Simulations of anthropogenic and natural effects on aerosol-climate interactions
Title: Simulations of anthropogenic and natural effects on aerosol-climate interactions
SNIC Project: SNIC 2014/1-155
Project Type: SNAC Medium
Principal Investigator: Ilona Riipinen <>
Affiliation: Stockholms universitet
Duration: 2014-05-01 – 2015-05-01
Classification: 10501 10502 10503


The radiative effects of atmospheric aerosol particles are the largest individual uncertainty in our understanding of past, present and future climate. A large fraction of this uncertainty stems from lacking knowledge on the pre-industrial and pristine aerosol concentrations – as information on the natural aerosol emissions and their atmospheric processing is needed for accurate estimates of the human influence on atmospheric particulate matter and the Earth’s energy balance. Furthermore, information on historical aerosol loadings is important for understanding the evolution of the past climate. Changing aerosol concentrations affect land and ocean biogeochemical cycles directly, by modifying the atmospheric radiative fluxes, as well as indirectly by adding nutrients to ecosystems. While models succeed relatively well in capturing the global average temperature in the past millennium, there are still major discrepancies between climate reconstructions and present atmospheric models. The effect of atmospheric aerosols on the climate in the past centuries is highly uncertain. Studies on mineral, sulfate and sea salt aerosol concentrations exist, but any impact on aerosols due to biospheric changes is highly uncertain. Furthermore, the ways that human activities and emissions interact with the natural aerosol fraction are still largely unquantified. The overall goal of this project is to provide quantitative estimates on the evolution of biogenic secondary organic aerosol (SOA) loadings over the past millennium, and its contribution to the Earth's radiative balance. Furthermore, we will study the implications of human activities (through e.g. emission reduction policies and land-use change). The outcomes of the project will improve understanding of natural vs. human-induced changes in climate patterns, through new knowledge on e.g. the effects of changing vegetation patterns through deforestation and expansion of agriculture as compared with the changes in temperature and CO2 levels. The goal can be divided into three specific objectives: 1. To investigate the magnitude, variability, mixture and controlling factors of biogenic SOA and its impacts on climate during the past millennium. 2. To estimate the climate impacts of SOA as compared and in interaction with other natural and anthropogenic factors, and provide recommendations for the treatment of SOA in models. 3. To study the implications of different air quality and climate policy options (through e.g. emission reductions) for the atmospheric composition and climate. The research will be conducted through simulations primarily with the NorESM earth system model. The applied computational resources will be primarily used for these simulations If needed and space allows, the ESM simulations will be complemented with targeted simulations with smaller scale models.