Mann is getting some serious competition for paleo-fraud.
The 1990 IPCC report showed the period 5,000 years ago to be about 1.5C warmer than the present, and it was almost 3C cooler 11,000 years ago

First IPCC report
But that wasn’t going to scare anyone, so the team came up with a new hockey stick, which disappears the end of the ice age.

Warming fastest since dawn of civilization, study shows – Science
The next graph overlays the new hockey stick on top of the 1990 IPCC version. Note that they have completely obliterated the entire paleo record. Impressive work.

It is trivial to demonstrate that this new hockey stick is complete, utter crap.
Sea level rose 40 metres from 10,000 to 8,000 years ago, indicating that a huge amount of ice melted – yet the new hockey stick shows no warming during that period. All that excess ice 10,000 years ago would have kept temperatures way down, as was shown in the 1990 IPCC graph. Half of Canada was still covered with ice 10,000 years ago, yet the new hockey stick shows that temperatures had already reached the Holocene Maximum. Impossible and absurd.
Most of the ice sheet was still present 11,000 years ago, yet the new hockey stick shows that temperatures were only 0.2C cooler than 1970. That would have been impossible with all that ice, which would have greatly suppressed temperatures – as was shown in the 1990 IPCC report.

File:Post-Glacial Sea Level.png – Global Warming Art
This overlay shows how the new hockey stick had already reached the Holocene Maximum, when almost half of the massive ice sheet was still in place.

Antarctic ice cores also show that temperatures were about 4C colder 11,000 years ago. The new hockey stick completely missed that, showing temperatures less than 1C cooler at that time.

New Antarctic Ice Core Data
Until the ice sheet melted 6,000 years ago, it would have been impossible to reach the Holocene Maximum – yet the new graph shows the peak temperatures occurring starting 10,000 years ago. Perhaps the authors think that ice wasn’t cold and white at that time?
How does this kind of garbage make it through peer review? They have violated the most basic laws of physics.