Global Trends in Aerosol-Cloud Interactions, in the NASA GISS-E3 climate model

Over the past century, aerosols played an important role in counterbalancing some of the greenhouse gas (GHG)-caused global warming and thus preventing even higher surface temperatures to be reached by now. However, recent trends in aerosol concentrations show that in many formerly polluted regions aerosol emissions have already decreased back to pre-1950 levels, and the more recent major polluting countries, such as China, have reached a turning point in the last decade, leaving only India and parts of South East Asia on an increasing trend. Over the past 20 years, which were well observed by Earth observing systems, the relationship in effective radiative forcing between GHG and aerosols have dramatically changed due to increasing GHG and decreasing aerosol forcing effects. The overarching science questions are: How have aerosol forcings changed over the past decades? How well can those trends be evaluated in the new GISS-E3 model and be detected in satellite data? How much of the recently observed increase in global warming is attributed to weakening aerosol forcing effects?

We are using a brand new version of the NASA GISS climate model, that resolves now tightly coupled processes between the aerosol and cloud microphysical schemes. We are examining in detail aerosol effects on clouds, as well as separating out GHG effects on cloud changes. The satellite era, especially covered by the CERES project that now has produced two decades of observed data on the Earth’s Energy Imbalance (EEI) will be the basis of this analysis.

We will discuss trends in modeled aerosol forcings and responses, and how much they can explain trends in Earth Radiation, in comparison to other forcing agents.