Simply because the IPCC is, and has been, tainted beyond the pale.
Don Surber has the meat of the matter exposing the IPCC for what it is, straight from a tell all book “The Delinquent Teenager Who Was Mistaken for the World’s Top Climate Expert,” an expose of the 2007 IPCC report.
Finally. The dogs are loose. Read it. You won’t be surprised, but it will be a confirmation.