1 Introduction

In recent years, ocean decadal variability has attracted ever-increasing attention for its importance in modulating global warming (England et al. 2014; Bordbar et al. 2017). In its sixth assessment report (AR6), the Intergovernmental Panel on Climate Change (IPCC) clearly affirmed the significant contribution of human activity to the warming of the atmosphere, oceans, and land by increasing carbon dioxide (CO2) emissions since the Industrial Revolution (Li 2022; Thapliyal et al. 2023). However, the increase in global mean surface temperature (GMST) is not linear but instead has two alternating phases, which include accelerated warming and a global warming hiatus (IPCC, 2013). GMST increased rapidly during 1920–1945 and 1977–2000 but stalled during 1946–1976 and 2001–2013 (England et al. 2014, 2015; Bordbar et al. 2019). The common view is that greenhouse gases and anthropogenic aerosols dominate long-term warming trends, while natural internal variability determines the climate system phase shift (Farneti 2017). By conducting the pacemaker experiments, it was suggested that the global warming hiatus may be caused by the negative phase of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Variability (AMV) (Kosaka and ** rate (Wu and Liu 2020). This result is established in the mid-high latitudes, and the tropical atmosphere forcing seems to change little under global warming (Fig. S15e–h). The shortened period is caused by the acceleration of ocean Rossby waves (Fang et al. 2014) which is also different in the equatorial regions.

Overall, under global warming, the shortening and weakening of the decadal variabilities are both robust across the global regions in CMIP6 models. And the shortening of periods is also established in the CESM large ensemble with longer data length (180 years) (Fig. S16). However, the TPDV has a weaker response which might be related to the tropical atmospheric forcing. And the pattern of the decadal variabilities will not change in the future, which suggests the dynamical process may not change under global warming. However, the expression outside the chosen regions of each decadal variability is weakened in the future scenarios (Figs. S14), which could be related to the change of teleconnection between different regions or the industrial aerosols or greenhouse gases forcing signal in decadal variabilities indices (Baek et al. 2022). In this study, we provide an overview of the responses of global ocean decadal variability in the future. Further studies are needed to verify these results by using longer data and understanding the mechanism in different regions.