Cai, W., C. Reason, E. Mohino, B. Rodríguez de Fonseca, J. Malherbe, A. Santoso, X. Li,
H. Chikoore, H. C. Nnamchi, M. J. McPhaden, N. Keenlyside, A. Taschetto, L. Wu, B.
Ng, Y. Liu, T. Geng, K. Yang, G. Wang, F. Jia, X. Lin, S. Li, Y. Yan, J. Wang, L. Zhang,
Z. Li, W. Pokam, L Zhou, X. Zhang, F. Engelbrecht (2025). Impact of El Niño-Southern
Oscillation on African climate. Nature Reviews Earth & Environment. 6, 503520.
https://doi.org/10.1038/s43017-025-00705-7.

Abstract:
The El Niño–Southern Oscillation (ENSO) — describing shifts between warm El Niño and cold La Niña phases — has a substantial effect on the global climate. In this Review, we outline the mechanisms and climate impacts of ENSO in Africa, focusing on rainfall. ENSO’s influence varies strongly by season, region, phase, event and decade, highlighting complex dynamics and asymmetries. Although difficult to generalize, key characteristics include: anomalies across the Sahel in July–September, related to the tropospheric temperature mechanism; a strong dipole in anomalies between eastern and southern Africa during October–December (the short rain reason) and December–February, linked to interactions with the Indian Ocean Dipole and Indian Ocean Basin mode, respectively; and anomalies over southern Africa (with possible indications of opposite anomalies over East Africa) during March–May (the long rain season), associated with continuation of the Indian Ocean Basin mode. These teleconnections tend to be most pronounced for East Pacific El Niño and Central Pacific La Niña events, as well as during decades when interbasin interactions are strongest. Although challenging to simulate, climate models suggest that these impacts will strengthen in the future, manifesting as an increased frequency of ENSO-related dry and wet extremes. Given the reliance of much of Africa on rain-fed agriculture, resolving these relationships is vital, necessitating realistic simulation of regional circulations, ENSO and its interbasin interactions.

Liu, Y., M. J. McPhaden, W. Cai, Y. Zhang, J. Zhao, H. C. Nnamchi, X. Lin, Z. Li, J-.Y. Yang (2025). Basin-wide and coastal modes of north tropical Atlantic variability have distinct impacts onhurricanes. Communications Earth & Environment. 6, 549. doi.org/10.1038/s43247-025-02529-1.

Abstract:
Warm sea surface temperature anomalies in the north tropical Atlantic are conducive to increased intensity and frequency of Atlantic hurricanes. The period 2023-2024 saw two consecutive warm events but with distinct anomaly patterns. Here we use observations and model outputs over the past several decades to determine whether there exists inherent diversity in north tropical Atlantic surface temperature spatial structures and impacts. We find two distinctive modes of variability: a basin-wide mode and a coastal mode, underpinned by differing relationships between air-sea heat flux and sea surface temperature anomalies. The basin-wide mode has a stronger influence on Atlantic hurricane activity due to its more westward and persistent anomaly pattern. Since the 1990s, the well-known impact from El Niño-Southern Oscillation on the north tropical Atlantic is felt through its influence on the basin-wide mode. Our results highlight the importance of distinguishing the two distinctive modes in assessing and predicting their impacts.

Tian, Q., J.-Y. Yu, H. C. Nnamchi, T. Li, J. Li, L. Zhang, X. Li (2025). Unraveling the mystery of recent shortened response time of ENSO to Atlantic forcing. Nature Communications. 16, 5884. https://doi.org/10.1038/s41467-025-61130-4

Abstract:
The El Niño-Southern Oscillation (ENSO) is known to respond to tropical Atlantic (TA) sea surface temperature (SST) forcing. However, the response time of ENSO to the TA SST forcing is not stationary but varies over decades, the reasons for which remain poorly understood. Here we show that decadal changes in ENSO’s response time to TA SST forcing are primarily influenced by the south-north shift of the dominant mode of TA SST variability itself. Before the mid-1980s, the southward-shifted TA mode prolongs the response time to ~20 months through an eastward-propagating mid-latitude teleconnection. In contrast, when the TA mode shifts northward after the mid-1980s, the response time decreases to 6–9 months via a faster westward-propagating subtropical teleconnection. Our findings underscore the importance of considering the meridional shift of the TA mode when understanding the impacts of the TA SST variability on ENSO, which has profound implications for ENSO forecasting.

Nnamchi, H.C., Latif, M. Predictable equatorial Atlantic variability from atmospheric convection-ocean coupling. npj Clim Atmos Sci 8, 149 (2025). https://doi.org/10.1038/s41612-025-01041-9

Abstract:
The Atlantic Niño exerts profound impacts on regional and global atmospheric circulation and climate, and on equatorial Atlantic biogeochemistry and ecosystems. However, the mode’s prediction remains a challenge which has been partly attributed to weak atmosphere-ocean coupling in the region. Here we introduce a framework that enhances the detection of the coupling between meridional migrations of atmospheric deep convection and zonal thermocline feedback. This approach reveals high predictive skill in a 196-member seasonal prediction ensemble, demonstrating robust predictability at 1–5-month forecast initialization lead times. The coupled mode is strongly correlated with land-precipitation variability across the tropics. The predictive skill largely originates in the Atlantic Ocean and is uncorrelated with El Niño Southern Oscillation in the Pacific, the leading mode of interannual climate variability globally. These skillful predictions raise hopes for enabled action in advance to avoid the most severe societal impacts in the affected countries.

