For more information on topics discussed in Lesson 4, see these selected references:
Links
[1] http://cdiac.esd.ornl.gov/trends/emis/em_cont.htm
[2] http://www.epa.gov/globalwarming/emissions/index.html
[3] http://www.grida.no/climate/vital/intro.htm
[4] http://www.epa.gov/ozone/science/
[5] http://www.epa.gov/globalwarming/climate/index.html
[6] http://yosemite.epa.gov/oar/globalwarming.nsf/content/ActionsIndividual.html
[7] http://www.giss.nasa.gov/edu/gwdebate/
[8] http://www.epa.gov/air/acidrain/
[9] http://pubs.usgs.gov/gip/acidrain/contents.html
[10] http://www.epa.gov/air/visibility/
[11] http://www.epa.gov/air/urbanair/6poll.html
[12] http://www.epa.gov/air/urbanair/co/what1.html