Read here. The Indo-Pacific ocean area represents the warmest volume of water known to exist naturally. Soooo, is that pool of warm water the warmest it's ever been? Is it experiencing the "unprecedented" warmth that alarmists always speak of? Nope, not even close - it's "lukewarm" compared to the Roman and Medieval warming eras. (click on image to enlarge)
Oppo et al. derived a continuous sea surface temperature (SST) reconstruction from the Indo-Pacific Warm Pool (IPWP), which they describe as "the largest reservoir of warm surface water on the earth and the main source of heat for the global atmosphere."....spans the past two millennia and, as they describe it, "overlaps the instrumental record, enabling both a direct comparison of proxy data to the instrumental record and an evaluation of past changes in the context of twentieth century trends." Reconstructed SSTs were, in their words, "warmest from AD 1000 to AD 1250 and during short periods of first millennium." From the authors' Figure 2b, adapted below, we calculate that the Medieval Warm Period was about 0.4°C warmer than the Current Warm Period.
More historical charts here. Other climate history postings here. Modern temperature charts.