Ecological impacts of the recent warming trend in the Arctic are already noted as a decrease in tundra area with replacement by shrubs, and changes in the tree line. The potential impact of vegetation changes to feedbacks on the atmospheric climate system is enormous because of the large land surface impacted and the multiyear memory of the vegetation cover. While much of the vegetation information is anecdotical, and satellite NDVI (Normalized Difference Vegetation Index) estimates began in 1981, the Köppen climate classification can be used to relate surface types to monthly mean air temperature from the NCEP/NCAR reanalysis and from the Climate Research Unit, University of East Anglia, and thus serves as proxy data for earlier period. In Köppen classification, tundra area is defined as the warmest monthly mean temperature being less than 10°C and above freezing. We found a decrease in tundra area from the late 1970s to the present, similar to the increasing trend of the NDVI data. The decreases are largest in NW Canada, and eastern and coastal Siberia. Köppen proxies show an increase in tundra area from the late 1950s to the 1970s. A decreasing trend of tundra area was also identified at the beginning of the 20th century, with smooth slope.