1. A Multidisciplinary Analysis of Climate Change: Testing Borehole Paleoclimatology W. Gosnold, J. Majorowicz, S. Wood University of North Dakota Grand Forks, ND This research is supported by National Science Foundation Award ATM - 0318384

2. A critical challenge in global change research is separation of radiative forcing by anthropogenic greenhouse gases from radiative forcing due to natural climate variability.

3. Essential to meeting this challenge is determination of past climate changes using data from all possible sources, e.g., tree rings, ice cores, corals, boreholes, lake and ocean sediments, for example and then linking the paleoclimate record with the modern meteorological record.

4. Multiproxy, borehole, and meteorological records

5. We have initiated a multidisciplinary project involving five scientists in the US and two in Canada to test coherence between: ground surface temperatures (GST) reconstructed from borehole T-z profiles surface air temperatures (SAT) soil temperatures solar radiation Expertise applied in this project includes: heat flow, microclimatology, solar radiation, meteorology, and remote sensing.

6. The Research Team Will Gosnold UND Heat Flow and Team Leader Paul Todhunter UND Microclimate Jacek Majorowicz UND Heat Flow Xiquan Dong UND Solar Radiation Brad Rundquist UND Remote Sensing & GIS Dave Blackwell SMU Heat Flow Jean-Claude Mareschal QUAM Heat Flow Julie Popham UND Meteorology Shaun Wood UND Climate Modeling

7. Research plan Determine heat balance at selected borehole sites using the changes in temperature-depth measurements made during the past 20 years. Use AWDN radiation data to determine radiative component of heat balance. Synthesize the long-term temperature record from deep boreholes with the multi-proxy temperature record and the meteorological record.

8. Our Working Hypothesis Radiative heating and heat exchange between the ground and the air directly control the ground surface temperature, and 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.

12. Diurnal and seasonal disturbances of the geothermal gradient are approximately sinusoidal and the temperature at a depth x can be determined by T = A e -x√ω/2κ cos (ωt - -x√ω/2κ) Where T = A e -x√ω/2κ is the amplitude at depth x and -x√ω/2κ is the phase retardation of the maxima and minima of temperature at depth x. A is the amplitude at the surfae, ω is angular frequency, and κ is thermal diffusivity. Diurnal signals damp out in the upper meter and annual signals damp out within the upper 20 to 30 m.

13. The effect of a 2 degree shift in mean annual surface is shown for three different periods: Red curves: one year Green curves: ten years Blue curves: 100 years

14. The ground is an excellent filter for temperature signals. Short period (high frequency) signals are removed. Long period signals that may have been obscured in the “noise” are revealed.

16. Diffusion of Surface Temperature into the Subsurface

17. Synthetic T-z profiles at different times from GHCN for latitudes 60N- 90N

18. Tz profiles from 46N to 50N within longitude 96W to 104W

19. GSTH binned by latitude in the North American Great Plains supports predictions of CO2 models

21. Example of surface warming observed in 3 boreholes in North American Great Plains

25. Matching change in borehole Tz with AWDN stations

27. Monthly Air Temperatures Showing no Apparent Pattern or Trend

29. When projected into the subsurface the air temperature data reveal the 11 yr solar cycle

30. Air and Subsurface combined

31. Global Temperature Anomaly

32. Lean, J.. 2004. Solar Irradiance Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2004-035. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

33. Crowley, T.J., 2000, Causes of Climate Change Over the Past 1000 Years, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2000-045. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

36. Conclusions Repeat temperature ‑ depth (T ‑ z) measurements made at different times in a span of one or more decades in the same borehole can provide information that may lead to better understanding of the forcing mechanisms of climate change. Repeat temperature ‑ depth (T ‑ z) measurements made at different times in a span of one or more decades in the same borehole can provide information that may lead to better understanding of the forcing mechanisms of climate change.

37. Conclusion 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 anthropogenic and natural forcing of climate change. Our current research provides a comprehensive test of this hypothesis. 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 anthropogenic and natural forcing of climate change. Our current research provides a comprehensive test of this hypothesis. This research is supported by National Science Foundation Award ATM - 0318384