The Madden-Julian Oscillation (MJO) (Madden & Julian, 1971;Zhang, 2005) is a convectively coupled wave system propagating eastward from the tropical Indian Ocean into the Pacific and is considered an important source of extended range predictability and, in particular, of extreme weather events (Zhang, 2013). The MJO activity over the Maritime Continent and Western Pacific effectively triggers planetary-scale waves over the mid-latitudes (Franzke et al., 2019;Stan et al., 2017), where the enhanced teleconnection patterns can even cause warm temperature anomalies over the Arctic (e.g., Kang & Tziperman, 2017;Lee et al., 2011;Yoo et al., 2011). Hence, there is a strong need to better understand how the MJO will change under the influence of global warming. Modeling studies have shown that in a warmer climate, there will be a more active MJO (e.g., Adames et al., 2017;Bui & Maloney, 2018;Maloney et al., 2019), with summer precipitation in North America likely being affected through relevant teleconnections (Zhou et al., 2020). Meanwhile, recent observational studies found that over the past decades, the MJO residence time over the Maritime Continent and the Western Pacific weakly increased, which has affected rainfall around Southeast Asia and the warming trend of the Arctic (