That applies to both sides.
Potentially, but not as much as you seem to think
The problem is those responses are actually reasonably true. In a noisy data set like yearly temperatures, we expect there to be periods of slow temperature growth and periods of fast temperature growth due to short term variability so "that's not climate, that's weather" is true, 30 year averages are generally used to minimize year-to-year variability that can drown out the long term trend. We have had a confluence of natural factors working together to slow the surface air temperature growth over that period. Perhaps more importantly it's important to look at more than just the air temperature since the atmosphere only contains a small fraction of the heat content the earth can store.
That's a northern hemisphere temperature reconstruction, so it only covers half the world, and one of the authors of that paper, F. C. Ljungqvist, doesn't agree with your analysis:
Since AD 1990, though, average temperatures in the extra-tropical Northern Hemisphere exceed those of any other warm decades the last two millennia, even the peak of the Medieval Warm Period”
But then there are those on the same side who will mention a 20-100 year period because it suits their argument.
Potentially, but those are periods that are long enough to cancel out year-to-year variability, though, I can't actually remember seeing anyone use a period that was longer than 30 years. Maybe it's not that the period suits the argument but that when you look at periods longer than 20 years, the evidence strongly supports one side in this debate? If that's the case, then the people who look at and accept the evidence have little choice but to end up on the same side of this debate?
Oh how I wish people would stop quoting skepticalscience as if a blog is a scientific resource.
Skeptical science says exactly would you did, and most of what they say is sourced against another blog(RealClimate.org) which was at least started by a pair of actual scientists, but is still itself not subject to peer review either and really does not belong in your exhibit of evidences. This is is what is WRONG with the whole 'debate'. Way too many folks believe themselves to be protecting and promoting the science while waving their hands at blogs and re-hashing the summaries from them. :(
One of the scientists that started RealClimate is Michael Mann, here is his latest article on historic temperatures. Mann is (in)famous for the hockey stick graph. In his latest work here he's gone a long ways to trying to improve upon his original paper and although he only graphs the NA trend(citing that the SA data is of much lower quality), it very clearly shows temperatures as measured by proxy records matched or exceeded todays temperatures on multiple occasions in the last 2k years. He tries to down play this, but the data speaks for itself. Mann even notes himself that However, in the case of the early calibration/late validation CPS reconstruction with the full screened network (Fig. 2A), we observed evidence for a systematic bias in the underestimation of recent warming. Which is to say that proxy records appear to not track the recent temperature increase so well, and might well have done the same in the past. More over, actual statisticians that have looked at Mann's methods and techniques noted the same and many other concerns around confidence in historic reconstructions. Look for yourself here. there was considerable discussion, including on on RealClimate in which you'll likely find the assessment agreeable. Mann basically declare himself the victor in the exchange on his blog.
That's why I think the actual science must trump blogging by scientists. The final response to Mann's rebuttal of the statistician's work includes the following gems. It's worth a read if you like seeing the academic equivalent of a smack down. Probably why Mann reverts to his blog there after.
They note Mann et al
make no attempt to grapple with standard errors
make absolutely no attempt to deal with uncertainties, either for a given draw of data from the simulation or across repeated draws of the simulation
That all is to summarize that the scientific literature shows that there is absolutely NOT compelling, irrefutable evidence that current temperatures are radical compared to the last 2000 years. Moreover, even Mann's own work shows it likely to have been matched in the last 1k years.