How to create net zero emission pathway chart?

Hello everyone,

I have the following two charts: 

I want to combine them into one chart to become something like this where the second chart is the gap between the two lines:

The link for the file:

https://1drv.ms/x/s!AttN7Ck7pK74iCkvcbOcGuszUNrd?e=Prjjgm