In the intricate web of Earth’s climate, atmospheric aerosols wield a power that often escapes full comprehension. These tiny particles suspended in the atmosphere influence the planet’s energy balance by interacting with sunlight and clouds, and yet they remain one of the largest sources of uncertainty in climate change projections. A recent study sheds new light on this puzzle by focusing on a unique region where smoke aerosols from African biomass burning hover above persistent low-lying clouds over the southeast Atlantic Ocean. The findings reveal that previous climate models may have significantly underestimated the warming effect of aerosols in this region by ignoring the daily fluctuations of cloud cover — a revelation with profound implications for climate science.
Aerosols play a dual role in the climate system: they can cool the Earth by reflecting sunlight back into space or warm it by absorbing solar radiation. Over the southeast Atlantic, a massive plume of light-absorbing smoke travels from fires in central and southern Africa, settling above stratocumulus clouds that blanket the ocean below. This layering creates a complex environment where the aerosols’ ability to absorb radiation directly contributes to atmospheric warming, yet the magnitude of this warming remains contentious among scientists. The direct aerosol radiative effect (DARE) captures this warming by quantifying how much sunlight the aerosols intercept and transform into heat.
Climate models have traditionally struggled to capture the true strength of DARE in this region, showing a wide range of estimates. This discrepancy limits our confidence in predicting regional and global climate responses driven by aerosol-cloud interactions. One often overlooked factor is the diurnal, or daily, cycle of low clouds—how cloud cover and thickness evolve throughout the day. Satellite observations frequently focus on a snapshot during early afternoon hours when clouds tend to be less extensive and thinner. However, the latest research utilizes hourly satellite data to track these cloud changes through the entire day and incorporate them into radiative transfer models that calculate aerosol warming more accurately.
By examining satellite measurements between 20° South and the equator, spanning from 10° West to 15° East, researchers were able to disentangle the relationship between cloud dynamics and aerosol radiative effects. Their approach reveals that when the full diurnal range of cloud coverage and optical depth—how thick or thin the clouds are—is included, the estimated regional aerosol warming more than doubles. This increase corresponds to an additional +1.7 ± 0.4 watts per square meter of atmospheric warming compared to estimates that assume static afternoon cloud conditions. Such a difference is not trivial; it has the potential to reshape how scientists evaluate the climate forcing of aerosols in global models.
What drives this amplified aerosol warming is the predominance of thicker and more extensive cloud decks during the morning hours. At these times, the stratocumulus clouds are at their peak, providing an ideal “reflective backdrop” for aerosols to absorb sunlight effectively. This vertical configuration maximizes the so-called semi-direct effect, where smoke aerosols heat the air above clouds and modify cloud properties themselves, affecting precipitation and cloud longevity. Previous studies that neglected these morning features inadvertently underestimated the warming influence of aerosols, skewing regional climate forcing assessments.
Understanding the intricate dance between clouds and aerosols is critical because the southeast Atlantic represents one of the most significant natural laboratories for studying aerosol-climate interactions. Given the vast extent of smoke plumes produced seasonally by African fires and the stable cloud formations over the ocean, this region exemplifies how aerosols can warm the atmosphere above clouds while simultaneously affecting cloud behavior itself. Fine-tuning our estimates of aerosol radiative impacts here not only clarifies regional climate feedbacks but also feeds into global climate projections, where these aerosols and their indirect effects remain dominant sources of model uncertainty.
The research emphasizes that current climate models need to incorporate observed cloud diurnal cycles to produce more realistic simulations of the aerosol direct radiative effect. Ignoring these adjustments leads to systemic biases that veer toward an underestimation of aerosol-induced warming. This realization carries important consequences for climate mitigation strategies and policy-making, as the underestimated warming may mask the true severity of aerosol contributions to regional and global energy budgets.
