Disappearing “alpine tundra” Köppen climatic type in the western United States
Article first published online: 27 SEP 2007
Copyright 2007 by the American Geophysical Union.
Geophysical Research Letters
Volume 34, Issue 18, September 2007
How to Cite
2007), Disappearing “alpine tundra” Köppen climatic type in the western United States, Geophys. Res. Lett., 34, L18707, doi:10.1029/2007GL031253., and (
- Issue published online: 27 SEP 2007
- Article first published online: 27 SEP 2007
- Manuscript Accepted: 27 AUG 2007
- Manuscript Received: 6 JUL 2007
- mountain climate change;
- western US;
- climate classification
 We examine changes in the areal extent of the Köppen “alpine tundra” climate classification type for the mountainous western United States following the work of Kottek et al. (2006). We find a significant decline in the area occupied by this climate category. In the early decades of the 20th century, the mean temperature of the warmest month in the areas of the western U.S. with nominal alpine tundra climates ranged largely between ∼8.5°C and 9.5°C. In the last 20 years (1987–2006), rising temperatures have caused a significant fraction of these areas to exceed the 10°C threshold for alpine tundra classification. The result has been a 73% reduction in coverage of this climatic type. The remaining classified alpine tundra in the last 20 years now averages between ∼9°C–10°C during the warmest month, so that continued warming past the classification threshold, would imply that areas where this climate type is found today in the West will no longer be present.