Read here. Map source here. Why do we say "huge" for the post-Roman period? Climate alarmistas are in an existential panic about a global temperature change of 0.7°C since 1880, per the National Climate Data Center (NCDC) data. A fair amount of that increase in temperatures since 1880 is natural versus the small AGW increase since 1970; and, the total 0.7 temperature change is significantly less than the post-Roman 2.0 degree change - 2.0 is huge versus 0.7.
The historical evidence points to past periods experiencing much greater temperature variation and associated climate change, and the South China Sea is yet another example.
"High-resolution Sr/Ca ratios of two Porites corals from the coast of Leizhou Peninsula in the northern South China Sea were measured.....From the Dark Ages Cold Period portion of the coral record, Wei et al. determined that the average annual SST was approximately 2.0°C colder than that of the last decade of the 20th century (1989-2000), while from the Roman Warm Period portion of the record they obtained a mean annual temperature that was identical to that of the 1989-2000 period as measured at the Haikou Meteorological Station.....As has been demonstrated many times before in a number of places throughout the world, these data indicate that the last decade of the 20th century did not display unusual or unprecedented warmth. Indeed, there were prior times within both the Medieval Warm Period and Roman Warm Period when temperatures were equally as warm as, or actually warmer than, what they have been recently; and all of these earlier warm periods occurred at times when the air's CO2 concentration was fully 100 ppm less than what it is today"
Additional climate history postings. Historical temperature charts. Modern temperature charts.