Anomalous ground warming versus surface air warming in the Canadian Prairie provinces

Modelling results of precision temperature logs made to depths of up to several hundred meters in numerous wells in the Canadian Prairie provinces (mostly Alberta) show evidence of average warming at the ground surface (GST) of 2.1 K (standard deviation = 0.9 K) mostly in the second half of this century. The GST warming signal for which higher frequency noise is cut off by the earth, which acts as a low-pass filter, correlates with the surface air warming (SAT) measured at screen level. A spatial comparison is made between the SAT warming and the GST warming for the last four decades in this region. A GIS (Geographic Information System) area cross tabulation was performed through the intersection of the classes of the ground and surface warming maps with a resulting contingency coefficient C= 0.805. Identical grid samples extracted from the ground warming and surface warming maps were related statistically with a resulting correlation coefficient of r= 0.75. Differences in the magnitudes of the warming exist due to the limited number of compatible data sets, errors in ground warming and air warming reconstructions, and land surface changes affecting the energy balance and subsurface heat fluxes. The influence of these effects requires further study. It is unlikely that all of the sites for which GST warming has been proven to correlate with air warming would have identical topography, vegetation, and hydrogeological disturbances for an area as large as the one under study (about 720,000 km2 ). The warming effect in the study area, as preserved by the ground, is mainly climate related.