I'm not going to wade into the science here because it's beyond my knowledge.
However, a quick scan of the report shows that Breitbart misinterpreted the headline.
For example, the report acknowledges that adjusting GAST is necessary:
"The adjustment of raw surface temperature data is clearly necessary to overcome numerous challenges."
"All of these challenges notwithstanding, calculation of GAST requires
that, after the raw data are collected, some adjustments clearly must
be made"
The report concludes that these adjustments systematically made warming appear worse.
Even if we accept all these analyses at face value, this is a far cry from "recent global warming is fabricated." Rather, it's a claim that statistical adjustments made get the answer wrong, and tend to do so in one direction.
That doesn't mean fabrication, which implies dishonestly on the behalf of the climate science researchers. Anyone who has worked with data knows you often have to make these types of decisions, and you typically do so by following other practices in the field. It's very possible that standard practice is wrong and a lot of people get the wrong answers. This can happen, and frequently does, without any "fabrication" or even poor reasoning. Science corrects itself and tries to get better answers over time.
In any event, I'd wait for a rebuttal before you go and conclude that recent conclusions about "hottest ever" are wrong.