20th Century North American Snow Extent Trends: Climate Change or Natural Climate Variability?

• Main Authors: Allan Frei, Gavin Gong, David A. Robinson, Gwangyong Choi, Debjani Ghatak, Yan Ge
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Climate change; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.603.4829; http://www.easternsnow.org/proceedings/2006/frei_et_al.pdf

The purpose of this analysis is to test the null hypothesis that continental scale variations in North American snow cover extent (NA SCE) can be explained by atmospheric circulation alone, without need to invoke additional explanatory factors such as climate change. We test the null hypothesis by (1) presenting what is known about decadal scale variations in twentieth century continental scale NA SCE, and (2) examining historical variations in surface climate, tropospheric and stratospheric circulation, as well as corollary evidence from arctic sea ice variations, to determine whether the available evidence supports or refutes the null hypothesis. In this presentation, preliminary results are presented focusing on snow extent during spring (i.e., March). The full report is being prepared for submission for publication elsewhere. METHODS AND DATA In order to test the null hypothesis, we utilize data sets that extend back to, and beyond, the mid twentieth century. Variations in snow depth, surface temperature and precipitation rate, as well as upper tropospheric and mid stratospheric geopotential heights and wind speeds are examined using time series, composite, and correlation analyses. Time series analyses are used to identify climatic features in these fields that covary over interannual and decadal time scales. To evaluate