Using Borehole Temperature Profiles to Reconstruct and Test

1
Using Borehole Temperature Profiles to
Reconstruct and Test Surface Temperature
Scenarios Over the Last Millennium David S.
Chapman1, Michael G. Davis1, and Robert N.
Harris2 1 Department of Geology and Geophysics,
University of Utah 2 College of Ocean and
Atmospheric Sciences, Oregon State University

• Reconstructing surface temperature histories
• Borehole temperatures
• A hybrid (SAT, borehole temperature) method
• Proxies and pre-proxy mean temperature (PPM)

2
Instrumental Record
Air - Ground Tracking

• Disadvantages
• Short records (post 1860)
• Non climatic biases
• Station moves
• Instrument changes

• Advantages
• Direct measure of temperature
• Good fidelity
• Good spatial coverage

3
Multiproxy Reconstructions

• Advantages
• Long records (millennia)
• Annual resolution

• Disadvantages
• Temperature calibration issues
• Seasonal sensitivity
• Poor low frequency resolution

4
Measuring Temperature in the Earth
5
The Geothermal Method
6
Evidence From Alaska
7
Northern Hemisphere
8
Borehole Temp. Reconstruction

• Advantages
• Long records (centuries)
• Annual sensitivity
• Direct measure of temperature

• Disadvantages
• Loss of temporal resolution
• with time
• Arbitrary offset with SAT

9
Borehole-SAT Hybrid Method
10
Hybrid Method

• Advantages
• Long records (centuries)
• Direct measure of temperature
• Directly tied and compared
• to SAT record

• Disadvantages
• Loss of temporal
• resolution with time

11
Convergence of Reconstructions
12
Borehole Test for Reconstructions
13
(No Transcript)
14
Borehole Temperatures and Climate Change

• 1. Ramp inversion of borehole temperatures yields
  1.2 C of warming from ca 1500 to year 2000.
• 2. The hybrid (SAT borehole T) model yields
  1.1 C of warming from ca 1750 to year 2000.
• Several proxy reconstructions are converging on 1
  C of warming.
• Cautions frequency sensitivity spatial
  coverage seasonality etc.
• Borehole temperatures provide tests for long term
  climate reconstructions.