ABSTRACT
Pertinent, too, is whether the eleventh and twelfth centuries reveal any accentuation of the Rossby standing wave that flows north around the Himalayas and the Tibetan plateau to return south obliquely across the east Asian seaboard to trough out along a longitudinal axis lying just east of Japan. The comparative dryness that spread from the Yellow River valley to embrace the Yangtze during this time could have resulted from this. So could an initial coolness before warming resumed after 1200. Recent research has taken into account (a) the northward extent of herbs and citrus trees, and (b) medieval China’s reliance on an adjusted lunar calendar. The result has been to identify the thirteenth century as a time of peak warmth: averagely close to a degree kelvin higher in south Henan than has obtained of late.57 Also relevant to a geophysical interpretation is the ecological resilience Angkor Thom was able to display (see Chapter 5).
