Reference
Newton, A., Thunell, R. and Stott, L. 2006. Climate and hydrographic variability in the Indo-Pacific Warm Pool during the last millennium. Geophysical Research Letters 33: 10.1029/2006GL027234.
What was done
Working with a sediment core collected at 5°12.07'S, 117°29.20'E in the Indo-Pacific Warm Pool (one of the warmest regions in the modern oceans), Newton et al. analyzed planktonic foraminiferal (Globigerinoides ruber) Mg/Ca and δ18O data to derive high-resolution summer sea surface temperature (SST) and salinity histories extending back in time about a thousand years.
What was learned
The researchers' work revealed, in their words, that "the warmest temperatures and highest salinities occurred during the Medieval Warm Period," which lasted from about AD 1020 to1260. Over this period, summer SSTs averaged about 29.7°C, as best we can determine from their graph of the data, with a peak of about 30.9°C in the vicinity of AD 1080, which values are to be compared with the region's average modern summer SST of 29.0°C, which is significantly lower than that of the Medieval Warm Period. Likewise, they found that "the coolest temperatures and lowest salinities occurred during the Little Ice Age," the lowest temperatures of which occurred "around AD 1700, during the period of reduced solar intensity known as the Maunder Minimum," when summer SSTs "were 1.0-1.5°C cooler than present," presumably due to the lower solar activity of that period.
What it means
In contradiction of the climate-alarmist claim that the Medieval Warm Period and Little Ice Age were merely regional phenomena confined to countries surrounding the North Atlantic Ocean, Newton et al. say their data from the Makassar Strait of Indonesia clearly indicate that "climate changes during the Medieval Warm Period and Little Ice Age were not confined to the high latitudes," nor, we would add, to countries bordering the North Atlantic Ocean.