http://www.metoffice.gov.uk/hadobs/crutem4/data/download.html http://www.cru.uea.ac.uk/cru/data/temperature/crutem4/station-data.htm
http://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/tree-ring
http://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/climate-reconstruction