File list:
  20th-century-avg.tif - Global mean heat index, 1979-1999
  20th-century-max.tif - Global maximum heat index, 1979-1999
  20th-century-min.tif - Global minimum heat index, 1979-1999
  21st-century-avg.tif - Global mean heat index, 2000-2013
  21st-century-max.tif - Global maximum heat index, 2000-2013
  21st-century-min.tif - Global minimum heat index, 2000-2013
  country-clusters.csv - Heat index clusters by country & reference period
  country-means-century-20.csv - Monthly heat index values by country, 1979-1999
  country-means-century-21.csv - Monthly heat index values by country, 2000-2013
