Frozen in the Bosphorus

At https://gsa.confex.com/gsa/inqua/finalprogram/abstract_55300.html (or http://chiefio.wordpress.com/2012/08/17/great-famine-of-1315-vs-the-sun/) … Herodotus recorded a frozen Bosphorus so it was not so unusual a happening. Since the modern era (AD) there have been several cold periods and the first was in the first century where 3 freezing events are recorded between 7 and 17AD according to Ovidius. There was another in the 4th century, reported by Scaliger (401AD) and several cold years in the 700s (the 750 to 800 window). In the 8th century the Bosphorus was repeatedly frozen and floating ice was present in the Sea of Marmara – in 739, 753, 755, 762, 928, 1015 and 1232, and again in 1620, 1669, 1755, 1823, 1849, 1862, 1893, 1929 and 1954, but none of this appears to correspond with general cold periods in northern Europe. For example, the 1929 event occurred in the middle of a warming period that was warmer than the late 20th century warming which appears to imply cold winters can occur on diverse occasions and ice in the Black Sea says a lot about weather in southern Russia/ Ukraine but little about global weather patterns. Or does it?