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Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal
Steven Ghan1, Minghuai Wang2, Shipeng Zhang3
1Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99352; Steve.Ghan@pnnl.gov.
Summary
Understanding aerosol impacts on cloud radiative forcing is complex. Recent variability data poorly constrains preindustrial estimates, necessitating new methods to accurately assess anthropogenic aerosol effects on climate.
Area of Science:
- Atmospheric Science
- Climate Science
- Aerosol Science
Background:
- Aerosols significantly influence cloud radiative forcing through complex processes.
- Key relationships link emissions to cloud properties and radiative effects.
Purpose of the Study:
- To evaluate the reliability of using recent aerosol variability to infer preindustrial aerosol impacts on cloud radiative forcing.
- To identify limitations in current models and observational constraints.
Main Methods:
- Analysis of Aerosol Comparisons between Observations and Models (AeroCom) simulations.
- Examination of relationships between aerosol precursor gases, cloud condensation nuclei (CCN), droplet number, cloud properties, and radiative forcing.
- Comparison of relationships derived from recent variability versus anthropogenic change.
Main Results:
- Relationships derived from recent spatial/temporal variability are often poor constraints for preindustrial to present-day anthropogenic changes.
- Sign of some aerosol-cloud relationships can differ regionally between recent variability and anthropogenic change.
- Current methods may inaccurately represent aerosol impacts on cloud radiative forcing.
Conclusions:
- Recent variability is an insufficient proxy for constraining preindustrial aerosol-cloud-radiation interactions.
- New approaches, such as sustained measurements in changing emission regions or improved proxies, are crucial.
- Accurate estimation of anthropogenic aerosol impacts on climate requires better constrained relationships.
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