Newton et al. analyzed sediment cores from the Makassar Strait between the Indian and Pacific Oceans and confirmed that the hottest sea-surface temperatures took place some 800+ years ago, during the Medieval Period. These scientists noted that Medieval Warming took place during a solar activity maximum.
"Based on Mg/Ca ratios of the planktonic foraminifer Globigerinoides ruber that they obtained from a sediment core that was extracted from the seabed at the southern end (~5.3°S, 117.8°E) of the Makassar Strait...as they describe it, that "the warmest sea surface temperatures of the past 2000 years occurred between 1000 and 800 years ago," which period, they say, "is broadly coincident with the Medieval Warm Period as reflected in Northern Hemisphere temperature anomaly reconstructions."
"...used to reconstruct surface-water temperature (SST), sea-surface salinity (SSS), and seawater density variability over the past 2000 yr. Maximum SST and SSS occurred at both sites between 850 and 700 yr ago, coinciding with the Medieval Solar Maximum and Medieval Warm Period (ca. 1000–700 yr ago). SST and SSS declined at both locations after 700 yr ago and reached minimum values during the Little Ice Age, between 300 and 100 yr ago." [Alicia Newton, Robert Thunell and Lowell Stott 2011: Geology]