The Ming Dynasty Mega-drought (MDMD) (1637-1643) occurred at the end of Ming Dynasty and is the severest drought event in China in the last millennium. This unprecedented drought contributed significantly to the collapse of the Ming Dynasty in 1644, casting profound impacts on Chinese history. Here, the physical mechanism for the MDMD is studied. Based on paleoclimate reconstructions, we hypothesize that this drought was initially triggered by a natural drought event starting in 1637, and was then intensified and extended by the tropical volcanic eruption at Mount Parker in 1641. This hypothesis is supported by the case study of the Community Earth System Model-Last Millennium Experiment archive as well as sensitivity experiments with volcanic forcing superimposed on natural drought events. The volcano-intensified drought was associated with a decreased land-ocean thermal contrast, a negative soil moisture response and a weakening and eastward retreating West Pacific Subtropical High. Plain Language Summary The collapse of Ming Dynasty at 1644, and in turn, the historical transition from Ming Dynasty to Qing Dynasty significantly changed the Chinese history into a long period of conservative policy. The collapse of Ming Dynasty at 1644 is contributed greatly by the Ming Dynasty Mega-drought (MDMD) (1637-1643). In this study, based on paleoclimate reconstructions and climate modelling, we show that the MDMD is triggered by a natural drought event, and is then intensified and extended by the strong volcanic eruption at Mt. Parker in 1641. This “superposition” mechanism of MDMD and the spatiotemporal characteristics of this drought is reproduced by our volcanic sensitivity experiments with volcanic forcing superimposed on natural drought events, and the results demonstrate that the explosion of Mt. Parker at the end of a natural drought event amplified and extended the drought for 3 years, generating the mega-drought. The volcano-prolonged drought is associated with the failure of EASM, which is directly caused by the decreasing of land-ocean thermal contrast after volcanic eruption, and indirectly influenced by negative soil moisture feedback as well as weakening and eastward retreating of West Pacific Subtropical High (WPSH).

Monsoon rainfall proxy records show clear millennial variations corresponding to abrupt climate events in Greenland ice cores during Marine Isotope Stage 3 (MIS3). The occurrence of these abrupt climate changes is associated with Atlantic Meridio-nal Overturning Circulation (AMOC) strength variations which greatly impact the global oceanic energy transport. Hence, the AMOC most likely plays a key role in modulating the global monsoon rainfall at millennial time scale. No modeling work has hitherto investigated the global monsoon system response to AMOC changes under a MIS3 background climate. Using a coupled climate model CCSM3, we simu-lated MIS3 climate using true 38 ka before present boundary conditions and per-formed a set of freshwater hosing/extraction experiments. We show not only agreement between modeling results and proxies of monsoon rainfall within global monsoon domain but also highlights a nonlinear relationship between AMOC strength and annual mean global monsoon precipitation related to oceanic heat transport constraints. During MIS3, a weakened AMOC could lead to an increase of annual mean global monsoon rainfall dominated by the southern hemisphere, whereas northern hemisphere monsoon rainfall decreases. Above about 16 Sverdrups a further strengthening of the AMOC has no significant impact on hemi-spheric and global monsoon domain annual mean rainfall. The seasonal monsoon rainfall showed same asymmetric response like annual mean both hemispherical and globally.

How the Pacific Decadal Variability (PDV) would change under a warming world remains an issue of scientific debate and societal concern. Here we show that the PDV has been experiencing an unprecedented change in the last two decades. The PDV has amplified along the west coast of North America and equatorial central Pacific while weakened over the South Pacific and Kuroshio-Oyashio Extension (KOE) region. Examination of 33 CMIP6 models’ ensemble mean projection reveals that anthropogenic radiative forcing may weaken the PDV variability in the South Pacific and KOE region, suggesting part of the observed change may be attributed to anthropogenic forcing. However, the recently increased decadal variability over the western North American coast and equatorial central Pacific may be part of the internal variability arising from increased coupling between the positive Pacific Decadal Oscillation (PDO) and negative North Pacific Gyre Oscillation (NPGO).