Problem is squidgy, you are effectively asking for a review of the whole basis of climate science. That's no small task.
I'll throw you two bones to consider, rebutting two key aspects of what appears to be your hypothesis:
1. Models aren't good enough.
Have a look at this:
back in 2013/14 it was considered that models did not appear to replicate the holocene well,
although proxy data issues were also considered a possible cause of the apparent discrepancy between models and proxy temp data
http://www.pnas.org/content/111/34/E3501
then this study in may last year - which provided further holocene proxy data that now indicates that the models have in fact been correct, and it was a major gap in the proxy data and known causes of seasonal differences that caused the observed discrepancy
https://www.theguardian.com/environ...drum-across-the-history-of-human-civilization
As the guardian article summarised
"There are several important points we can take from the Baker study. First,
climate models are able to simulate climate changes over the history of human civilization fairly accurately. [i.e. >10,000 years!] Second, when there’s a discrepancy between data and models, people have a tendency to distrust the models, but sometimes the problem lies more in the data. Third, if not for the human influence, the climate would continue the stable conditions of the past 7,000 years, during which time human civilization developed and thrived."
If models can
a) replicate the change in holocene temperatures, i.e. over the entire history of human civilisation, well enough to point to possible issues with proxy data that have subsequently been confirmed ...
and
b) as has been discussed here several (million) times, models can hindcast the last century well and have been shown to forecast the more recent decades well ...
... then why would you claim the models are not good enough.
Now, we don't want to get carried away and imply this is an exact thing, and the science acknowledges uncertainty in climate sensitivity. But all indications are that anywhere in the range of sensitivity indicated by the science requires us to dramatically reduce greenhouse gasses. Lower sensitivity only gives us more time to achieve that to hold warming to 2 or 1.5 degrees, and regardless that will be a challenging task.
2. Roman and Medieval "warm" periods.
You suggest that our current warming may simply be consistent with those two historic periods.
Firstly the stuff above on modelling strongly suggests otherwise. Models excluding anthropomorphic greenhouse gasses do not replicate temperature patterns of the last 100 years, while models including those greenhouse gasses do. So we have scientific analysis that strongly demonstrates that the current warming is not natural and is due to greenhouse gasses.
Secondly, the evidence of those "warm" periods remains less than luke warm about them being warm.
Box 6.4 here gives the IPCC assessment of the medieval period.
https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-6.html
that concludes "the evidence is not sufficient to support a conclusion that hemispheric mean temperatures were as warm, or the extent of warm regions as expansive, as those in the 20th century as a whole, during any period in medieval times (Jones et al., 2001; Bradley et al., 2003a,b; Osborn and Briffa, 2006)."
further in that same link
"On the evidence of the previous and four new reconstructions that reach back more than 1 kyr, it is likely that the 20th century was the warmest in at least the past 1.3 kyr."