To achieve these insights, the scientists leveraged state-of-the-art radiative transfer modeling techniques combined with high temporal resolution satellite data from instruments capable of detecting both aerosol optical properties and cloud dynamics hourly. This approach surpasses traditional methodologies that rely on single daily snapshots, ultimately revealing diurnal variations in cloud fraction and optical depth as decisive factors controlling the intensity of aerosol warming. By capturing the full daily rhythm of the cloud-aerosol system, these models promise to reduce uncertainties that have long impeded aerosol climate science.
Moreover, this enhanced understanding sheds light on feedback mechanisms that challenge conventional thinking about aerosol-cloud interactions. For example, during the morning hours, increased cloud cover under smoke layers intensifies aerosol absorption, which could warm the atmospheric column and potentially change cloud properties in ways not fully captured by models assuming static cloud fields. Such feedback loops illustrate the delicate balance of processes governing Earth’s radiation budget and highlight the need for continuous monitoring and modeling innovations.
The study’s findings urge the scientific community to revisit past evaluations of aerosol climatic effects and reconsider how cloud diurnal cycles have been treated in previous assessments. By integrating high-resolution satellite observations into climate models, researchers can better quantify the direct radiative forcing from aerosols and thereby constrain the wide disparities observed between different global climate models. This refinement is not merely an academic improvement; it directly influences the accuracy of climate sensitivity predictions and informs future projections critical for adaptation and mitigation planning.
Furthermore, the southeast Atlantic region serves as a key testing ground for new satellite missions and remote sensing techniques designed to capture aerosol-cloud interactions with unparalleled precision. As observational technologies advance, these capabilities will allow scientists to scrutinize the processes identified in this study across different seasons and atmospheric conditions, enabling a comprehensive picture of how aerosols impact climate dynamics regionally and globally.
This landmark research underscores the importance of coupling observational data with sophisticated modeling frameworks to unravel the complexities of the Earth’s climate system. The enhanced aerosol warming over the southeast Atlantic linked to the cloud diurnal cycle challenges assumptions embedded in many current climate datasets and calls for a paradigm shift in how aerosol-cloud radiative effects are represented. Such a shift is indispensable for resolving one of the most persistent uncertainties in climate prediction literature.
In a broader context, these insights highlight how seemingly subtle atmospheric phenomena like the timing and thickness of low-lying clouds can cascade into significant changes in the Earth’s energy balance. They remind us that the climate system operates with interconnected feedbacks that demand detailed and temporally resolved observations to decode. As society grapples with anthropogenic climate change, accurate assessment of all forcings—including natural and anthropogenic aerosols—will be crucial for policy-relevant climate projections.
Ultimately, this research adds a crucial piece to the challenging mosaic of climate science, demonstrating that daily rhythms in cloud cover are not just meteorological curiosities but powerful modulators of aerosol radiative impacts. Future climate models that incorporate these diurnal variations stand to offer more reliable forecasts, reduce uncertainty margins, and guide effective responses to the ongoing challenges posed by global warming.
In summary, the southeast Atlantic’s atmospheric dynamics reveal that the aerosol warming effect has been greatly underestimated due to inadequate consideration of cloud diurnal cycles. By leveraging hourly satellite measurements and advanced radiative transfer modeling, the study offers a compelling case for revised climate modeling practices that embrace the full complexity of aerosol-cloud interactions. This sophisticated and timely contribution emphasizes how refined observations can illuminate the hidden drivers of climate variability and advance the predictive capabilities essential for navigating the uncertain future of our planet.
Subject of Research: Atmospheric aerosols and cloud diurnal cycle impacts on regional direct aerosol radiative effect (DARE) over the southeast Atlantic Ocean.
Article Title: Regional aerosol warming enhanced by the diurnal cycle of low cloud.
Article References:
Chang, I., Gao, L., Adebiyi, A.A. et al. Regional aerosol warming enhanced by the diurnal cycle of low cloud.
Nat. Geosci. (2025). https://doi.org/10.1038/s41561-025-01740-1
Image Credits: AI Generated
