From Irfan Muhammed
Seminar 24 (July 29, 2026) of the CleanCloud series.
Natural aerosols are the main contributors to the total atmospheric aerosol burden. Their characteristics vary widely, depending on their source region and the atmospheric aging they undergo during transport. These aging processes can alter key aerosol properties that influence cloud formation, radiative properties, air quality, toxicity, and ecosystem throughout the globe. However, the consequences of interactions between natural aerosols and other pollutants during aging remain inconclusive. Within the CleanCloud PIANO campaign, we investigated how atmospheric aging affects the climate and health impacts of natural aerosols. Chamber experiments were conducted using Mediterranean Sea water and dust samples from many parts of the world to generate aerosols, which were then exposed to acidic gases under controlled conditions. The resulting changes were evaluated through measurements of oxidative potential (OP), an indicator of the ability of particles to generate oxidative stress, and ice nucleation activity (INA), a key parameter controlling cloud formation, structure, and precipitation processes.Our results show that atmospheric processing can significantly modify both the health-relevant and climate-relevant properties of aerosols. Acidification alters particle chemistry, influencing metal solubility and oxidative potential, while also affecting the ability of particles to act as ice-nucleating particles.
Seminar 24 (July 29, 2026) of the CleanCloud series.
Multi-satellite constraints from PACE and EarthCare reduce uncertainty in modeled aerosol forcing
Abstract:Aerosol interactions with radiation and clouds remain a dominant source of uncertainty in estimates of human influence on climate, limiting confidence in historical climate attribution and future projections. A challenge in attempts to reduce this uncertainty with observations is to match multiple aerosols and clouds at different locations and times simultaneously. Here, we use observations from the recently launched PACE and EarthCARE satellites of aerosol amount, size, absorption, and vertical distribution, together with Cloud Droplet Number Concentration, to constrain the Aerosol Effective Radiative Forcing (ERF) in aerosol-climate model simulations using a perturbed parameter ensemble. We show that the combined use of the observations constrains natural and anthropogenic emissions, physical aerosol properties, and processes, resulting in a reduction of ERF parametric uncertainty by 34%. ERF๐๐๐ and ERF๐๐๐ uncertainty credible interval ranges are reduced by 66% and 32%, respectively. We find an observation-consistent ERF of -1.52 [-2 to -1.1] W mโ2, which suggests stronger aerosol cooling than the current IPCC estimate of -1.3 [-2.0 to -0.6] W mโ2.