Nnamchi, H.C., Fiedler, S. Anthropogenic aerosols override greenhouse gases in Sahel climate change. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03474-3

Abstract:
Climate change has intensified weather extremes in the semi-arid Sahel, one of the world’s most vulnerable regions. However, the cause of the most dramatic changes, from the Sahel droughts of the 1970s and 1980s to wetter conditions in recent decades, remains contested. Here we use ensembles of climate model simulations to show that these changes were primarily driven by anthropogenic aerosols. Aerosol-induced slowdown of the Hadley Cell, the atmospheric circulation that drives tropical convection globally, caused the droughts. The subsequent reduction of aerosol emissions over the North Atlantic land regions enhanced meridional heating gradient, convection, and rainfall over the Sahel. Conversely, the impact of greenhouse gases is markedly weaker, 3.5 to 5.3 times less than that of aerosols. The discovery of a dominant role for the aerosol-induced heating gradient, rather than absolute concentrations, provides a framework for advancing regional climate risk assessments generally.

Abstract:
Aerosols have played an important role in defining the climate over the historical period, due to their net cooling effect in the atmosphere. However, as their emissions are expected to decrease in upcoming decades, they will be associated with reduced cooling, i.e. future warming, of the planet. Despite their importance and high uncertainty associated with their radiative forcing, aerosols inclusion in simple climate models, impact models and carbon-based climate assessment metrics requires simplifications and assumptions. Typically, interactions between physical and biogeochemical processes are disregarded by such. By varying the spatial implementation of aerosols in an intermediate complexity model we explore the variability in Earth system responses under an ambitious mitigation scenario due to aerosols-radiation interactions. When aerosols are implemented disregarding their spatial distribution, surface air temperature is higher by almost 0.1 °C when compared to a regionally heterogeneous implementation, corresponding to an uncertainty of ca. 200 GtCO₂ of remaining carbon budgets. The main processes driving these responses are the land surface temperature and its effect on soil respiration, as well as changed ocean heat fluxes due to differences in incoming shortwave radiation at the surface. The spatial distribution of aerosols triggers important climate-carbon feedbacks, which should be specifically considered when assessing climate evolution and simulated Earth system responses. Even if aerosol-cloud interactions aren’t explored, the results already indicate that aerosols should be deliberately accounted for in simple models and assessment tools, as their triggered feedbacks will be instrumental in defining pathways for temperature stabilisation and evaluating, for example, remaining carbon budgets.

Rodriguez-Fonseca, B., R. Rodrigues, I. Polo-Sánchez, M. Martín-Rey, T. Losada, J. L. Parages, I. Gómara, L. Shannon, E. Exarchou, N. Keenlyside, D. Rivas, E. C. Miguélez, L. M. Carramolino, F. Ramirez, C. Artana, R. Angelini, R. A. Imbol Koungue, M. Araujo, A. Bertrand, P. Brandt, W. Cai, M. Coll, L. Gammage, S. Koseki, J. Lübbecke, E. McDonagh, M. McPhaden, V. Martín-Gómez, R. Mechoso, E. Mohino, J. Muelbert, S. Ndoye, H. C. Nnamchi, J. Ramanantsoa, M. Rouault, J. C. Sánchez-Garrido, R. Schwamborn, J. Schmidt, H. Sloterdijk, J. Steenbeek, A. T. Gaye. ENSO impacts on marine ecosystems and fisheries in the tropical and South Atlantic. Nature Reviews Earth & Environment 7, 43–59 (2026). https://doi.org/10.1038/s43017-025-00742-2

Abstract:
Tropical and South Atlantic marine ecosystems support fisheries that have vital environmental and socioeconomic importance. In this Review, we outline how the El Niño–Southern Oscillation — a Pacific mode of sea surface temperature variability — influences Atlantic fisheries via teleconnections and cascading linkages between physical, biogeochemical and ecological systems. Connections are driven by tropical pathways (involving changes in atmospheric stability associated with the Walker circulation and tropospheric warming) and extratropical pathways (involving the Pacific–South American and Pacific–North American teleconnection patterns). Depending on the location, these pathways modify rainfall and river discharge, winds and upwelling, or a combination of both, impacting salinity, nutrient availability, primary production and, thus, fish recruitment, biomass and catch. Fishery responses are strongly species dependent, reflecting variations in behaviour between species to environmental factors (such as temperature, oxygen, salinity, habitat and food availability). This regional variability and species dependency, coupled with strong non-stationarity, highlights the complexity of El Niño–Southern Oscillation impacts on Atlantic marine ecosystems. This historical signal is projected to weaken in the future. Enhanced observational systems and refined ecosystem models are urgently needed to enhance predictive capabilities, reduce societal impacts and improve sustainable management in these regions.