Big questions for air/energy?

Here are some big questions that Peter outlined. The sub-group cannot do all of these, so we'll have to pick a few that are the most important. Which ones make a compelling paper that synthesizes data in a new and interesting way? Please comment...

1. What is the global contribution of GHG emissions by urban areas?
   
1. What is the global level of carbon equivalent emissions produced in urban areas and what is the urban share of total anthropogenic emissions?
2. What is the urban share by nation? 
3. What are the (end use) sectors responsible for these emissions, globally and nationally?
2. What is the global contribution of low-level emissions (e.g. CO, O3 VOC, NOX) by urban areas?
1. What is the level of these emission produced in urban areas and what is the urban share of total anthropogenic emissions?
2. What is the urban share by nation? 
3. What are the (end use) sectors responsible for these emissions, globally and nationally?
3. What are the air-regulatory services provided by cities?
1. What are the ecosystem offsets (trees, shrubs, soil)?
2. What are the social system offsets (management practices, wastewater, landfills, etc)
3. What mitigation and adaptation strategies that should we prioritize?
4. What is the future trend for cities and air regulatory services? What are cities projected to contribute globally to both low-level and global emissions by 2025 (or some other date in the future)?
1. What are future trends; how large will the increase in production (and share) of emissions going to be?
2. What are the drivers of these trends?
3. What proportion of cities is projected to have “high” production of low-level, health-related emissions?
4. What are the trends in offsets and adaptation/mitigation strategies?
5. What are the caveats to these analyses and what have we learned about current data and knowledge gaps that prohibit accurate calculation of any of the above?