The cryosphere, or Earth’s frozen realm, is widely thought of as a wonderful monitor of climate change. The idea that warming reduces the area extent and/or persistence of frozen ground, snow cover, sea ice, and glaciers seems rather straightforward. Using the cryosphere as a natural barometer of global warming appears to be ideal considering the fact that the high latitude regions of the Northern Hemisphere are associated with some of the largest increase in surface air temperature both observed during the 20th century and predicted for the 21st century. Reduction of the cryosphere should be a train run amok, as frozen surfaces positively feed back to the overlying atmosphere such that without refrigeration from beneath, the overlying atmosphere should become even warmer.
Information about changes in the cryosphere has become widely available over the past two decades through satellite-derived data sets. However, in-situ observations of the cryosphere, or direct measurements from on the ground, are valuable because they can be used for validation of remote sensing products. But more importantly, in-situ observations provide a much longer record than satellite data sets, making them better monitors of the long-term climate. A newly assessed “state of the ground” data set for northern Eurasia has hit the streets, and the in-situ data offer an interesting caveat to the global warming debate.