The causes of ENSO diversity, although being of great interest in recent research, do not have a consistent explanation. This study provides a possible mechanism focused on the background change of the tropical Pacific as a response to global warming. The second empirical orthogonal function mode of the sea surface temperature anomalies (SSTA) in the tropical Pacific, namely the cold tongue mode (CTM), represents the background change of the tropical Pacific under global warming. Using composite analysis with surface observations and subsurface ocean assimilation data sets, we find ENSO spatial structure diversity is closely associated with the CTM. A positive CTM tends to cool the SST in the eastern equatorial Pacific and warm the SST outside, as well as widen (narrow) zonal and meridional scales for El Niño (La Niña), and vice versa. Particularly in the positive CTM phase, the air‐sea action center of El Niño moves west, resembling the spatial pattern of CP‐El Niño. This westward shift of center is related to the weakened Bjerknes feedback (BF) intensity by the CTM. By suppressing the SSTA growth of El Niño in the eastern equatorial Pacific, the CTM contributes to more frequent occurrence of CP‐El Niño under global warming.

The high aerosol concentration (AC) over eastern China has attracted attention from both science and society. Based on the simulations of a chemical transport model using a fixed emissions level, the possible impact of the previous autumn North Atlantic Oscillation (NAO) combined with the simultaneous El Niño–Southern Oscillation (ENSO) on the boreal winter AC over eastern China is investigated. We find that the NAO only manifests its negative impacts on the AC during its negative phase over central China, and a significant positive influence on the distribution of AC is observed over south China only during the warm events of ENSO. The impact of the previous NAO on the AC occurs via an anomalous sea surface temperature tripole pattern by which a teleconnection wave train is induced that results in anomalous convergence over central China. In contrast, the occurrence of ENSO events may induce an anomalous shift in the western Pacific subtropical high and result in anomalous southwesterlies over south China. The anomalous circulations associated with a negative NAO and El Niño are not favorable for the transport of AC and correspond to worsening air conditions over central and south China. The results highlight the fact that the combined effects of tropical and extratropical systems play a considerable role in affecting the boreal winter AC over eastern China.

The potential influence of El Niño Modoki event 1994/1995 on tropospheric aerosol concentrations was investigated for southern China using the GEOS‐Chem model with meteorological data collected from 1986 to 2006. The results suggest that aerosol concentrations increase during mature phases of El Niño Modoki event 1994/1995 (boreal winter) and decrease during decay phases (boreal spring, summer, and autumn). Aerosol concentrations anomalies were found to be due to circulation changes associated with El Niño Modoki, whereby both the horizontal and vertical transport of aerosol mass fluxes determined the pattern of aerosol concentrations associated with the event. In contrast, the role of wet deposition appeared to be limited. Furthermore, these results suggest that the amplitude of anomalous aerosol concentrations associated with El Niño Modoki event 1994/1995 have the potential to reach approximately 30% of the climatological mean, indicating that El Niño Modoki plays an important role in influencing aerosol concentrations over southern China.

The recent intensification of trade winds over the tropical Pacific is the strongest ever observed in the past hundred years. This strengthening trend is of great interest in recent research, but the causes are still unclear. Using two relatively long‐term surface wind data sets, the present research shows that there is an overall strengthening trend of the trades in the western equatorial Pacific and an overall weakening trend in the eastern equatorial Pacific. This long‐term trend pattern can be primarily attributed to the cold tongue mode (CTM) rather than to the impact of El Niño–Southern Oscillation (ENSO), El Niño Modoki, or Interdecadal Pacific Oscillation (IPO). The CTM, the second empirical orthogonal function mode of the sea surface temperature anomalies (SSTA) in the tropical Pacific, represents a strong long‐term trend of tropical Pacific background state under global warming. According to the Gill‐Matsuno theory, the easterly winds over the western equatorial Pacific are induced by the equatorial Pacific cooling and warming SSTA associated with the CTM, while the westerly winds over the eastern equatorial Pacific is primarily due to the eastern equatorial Pacific cooling SSTA associated with the CTM. Ultimately, an alternative explanation of past and future changes of the trades is expected to lead to improved understanding of the global climatic impacts of the enhanced trades in tropical Pacific under global warming.

El Niño‐Southern Oscillation (ENSO) triggers variations of the global Hadley circulation (HC), while the latter may potentially feedback to ENSO events. Previous studies mainly investigated the interactions between ENSO and the global zonal‐mean HC. Here, we present a regional perspective of HC variability by introducing zonal variations. Results show that El Niño intensifies the regional HC over the central‐eastern Pacific, while weakening the regional HC over both the Indo‐Pacific warm pool and the tropical Atlantic. The background seasonal cycle modulates the equatorial‐asymmetric component of HC, with an anticlockwise (clockwise) asymmetric circulation over the central equatorial Pacific before (after) El Niño peaks. Remarkably, the asymmetric HC in boreal spring leads ENSO with a lead correlation of up to 0.68, mediated by the wind‐evaporation‐sea surface temperature (SST) feedback and other atmosphere‐ocean dynamics. The antecedent HC anomaly may contribute to ENSO predictability.

Global climate variability has been linked with some of the largest dengue outbreaks, including the record-breaking 2023–2024 epidemic, but the understanding of their mechanism and evidence for their association is lacking. By incorporating reported dengue cases and climate data from 57 countries across the Americas and Asia from 1980 to 2024, we unpacked the global climate teleconnection and quantifying its impact on dengue cases. We revealed that the heterogeneity in the association between global climate variability and dengue cases across regions is affected by the strength and types of global climate teleconnections with temperature and precipitation. By controlling for the heterogeneity, 63% of the variation in dengue cases can be attributed to El Niño–Southern Oscillation fluctuations, with higher values in endemic regions. The 1982–83, 1997–98, 2015–16, and 2023–24 El Niño events were estimated to have induced an additional 0.2, 1.4, 4.1, and 9.6 million dengue cases, respectively, over regular seasonal patterns. Due to human-induced warming, El Niño events and teleconnections may cause a 39.0–81.7% increase in cumulative cases in 2020–2099. Our findings quantify the association between global climate variability and dengue epidemics and caution about the potential future risk.