A Test of Borehole Paleoclimatology as a Method to Quantify Radiative Climate Forcing

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This award will test coherence between ground surface temperatures (GST) reconstructed from borehole temperature - depth (T-z) profiles, surface air temperatures (SAT), soil temperatures, and solar radiation. It will address the critical challenge of separation of forcing by anthropogenic greenhouse gases from natural radiative forcing. This challenge is difficult because the composite temperature signal in the meteorological and multi-proxy temperature records cannot be directly resolved into radiative forcing components. However, since radiative heating and heat exchange between the ground and the air directly control the ground surface temperature, a time-series of borehole T-z measurements spanning time periods when solar radiation, soil, and air temperatures have been recorded will enable comparison of the thermal energy stored in the ground to these quantities. If coherence between energy storage, solar radiation, GST, SAT and multi-proxy temperature data can be discerned for a one or two decade scale, synthesis of these data over the past several centuries may enable us to separately determine the anthropogenic and natural forcing of climate change. The data required for this project include: (1) New T-z measurements in boreholes previously used in paleoclimate and heat flow research in Canada and the United States from the 1970's to the present, (2) Meteorological data from the US Historical Climatology Network, the Automated Weather Data Network of the High Plains Regional Climate Center, and Environment Canada, and (3) Direct and remotely sensed data on surface land cover conditions at selected borehole and meteorological sites for the periods between borehole observations. The project addresses several related questions: What is the coherence between the GST, SAT, soil temperatures and solar radiation? Have microclimate changes at borehole sites and climate stations affected temperature trends? If good coherence is obtained, can the coherence between thermal energy stored in the ground and radiative forcing during the time between T-z measurements be extended several centuries into the past? Finally, this award will help assess the magnitude of climate change in North America from middle latitudes to polar regions to determine if the trends observed support the predictions of general circulation models.This research is in a new and emerging field with broad application and significant potential scientific payoff in integrating modern day and paleo-climate research. The data required for this project include: (1) New T-z measurements in boreholes previously used in paleoclimate and heat flow research in Canada and the United States from the 1970's to the present, (2) Meteorological data from the US Historical Climatology Network, the Automated Weather Data Network of the High Plains Regional Climate Center, and Environment Canada, and (3) Direct and remotely sensed data on surface land cover conditions at selected borehole and meteorological sites for the periods between borehole observations.The project addresses four related questions: What is the coherence between the GST, SAT, soil temperatures and solar radiation? Have microclimate changes at borehole sites and climate stations affected temperature trends? If good coherence is obtained, can the coherence between thermal energy stored in the ground and radiative forcing during the time between T-z measurements be extended several centuries into the past? Finally, this award will assess the magnitude of climate change in North America from middle latitudes to polar regions to determine if the trends observed support the predictions of general circulation models.This research is in a new and emerging field with broad application and significant potential scientific payoff in integrating modern day and paleo-climate research.