GROUND SURFACE-TEMPERATURE HISTORIES INVERTED FROM SUBSURFACE TEMPERATURES OF 2 BOREHOLES LOCATED IN PANXI, SW CHINA

Variation of the ground surface temperature in the past is recorded in the subsurface temperature field. We reconstruct the ground surface t emperature history by analysis of temperature-depth (T-z) profiles fro m two deep boreholes some 200 km apart in Panxi, southwest China. Cons istent results have been derived using a variety of analysis methods: individual inversion of each T-z log, simultaneous inversion of the de rived transient components of the two T-z logs, inversion of the avera ge 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 degrees C from 1600 to 1900 AD is evident in the borehole temperature s. The results also indicate that such a warming is at least in part a recovery of the climate from a preceding cold episode. The reconstruc ted ground surface temperature histories are in good agreement with th e variation of the surface air temperature recorded in the Shanghai me teorological observatory for the period of their overlap.