Ansari et al. (2025) Global assessment of aerosol radiative effects: New insights from observations, reanalysis, and climate models

Identification

• Journal: The Science of The Total Environment
• Year: 2025
• Date: 2025-11-10
• Authors: Kamran Ansari, S. Ramachandran, Ribu Cherian
• DOI: 10.1016/j.scitotenv.2025.180871

Research Groups

• Physical Research Laboratory, Ahmedabad, India
• Indian Institute of Technology Gandhinagar, Gandhinagar, India
• Sathyabama Institute of Science and Technology, Chennai, India

Short Summary

This study provides a global assessment of aerosol direct radiative effects (DRE) using multi-source data, revealing that DRE and atmospheric heating rates are highest over South Asia due to high aerosol optical depth and low single scattering albedo, while also quantifying significant biases in reanalysis and climate models.

Objective

• To conduct an integrated global assessment of aerosol optical and radiative properties using multi-source (ground-based, satellite, reanalysis, and climate model) data and quantify biases in reanalysis and climate models on regional and temporal scales to reduce uncertainty in present-day radiative forcing.

Study Configuration

• Spatial Scale: Global, with a focus on regional variations (e.g., South Asia, Australia, North America, Europe, South and Southeast Asia).
• Temporal Scale: Present-day, with analysis of spatiotemporal variations.

Methodology and Data

• Models used: Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA-2), Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations.
• Data sources: AErosol RObotic NETwork (AERONET), MODerate resolution Imaging Spectroradiometer (MODIS), Ozone Monitoring Instrument (OMI), Clouds and the Earth’s Radiant Energy System (CERES), MERRA-2, CMIP6 datasets.

Main Results

• Aerosol direct radiative effect (DRE) is highest over South Asia and lowest over Australia, followed by North America and Europe.
• Over South Asia, AERONET retrieved DRE at the surface (DRESFC) is approximately -70 W m⁻², top-of-atmosphere cooling (DRETOA) is approximately -30 W m⁻², and atmospheric heating (DREATM) is approximately 40 W m⁻² with a heating rate (HR) of approximately 0.80 K day⁻¹.
• These strong DRE values in South Asia are attributed to high aerosol optical depth (AOD: ~0.57) and low single scattering albedo (SSA: ~0.91).
• AOD and DRE (absolute) in North America, Europe, and Australia are approximately 2–4 times lower than in Asia, with less spatiotemporal variability.
• Low SSA enhances both atmospheric heating and surface cooling efficiencies over South Asia and biomass-burning regions.
• MERRA-2 underestimates DRE globally, with the largest bias (~33 %) over South Asia, primarily due to significant underestimation of MERRA-2 AOD in high AOD conditions.
• MERRA-2 DRE shows better agreement with AERONET DRE than with CERES retrieved DRE.
• The CMIP6 multi-model mean underestimates AOD by approximately 1.4 times over South and Southeast Asia.

Contributions

• First-of-its-kind comprehensive global assessment of aerosol direct radiative effects using an integrated analysis of multi-source (ground-based, satellite, reanalysis, and climate model) data.
• Quantifies regional and temporal biases in MERRA-2 reanalysis and CMIP6 climate models against observational data for aerosol optical and radiative properties.
• Provides new insights into the spatial distribution and drivers of aerosol DRE, particularly highlighting the strong effects over South Asia due to specific aerosol properties.

Funding

Not specified in the provided text.

Citation

@article{Ansari2025Global,
  author = {Ansari, Kamran and Ramachandran, S. and Cherian, Ribu},
  title = {Global assessment of aerosol radiative effects: New insights from observations, reanalysis, and climate models},
  journal = {The Science of The Total Environment},
  year = {2025},
  doi = {10.1016/j.scitotenv.2025.180871},
  url = {https://doi.org/10.1016/j.scitotenv.2025.180871}
}