AGU: Geophysical Research Letters

 

Editors' Highlight

Reconstructing past surface temperatures with borehole heat flux and temperature data

Reconstructing past climate provides a useful context for discussions of current and future climate changes. One way to assess past temperatures is by using temperature measurements in deep boreholes, which are narrow vertical shafts drilled several hundred meters into the ground. Because variations in the ground surface temperature over time affect the distribution of temperature in the subsurface, scientists can carefully measure the temperature at depth within these holes and then use mathematical formulas to infer past temperatures at the surface. By integrating a global database of terrestrial heat flux measurements with another database of temperature versus depth within boreholes and with the twentieth-century instrumental record of surface temperature, Huang et al. (2008) were able to reconstruct the surface temperature history over the past 20,000 years. The authors could clearly identify a long-term warming from the Last Glacial Maximum, a mid-Holocene warm episode, the Medieval Warm Period, the Little Ice Age, and the rapid warming of the twentieth century.

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