Broken Hockey Sticks, 1500 Year Cycles, and Ocean Cooling

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Broken Hockey Sticks, 1500 Year Cycles, and Ocean
Cooling

• Dr. Craig LoehleNCASI Principal Scientist552 S
  Washington St., Ste. 224Naperville, Illinois
  60540

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The Broken Hockey Stick

• Fundamental assumptions of tree ring
  reconstruction are untested
  
• In fact, they are violated
• Ms published online in Climatic Change,Sept. 08
• A Mathematical Analysis of the Divergence
  Problem in Dendroclimatology

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Climate Reconstruction(based largely on tree
ring data)
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How is it Done?

• Assume linear model ring vs. temperature
• Fit to temperature histories, 20th Century
• Inverse function for past temperature from ring
  width / density

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Signs of Trouble

• Widespread observations of divergence
• good fit up to 1960
• more warming than predicted by tree rings after
  1960
  
• Explanations are speculative
• Individual trees
• may not respond to temperature
• may grow worse when warmer
• (PPT limits)

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IF Linear Response, Perfect Fit
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IF Nonlinear Response, Get Truncation (inversion)
Peaks become troughs!
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IF Ramp Response (no PPT Limitation),Get
Truncation
Ramp results from species maximum growth rate
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Conclusions

• Linear growth response invalid
• Nonlinear growth explains divergence
• Consequence
• cant guarantee detection of temperatures warmer
  than calibration period
  
• Flattens out timeseries reduces mean, range, and
  maximum
  
• Cant evaluate MWP or how unusual recent decades
  are from linear reconstructions
  
• Cant use nonlinear model because gives nonunique
  inverse model

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The 1500-Year Climate Cycle

• Dansgaard-Oschger events in ice core data
• About 1500 years apart
• Cause solar or ocean oscillator (multi-state
  system)
  
• Did they continue?

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Greenland Data AnalysisUpdated GICC05 ice core
chronology
d18O
Years BP (Yr 0 2000 AD)
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Greenland Data AnalysisBest-fit model for 30,000
to 37,000 BP(R2 0.36, period 1486 yrs)
d18O (values centered for better estimation of
cycles)
Years BP (Yr 0 2000 AD)
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Greenland Data AnalysisBest-fit model for 40,000
to 46,000 BP(R2 0.30, period 1598 yrs)
d18O (values centered for better estimation of
cycles)
Years BP (Yr 0 2000 AD)
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Greenland Data AnalysisBest-fit model for the
Holocene to 8000 BP(R2 0.45, period 1434 yrs)
d18O (values centered for better estimation of
cycles)
Years BP (Yr 0 2000 AD)
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Best-fit Model 1681- and 1470-Year
CyclesCompared to Loehle Reconstruction (R2
0.68, 0.65 respectively)(confidence intervals
not shown)
1470-yr cycle
Anomaly (C)
1681-yr cycle
Years BP (Yr 0 2000 AD)
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Best-fit Model to Moberg Low-Frequency Data
(1152-yr cycle, R2 0.69)and Fit to 1470-yr
cycle (R2 0.54)(confidence intervals not shown)
1152-yr cycle
1470-yr cycle
Anomaly (C)
Years BP (Yr 0 2000 AD)
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Best-fit Model to North Iceland Sea Surface
Temperature(1552-yr cycle, R2 0.20)Data shown
after linear cooling trend removal
Anomaly (C)
Years BP (Yr 0 2000 AD)
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Oxygen Isotope Data from Central Alps, past 9000
yrsBest-fit models for 2004 AD to 3500 BP and
6500 BP to 8996 BP (1479-yr cycle, R2 0.27,
peak-to-trough amplitude 0.33C)
-delta O-18 ()
Years BP (Yr 0 2000 AD)
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Temperature inferred from Japanese
CedarBest-free-form-fit (1089-yr cycle, R2
0.28) Best-fit when forced with 1470-yr cycle
looks similar (R2 0.22)
1089-yr cycle
Anomaly (C)
1470-yr cycle
Years BP (Yr 0 2000 AD)
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Conclusions

• Mean period 1524 yr vs. 1470 yr hypothetical
  (3.7 off)
  
• Models, data strongly agree on timing of MWP,
  LIA
  
• Supports role for this cycle in recent warming

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Ocean TemperaturesRecent Trends

• ARGOS float data
• To 700 m depth
• 4.5 years data
• Global coverage

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Ocean heat content
Ocean Heat Content (x 1022 J)
Calendar Year
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Ocean heat content smoothed with a 1-2-1
filterand overlaid with a best-fit linear plus
sinusoidal (seasonal) model (R2 0.85)
Ocean Heat Content (x 1022 J)
Calendar Year
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Ocean heat content smoothed with a 1-2-1
filterand overlaid with linear trend portion of
best-fit model (slope -0.35 x 1022 J/yr)
Ocean Heat Content (x 1022 J)
Calendar Year
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Recent Temperature Downturn Evident in Hadley Data
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Conclusions

• Cooling trend over past 4.5 years matches
  satellite, surface data
  
• Rate of cooling similar to rate of warming before
  2003