Tank, L., Voget-Kleschin, L., Garschagen, M., Boettcher, M.,  Mengis, N., Holland-Cunz, A., Rehder, G., and  Baatz, C. (2025) "Distinguish between feasibility and desirability when assessing climate response options." npj Climate Action 4, 34. https://doi.org/10.1038/s44168-025-00237-2

Abstract:
The current literature on assessing climate change response options does not sufficiently distinguish between assessing options in terms of their feasibility and in terms of their desirability. One example of this is the IPCC feasibility assessment framework. We argue that assessments of climate response options should indeed cover questions of desirability, but they should do so explicitly. Transparency about underlying normative standards is the key to a productive desirability assessment.

Huo, W., Spiegl, T., Wahl, S., Matthes, K., Langematz, U., Pohlmann, H., Kröger, J. (2025) "Assessment of the 11-year solar cycle signals in the middle atmosphere during boreal winter with multiple-model ensemble simulations." Atmospheric Chemistry and Physics, 25 (4), 2589–2612, https://doi.org/10.5194/acp-25-2589-2025

Summary:
To better understand possible reasons for the diverse modeling results and large discrepancies of the detected solar fingerprints, we took one step back and assessed the “initial” solar signals in the middle atmosphere based on a set of ensemble historical simulations with multiple climate models – the Flexible Ocean Climate Infrastructure (FOCI), the ECHAM/MESSy Atmospheric Chemistry (EMAC), and the Max Planck Institute for Meteorology Earth System Model in high-resolution configuration (MPI-ESM-HR). Consistent with previous work, we find that the 11-year solar cycle signals in the shortwave heating rate (SWHR) and ozone anomalies are robust and statistically significant in all three models. These initial solar cycle signals in the SWHR, ozone, and temperature anomalies are sensitive to the strength of the solar forcing. Correlation coefficients of the solar cycle with the SWHR, ozone, and temperature anomalies linearly increase along with the enhancement of the solar cycle amplitude. This reliance becomes more complex when the solar cycle amplitude – indicated by the standard deviation of the December–January–February mean F10.7 – is larger than 40. In addition, the cold bias in the tropical stratopause of EMAC dampens the subsequent results of the initial solar signal. The warm pole bias in MPI-ESM-HR leads to a weak polar night jet (PNJ), which may limit the top-down propagation of the initial solar signal. Although FOCI simulated a so-called top-down response as revealed in previous studies in a period with large solar cycle amplitudes, its warm bias in the tropical upper stratosphere results in a positive bias in PNJ and can lead to a “reversed” response in some extreme cases. We suggest a careful interpretation of the single model result and further re-examination of the solar signal based on more climate models.

M207 expedition on the RV METEOR took a place from January 4 to February 11, 2025, from Belem, Brazil to Mindelo, Cabo Verde.

The EXPORT is the part of the WARD Tropics expedition, which focused on the trans-Atlantic transport of mineral dust. With this aim the new portable meteorological observatory for desert-dust transport was installed on board of the ship. Dust particles can affect climate in many different ways, from affecting radiative forcing to playing a role of nutrient supplier. During the expedition we had an opportunity to measure the Saharan dust, transported far away from the source along tropical Atlantic. Several instruments were installed on board of METEOR, like ceilometer, flat plate aerosol sampler, high volume sampler, disdrometer, solar radiation measurement station and also different sun photometers to record the aerosol optical depth were used.

neue Veröffentlichung:

Mu, F., Fiedler, S. How much do atmospheric depressions and Mongolian cyclones contribute to spring dust activities in East Asia?. npj Clim Atmos Sci 8, 51 (2025). doi.org/10.1038/s41612-025-00929-w

Summary:
Severe East Asian dust storms occur in spring due to dust-emitting winds in the Gobi Desert associated with Mongolian cyclones. The present study performs the first quantitative assessment of the contributions of Mongolian cyclones to springtime dust activity in East Asia, based on multiple reanalyses and observational datasets for 2001–2022. Atmospheric depressions dominate dust activities in Northern China, explaining ~90–92% of the total dust emissions in the Gobi Desert and ~88–93% of the dust aerosol optical depth (τ) downwind, depending on the dataset. Mongolian cyclones, defined as long-living and mobile atmospheric depressions, explain almost half (~34–47%) of the Gobi’s total dust emissions and τ downwind, and are the primary driver of high-impact dust storms. The number of Mongolian cyclones, along with the dust activity, has decreased since 2001, with a spatial pattern of the dust emission trend that is consistent with the northward shift of cyclone tracks.