Spatial patterns of ground heat gain in the Northern Hemisphere

Variations in the Earth's surface energy balance are recorded in the subsurface as perturbations of the steady state thermal field. Here we invert 558 temperature-depth profiles in the Northern Hemisphere (NH), in order to estimate the energy balance history at the continental surface from heat flux anomalies in the subsurface. The heat gain is spatially variable and does not appear to have been persistent for the last 200 years at all locations, but overall continental areas have absorbed energy in the last 50 years. Results indicate a mean surface heat flux of 20.6 mWm(-2) over the last 200 years. The total heat absorbed by the ground is 4.8 x 10(21)J and 13.3 x 10(21)J for the last 50 and 200 years respectively. We suggest that our results may be useful for state-of-the-art General Circulation Model (GCM) validation and for land-surface coupling schemes.