My current interests are mainly directed at the so-called secondary aerosol effect on climate: the possibility that cloud microphysics, hence the climate, may change as a result of disturbances to the CLOUD CONDENSATION NUCLEI.
 
I am working with R. Benner on developing new techniques for investigating the chemical nature of submicron aerosols, going down in size to several tens of nanometers. We are interested in the physiochemistry of aerosols as they relate to cloud nucleation
 
Q. Ji and I have developed a new instrument called the CCNR (Cloud Condensation Nuclei Remover).
This instrument allows one to measure the supersaturation spectrum of the atmospheric cloud condensation nuclei. We plan to use it during the upcoming Indian Ocean Elxperiment (INDOEX).
 
I devote time on science policy issues, especially those relating to global climate change issues that involve the secondary aerosol effect 
 
I maintain long standing interests in atmospheric radiation, especially in passive remote sensing methods such as multi spectral sun photometry and aureolometry and photometric measurements of twilight.
 
Arctic Contamination issues are of interest to me. We have recently set up a four station monitoring network in Alaska (Barrow, Eagle, Homer and Poker Flat Rocket Range) to collect high volume samples of aerosols for chemical analysis. I'm involved in the AMAP (Arctic Monitoring and Assessment Program) and working with J. Pacyna and others preparing a chapter on heavy metals for the AMAP assessment.