Testing the ‘Hockey Stick’

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Presentation transcript:

Testing the ‘Hockey Stick’ Mann, Bradley and Hughes McIntyre and McKitrick VS Laura Zaunbrecher EAS 4803 April 22, 2008

Overview Proxy Data Methods Mann ‘Hockey Stick’ updates (vs. MM) Data Calibration Principle Component Analysis Comparison to Mann ‘98 Results Temperature Reconstruction Mann ‘Hockey Stick’ updates (vs. MM) Conclusions

Proxy Data 14 used here- Original used 415 2 Ice Core d18O records from Quelccaya Ice Cap in Peru 2 Ice Accumulation Records – Peru Svalbard Ice Melt (summer air temp) Greenland Ice Core d18O N. Patagonia, Tasmania, Yakutia, NC,SC, GA precipitation (tree ring widths) N. Patagonia, – dendrodensity NA Tree line Data

Methods -Calibration Each Proxy series is calibrated to the instrumental NH temperature record from 1880 to 1980

Mann EOF’s 1 and 2 Calibration should capture at least these first 2 EOFS Increasing temp ENSO

Principle Component Analysis -Retain up to the 4th Principle Component -Ignore EOF Analysis -[u,s,v] =svd(A,’econ’) = A U • W • VT

Principle Components NOISE!! =U(:,1) HOCKEY STICK!!! =U(:,2)

Comparison to MBH98 MUCH Noiser (more variant) than the complete dataset Hockey Stick is captured in PC2 Other PC’s are just Noise – likely from using only 14 Proxies Versus the 415 used in MBH98

Temperature Reconstruction Mann et al., 1998 -’Hockey Stick Temperature Spike ~0.3°C -Smaller Amplitude than found by MBH -Large Interdecadal Oscillations -Lots of Noise!!!!

McIntyre and McKitrick argue… Mann’s NHtemp reconstruction gives too much weight to PC1 and bristlecone pine Corrcoef(MannNHtemp, MannPC1) = 0.8765 Coorcoef(MannNHtemp,Bristlecone) =0.5144

Uses different calibration intervals Psuedo-proxy study Uses different statiscital technique –RegEM STILL GET THE HOCKEY STICK!!!!

Conclusions Majority of Signal is Noise Do not capture ENSO in PC’s when using the 14 proxies in this study Skipped some important steps – Verification, Weights (proxies were weighted equally here) DO get the ‘Hockey Stick’ as the major form of temperature variation (after noise) Global Warming is REAL!

Questions?