That's not -20 OR +40. You're getting both. And while you're busy touting your preferences, I'm sure your farmers will be happy about their crops freezing, their land becoming unusable, your building being thoroughly unable to withstand such massive temperature swings and cracking, making it even worse to live in.
>We know for sure when we arrive at that point.
The moment you do arrive at the -20 every year point means that:
* You've spent the previous 40 years in denial that it happens more and more often
* You're on the path to -30 already, with no way to stop it.
Also -20 sounds better than +40. But that’s a preference lol