Increased Eurasian-tropical temperature amplitude difference in recent centuries: Implications for the Asian monsoon

A warmer Eurasian continent and stronger land/sea temperature gradient between Eurasia and the tropical oceans contribute to an intensified summer monsoon. We evaluate changes in the temperature difference between Eurasia and the tropics over 250 years using proxies of Eurasian surface air temperatures ( tree rings) and tropical sea surface temperatures (Indo-Pacific corals). These records show low-frequency correspondence with each other over this interval, and with other temperature and precipitation-sensitive proxies from the Asian monsoon regime. Greater warming is estimated for Eurasia ( amplitude = 1.70 +/- 0.28 degrees C; 1801 - 20 vs 1976 - 95) relative to the tropics (0.61 +/- 0.29 degrees C; 1806 - 25 vs 1937 - 56). The amplitude change from the 18th to 20th centuries is thus estimated to be about three times (1.5 - 6) greater over Eurasia than the tropics. This change may have contributed to an intensified Asian monsoon system over recent centuries, and to a decoupling of the monsoon and El Nino-Southern Oscillation in recent decades.