Title: Surface Temperature Anomalies for the Medieval Warm Period, Little Ice Age, and 20th Century Warming Determined from Borehole Temperatures
1Surface Temperature Anomalies for the Medieval
Warm Period, Little Ice Age, and 20th Century
Warming Determined from Borehole Temperatures
- David S. Chapman, Robert N. Harris
- and Michael G. Davis
2I t
Concept surface temperature histories have
distinctive borehole temperature signatures.
Snapshot at t
3Medieval Climate Anomaly (MCA)
Background I
Mann et al. 2009, Global Signatures and
Dynamical Origins of the Little Ice Age and
Medieval Climate Anomaly, Science, 326, 1256
1260.
Little Ice Age (LIA)
4MCA LIA Temperature Difference in Proxy-based
Temperature Reconstruction
Background II 1. Temp differences
avoid zero problem 2. Mean difference
0.24 C 3. Local differences gt 1 C 4.
Variability
Mann et al. 2009, Science, 326.
5 Temperature Anomaly (C)
Amplitude (oC) LIA MCA -0.5 0.5
LIA MCA -0.5 0.0
LIA MCA -0.5 0.25
LIA MCA -0.25 0.5
LIA MCA 0.0 0.5
6Regions having multiple boreholes with depth gt
600m
7N 45
8N 12
9N 45
10N 5
Problems Small sample Suspicious profiles Lack
of thermal conductivity info.
11Chapman Davis Eos, Sept 14, 2010
12Conclusions
- Borehole T(z) useful complement to multiproxy
methods. - MCA, LIA, and recent warming have distinctive
signatures in borehole temperature profiles
(shape, amplitude, depth extent). - Four regions (NE N. America S. Africa Cent.
Europe Cent. Asia) do not have borehole T(z)
anomalies identifiable as MCA, LIA. - Amplitudes no greater than suggested by Mann et
al. - MCA/LIA stronger seasonal rather than annual
signal? - Borehole temperature noise level too great.
- Extensive warm period prior to 1000 CE
inconsistent with baseline temperature from
borehole studies - More deep (gt 600 m) boreholes with thermal
conductivity information needed. - If geog. variability real, less reliance on
stacking.