How is that a reason to exclude it from the graph? Surely including it in the charts would strengthen the case for regarding it as a long term problem?

Excluding it subtly suggests that global warming is a short term phenomenon.

I agree with you that it's a long term problem. I won't stop until London is under a mile-high glacier!

There you go

https://xkcd.com/1732/

20,000 years enough?