TUHO: Zdrojová data jsou z 1984:
Sci-Hub | North Atlantic climatic oscillations revealed by deep Greenland ice cores. Geophysical Monograph Series, 288–298 | 10.1029/GM029p0288
https://scihub.bban.top/https://agupubs.onlinelibrary.wiley.com/doi/10.1029/GM029p0288
Sceptical science:
First, if you want to be taken seriously in a scientific discussion, don't source evidence from astrology sites, as you have done with that first chart. Granted the author of that site attributes the chart to a climate scientist (Schoenwiese) without specification as to year, or publication. Fortunately the chart has been examined as an example of the misuse of scientific charts by climate "skeptics" (Schneider et al 2014). The chart is from Schoenwiese 1995, and based on Daansgard (1984) (published online in 2013). Schneider et al (2014) comment:
"many authors of skeptical media (for example Avery, 2009, and Vahrenholt und Lüning, 2012) fail to mention that this temperature estimate is based on an ice-core record from Greenland and may thus not be representative of global temperatures."
Of course, in your version it is labelled Northern Hemisphere temperatures, not global temperatures. The point still stands, however. A Greenland ice core no more shows Northern Hemisphere temperatures by itself than does a thermometer in Moscow show temperatures in Tucson, Arizona. It can be used (as Daansgard used it) as an indication of North Atlantic temperatures, but beyond the North Atlantic, its accuracy as a temperature index will rapidly fall.
Schneider et al go on:
"Most importantly, in Schönwiese's 1995 version the current and near future temperature changes are included. The recent warming goes far beyond the historic warm periods of the last 12000 years and should therefore have been included in the graph."
(My emphasis)
Skeptical Science Search Results
https://skepticalscience.com/search.php?t=c&Search=Medieval+Warm+Period