Flying Through the Clouds: How Are Aerosols Impacting Our Climate?

Numerous scientific studies have demonstrated the strong impact aerosols have on our climate system. Yet, as opposed to greenhouse gases, our overall understanding of their impacts is poor, limiting our ability to predict our future climate.  One large reason for this lack of understanding stems from the fact that aerosols are chemically complex and can both warm or cool climate, depending on their composition.  Certain aerosols, such as sea spray, are highly reflective and can scatter light and thus cool our climate, whereas other aerosols such as soot formed during combustion, absorb light and lead to warming.  The manner in which different chemical species distributed within individual particles ultimately determines their ability to warm/cool the planet either through light scattering and absorption.  Furthermore the composition of an aerosol determines whether it will effectively form clouds, which have large, and poorly characterized, effects on our climate system. Finally, aerosols sources and chemistry vary spatially on relatively rapid timescales making it challenging to accurately measure them on a global scale. For these reasons, the impact of aerosols on climate remains the single largest uncertainty in our understanding of climate changes.  

 This presentation will focus on recent lab and field study efforts aimed at deriving a better understanding of aerosol impacts on climate.  Results will be presented from recent aircraft studies using state-of-the-art instruments for making in-situ measurements of aerosols and cloud seeds, probing aerosol impacts on clouds and precipitation. Highlights of key new results will be given as well as the challenges and next steps that must be taken to properly address the overall complexity of real world aerosols. It is evident that neither lab nor field studies offers adequate solutions to this large scale problem, and efforts must be made to bridge the simplicity of lab studies with the complexity of the real world.  In an effort to move in this direction, this presentation will highlight our most recent efforts to transfer real world complexity in the form of an ocean-atmosphere wave tank to the lab in an effort to perform controlled studies on marine aerosol chemistry, heterogeneous reactions, and climate-relevant properties.  The newest findings and implications for future climate modeling projections will be summarized.