Most of the Observed Warming since the Mid-20th Century Likely Not from Human GHG Emissions?

World Climate Report
"The IPCC claims that it is “very likely” that “most” of the warming since then has been the result of human GHG emissions. In IPCC parlance, “very likely” means with a greater than 90% likelihood. The EPA parrots the IPCC’s claim in the Technical Support Document for their Endangerment Finding (TSD, p. 2): ......But one thing that we can say for sure is that the IPCC’s statement that “[m]ost of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG [greenhouse gas] concentrations” is badly in need of reassessment. The current literature shows that it cannot be justified.