Ground surface temperature histories inverted from subsurface temperatures of two boreholes located in Panxi, SW China

Variation of the ground surface temperature in the past is recorded in the sursurface temperature field. We reconstruct the ground surface temperature history by analysis of temperature-depth (T−z) profiles from two deep boreholes some 200 km apart in Panxi, southwest China. Consistent results have been derived using a variety of analysis methods: individual inversion of each T−z log, simultaneous inversion of the derived transient components of the two T−z logs, inversion of the average of the transients, and inversion of the residual T−z data after the steady state has been removed. Results show that a warming of about 1°C from 1600 to 1900 AD is evident in the borehole temperatures. The results also indicate that such a warming is at least in part a recovery of the climate from a preceding cold episode. The reconstructed ground surface temperature histories are in good agreement with the variation of the surface air temperature recorded in the Shanghai meteorological observatory for the period of their overlap.