The National Climatic Data Center has long served the Nation as a national resource for climate information. NCDC develops national and global data sets used by government and the private sector. NCDC's climate data has been used in agriculture, air quality, construction, education, energy, engineering, forestry, health, insurance, landscape design, livestock management, manufacturing, recreation and tourism, retailing, transportation, and water resources management. The center's data fulfills needs ranging from building codes to power plant and space shuttle design.
Here's NCDC's FAQ's on Global Warming
http://www.ncdc.noaa.gov/oa/climate/globalwarming.html
If you have questions about where you can find or obtain data, you can write to
ncdc.info@noaa.gov