Accelerated Warming Shifts the Balance Between Thermodynamic Moistening and ENSO-related Variability in Atmospheric Water Vapour

Abstract. Atmospheric water vapour is shaped by both sustained global warming (GW) and El Niño–Southern Oscillation (ENSO), but how these two climate influences are expressed in the water-vapour field and how their coupling changes under accelerated warming remain poorly quantified. Here we comprehensively characterize the links between global GNSS-derived precipitable water vapour (PWV), a vertically integrated measure of atmospheric moisture, and both GW and ENSO by integrating Independent Component Analysis (ICA) and Convergent Cross Mapping (CCM). Warming-related and ENSO-related PWV signals are extracted from the GNSS PWV field using ICA and are denoted as PWV_GW and PWV_ENSO, respectively. PWV_GW is closely associated with GW (r = 0.79), and CCM supports dominant GW → PWV_GW coupling. By contrast, PWV_ENSO responds to ENSO with an approximately 12-month lag (r = 0.77), and extended CCM indicates bidirectional coupling between ENSO and PWV_ENSO. After the transition to accelerated warming around 2013, the sensitivity of PWV_GW to temperature increases markedly, consistent with enhanced thermodynamic moistening. At the same time, the ENSO → PWV_ENSO coupling weakens despite stronger ENSO variability. These findings suggest that accelerated warming shifts the balance between long-term thermodynamic moistening and interannual ENSO-related variability in the atmospheric water vapour field.