Pepin, N. and Losleben, M. 2002. Climate change in the Colorado Rocky Mountains: Free air versus surface temperature trends. International Journal of Climatology 22: 311-329.
What was done
The authors studied changes in surface and free-air temperatures over the period 1952-98 at three sites in Colorado, USA, ranging in elevation from 1509 meters to 3749 meters.
What was learned
In terms of surface air temperature, the authors discovered "absolute cooling at the highest elevations, but little temperature change on the high plains." In terms of air equivalent temperatures derived from radiosonde ascents from Denver and Grand Junction, however, they found "absolute warming at all levels."
What it means
In the words of the authors, the "rapid cooling in the alpine tundra that could not be predicted from the free-air record [casts] doubt upon the strong dependence on free-air temperature changes in climate modeling when investigating the potential effects of global warming in mountainous regions." What is predicted by climate models for the free air, in other words - and what is sometimes even observed in the free air - is not necessarily what is observed in the surface air temperature record. In fact, as discovered in this particular instance, just the opposite occurred, i.e., cooling instead of warming.
Reviewed 14 August 2002