With the endorsement and support from the U.S. Environmental Protection Agency, European Commission, and Environment Canada, a project entitled Air Quality Model Evaluation International Initiative (AQMEII) was launched in 2009 by bringing together scientists from Europe and North America (Rao ST, Galmarini S, Puckett K, Bull Am Meteorol Soc 92:23–30, 2011). Several regional-scale numerical photochemical models were applied over the North American and European domains with 2006 emissions inventory. Several papers resulting from this international collaborative effort were accepted for publication in the AQMEII special issue of Atmospheric Environment. Also, a large 4-D database, assembled by EU Joint Research Centre for the AQMEII project, is now available to all scientists interested in developing innovative model evaluation techniques (Galmarini S, Rao ST, Atmos Environ 45(14):2464, 2011). Having successfully completed the first phase of AQMEII, Phase 2 of AQMEII was launched at the 2011 AQMEII workshop in Chapel Hill, NC, USA to focus on the interactions of air quality and climate change. In Phase 2, coupled meteorology-atmospheric chemistry models will be exercised over the two continents with a common emissions database to assess how well the current generation of coupled regional-scale air quality models can simulate the spatio-temporal variability in the optical and radiative characteristics of atmospheric aerosols and associated feedbacks among aerosols, radiations, clouds, and precipitation. The results from AQMEII Phase 2 would be useful to policy makers for developing effective policies to deal with air pollution and climate change.