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How long do trees remember?

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HOW LONG DO TREES REMEMBER?
Climate Variability Across Scales Working Group | PAGES (Past Global Changes) | August 13, 2020

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MUCH OF WHAT WE KNOW REGARDING VARIATIONS IN EARTH'S
CLIMATE DURING THE PAST MILLENNIUM COMES FROM TREE RINGS.
TREE RINGS,...

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MUCH OF WHAT WE KNOW
REGARDING VARIATIONS
IN EARTH'S CLIMATE
DURING THE PAST MILLENNIUM
COMES FROM TREE RINGS.

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How long do trees remember?

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Much of what we know regarding variations in Earth's climate during the past millennium comes from tree rings. But tree rings, like other proxies, attenuate some climate signals but amplify others, and their fidelity at longer timescales is difficult to gage. Even though dendroclimatology is well-established, questions remain about the climate clues encoded in tree rings — particularly at decadal-to-centennial timescales.

Much of what we know regarding variations in Earth's climate during the past millennium comes from tree rings. But tree rings, like other proxies, attenuate some climate signals but amplify others, and their fidelity at longer timescales is difficult to gage. Even though dendroclimatology is well-established, questions remain about the climate clues encoded in tree rings — particularly at decadal-to-centennial timescales.

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How long do trees remember?

