Literature like this makes me happy, because it is further evidence that the alarmists have very little material left. Mercifully we may have hit the high-water mark of this generation of misanthropic environmentalist nonsense and can now enjoy several decades of joking about it. The "Recursive Fury" paper[0] was probably the actual high-water mark, and this looks like pretty much the same tactic.
The fact remains that current proxy studies are thoroughly insufficient as p̶r̶o̶o̶f̶ evidence of any long-term trend we can expect to continue in a non-linear system as complex as the global climate.
I guess these folks think I must be unhappy about the "necessary solution" (oh hey, it turns out to be reorganizing society according to their political beliefs!) but that amounts to an elaborate and silly ad hominem, nothing more. I think I'll write more about the "psychology journal ad-hominem" because it has become annoyingly common in recent years.
The science of climate is not settled, and will not be settled in your lifetime. Get used to it.
[0]http://journal.frontiersin.org/article/10.3389/fpsyg.2013.00...