somewhere between 3C and 4C for 2100 Four degrees may not sound like much – after all, it is less than a typical temperature change between night and day. It might even sound pleasant. However, if the entire globe heats by 4C it would render the planet unrecognisable from anything humans have ever experienced. So, what will happen if the world becomes 4 degrees warmer?