FWiW I've been in geophysical exploration, mapping, and modeling since the 1980s and have no issue with the IPCC's reports on AGW. (I'm also responsible for posting this submission after reading the paper linked).
From your linked medium article:
By 2050 total human population will likely be under 2 billion.
Humans, along with most other animals, will go extinct before the end of this century.
These impacts are locked in and cannot be averted.
How can you validate (ie prove) these claims?
NB: Climate aside, the current "birthrate crisis" that the natalists scream about will see a flattening of population growth by 2050 .. that leaves ~ 8 billion to vanish to reach the 2 billion asserted.