  1. 1. HOW LONG DO TREES REMEMBER? Climate Variability Across Scales Working Group | PAGES (Past Global Changes) | August 13, 2020
  2. 2. MUCH OF WHAT WE KNOW REGARDING VARIATIONS IN EARTH'S CLIMATE DURING THE PAST MILLENNIUM COMES FROM TREE RINGS. TREE RINGS, LIKE OTHER PROXIES, ATTENUATE SOME CLIMATE SIGNALS BUT AMPLIFY OTHERS, AND THEIR FIDELITY AT LONGER TIMESCALES IS DIFFICULT TO GAGE. DENDROCLIMATOLOGY IS WELL-ESTABLISHED BUT QUESTIONS REMAIN ABOUT THE CLIMATE CLUES ENCODED IN TREE RINGS — PARTICULARLY AT DECADAL-TO-CENTENNIAL TIMESCALES.
  3. 3. MUCH OF WHAT WE KNOW REGARDING VARIATIONS IN EARTH'S CLIMATE DURING THE PAST MILLENNIUM COMES FROM TREE RINGS.
  4. 4. NEUKOM ET AL 2019 NO EVIDENCE FOR GLOBALLY COHERENT WARM AND COLD PERIODS OVER THE PRE-INDUSTRIAL COMMON ERA
  5. 5. Source: Emile-Geay et al., Scientific Data (2017) IN 2017, THE PAGES 2K INITIATIVE RELEASED A GLOBAL, COMMUNITY-SOURCED DATABASE OF TEMPERATURE-SENSITIVE PROXIES SPANNING THE PAST TWO MILLENNIA.
  6. 6. Source: Emile-Geay et al., Scientific Data (2017)
  7. 7. HURST 1956 THE PROBLEM OF LONG-TERM STORAGE IN RESERVOIRS
  8. 8. Source: Hurst, Hydrological Sciences Journal (1956) TREE-RING WIDTHS WERE AMONG THE INITIAL TYPES OF EVIDENCE USED BY HURST TO DESCRIBE LONG-RANGE PERSISTENCE IN HYDROLOGICAL AND GEOPHYSICAL TIME SERIES.
  9. 9. LOVEJOY SCHERTZER 2012 STOCHASTIC AND SCALING CLIMATE SENSITIVITIES: SOLAR, VOLCANIC AND ORBITAL FORCINGS
  10. 10. Source: Lovejoy and Schertzer, Geophysical Research Le ers (2012) BETWEEN 1 AND 500 YR, THEIR STOCHASTIC ESTIMATE OF CLIMATE SENSITIVITY LEANS HEAVILY ON RECONSTRUCTIONS DERIVED MAINLY FROM TREE RINGS.
  11. 11. INTERNATIONAL TREE-RING DATABANK4,949 TOTAL RING-WIDTH 621 LATEWOOD WIDTH 619 EARLYWOOD WIDTH 575 MAXIMUM LATEWOOD DENSITY 31 OXYGEN-18 26 BLUE INTENSITY 24 CARBON-13 Accessed August 6, 2020
  12. 12. TREES ARE NOT THERMOMETERS OR RAIN GAUGES. “ ” Keith Briffa and colleagues Climate Variations and Forcing Mechanisms of the Last 2000 Years, 1996
  13. 13. TREE RINGS, LIKE OTHER PROXIES, ATTENUATE SOME CLIMATE SIGNALS BUT AMPLIFY OTHERS, AND THEIR FIDELITY AT LONGER TIMESCALES IS DIFFICULT TO GAGE.
  14. 14. AGE/SIZE PERSISTENCE
  15. 15. Tree age Ring width AS TREES GROW LARGER WITH AGE, THEY ARE OBLIGED TO FORM NEW WOOD ABOUT THE EVER-INCREASING CIRCUMFERENCE OF THEIR BOLE.
  16. 16. Source: Björkland et al., New Phytologist (2017) MAXIMUM LATEWOOD DENSITY INCREASES AS TREES TRANSITION FROM JUVENILE TO MATURE WOOD, BUT LATER DECREASES AS FEWER RESOURCES ARE USED TO THICKEN CELL WALLS.
  17. 17. COOK ET AL 1995 THE ‘SEGMENT-LENGTH CURSE’ IN LONG TREE-RING CHRONOLOGY DEVELOPMENT FOR PALEOCLIMATIC STUDIES
  18. 18. TRADITIONAL TREE-RING STANDARDIZATION METHODS WOULD SEEM TO PLACE A FUNDAMENTAL LIMIT ON THE RESOLVABILITY OF VERY LOW-FREQUENCY CLIMATE FLUCTUATIONS FROM TREE RINGS WHEN CLIMATE CHANGES MORE SLOWLY THAN THE TYPICAL LIFESPAN OF THE TREES BEING STUDIED. “ ” Ed Cook et al., 1995 The Holocene
  19. 19. KLIPPEL ET AL 2020 DIFFERING PRE- INDUSTRIAL COOLING TRENDS BETWEEN TREE RINGS AND LOWER-RESOLUTION TEMPERATURE PROXIES
  20. 20. Source: Klippel et al., Climate of the Past (2020) COMPOSITES OF MARINE SEDIMENTS (ORANGE), LAKE SEDIMENTS (RED), AND GLACIAL ICE CORES (BLUE) HAVE STRONG PRE-INDUSTRIAL COOLING TRENDS. BUT TREE RINGS (GREEN) DON’T!
  21. 21. AGE/SIZE PERSISTENCE
  22. 22. COULTHARD ET AL 2020 THE LIMITS OF FREELY-AVAILABLE TREE-RING CHRONOLOGIES
  23. 23. Source: Coulthard et al., Quaternary Science Reviews (2020) TREE-RING SEQUENCES USUALLY EXHIBIT HIGH PERSISTENCE OVER SEVERAL YEARS DUE TO BIOLOGY (ARISING FROM CARBOHYDRATE STORAGE OR NEEDLE RETENTION) OR CLIMATE (DRIVEN BY LAGS IN TEMPERATURE OR HYDROLOGY).
  24. 24. REDSHIFT
  25. 25. TREE RINGS ARE NOT THE ONLY PROXY WITH THESE KINDS OF PROBLEMS…( )
  26. 26. HUYBERS ET AL 2015 RESPONSE OF CLOSED BASIN LAKES TO INTERANNUAL CLIMATE VARIABILITY
  27. 27. Source: Huybers et al.,Climate Dynamics (2015) EVEN IF THE CLIMATIC ‘INPUTS’ TO A CLOSED BASIN HAVE LITTLE OR NO PERSISTENCE, LAKE LEVELS WILL EXHIBIT STRONG LONG-TERM MEMORY DUE TO HYDROLOGICAL STORAGE.
  28. 28. IN PRINCIPLE, PROXY AND GCM DATA SHOULD YIELD A CONSISTENT VIEW OF THE CLIMATE SYSTEM ON [DECADAL AND LONGER] TIMESCALES. IN PRACTICE… “ ” Toby Ault CLIVAR Exchanges/Past Global Changes Magazine, 2017
  29. 29. Source: Chase et al., Elements (2018) THE ELDERFIELD CURVE OF HOW CONFIDENCE IN A GIVEN PROXY EVOLVES OVER TIME old-fashioned phase?
  30. 30. DENDROCLIMATOLOGY IS WELL- ESTABLISHED BUT QUESTIONS REMAIN ABOUT THE CLIMATE CLUES ENCODED IN TREE RINGS — PARTICULARLY AT DECADAL- TO-CENTENNIAL TIMESCALES.
  31. 31. FIRST LAW OF GEOGRAPHY
  32. 32. EVERYTHING IS RELATED TO EVERYTHING ELSE, BUT NEAR THINGS ARE MORE RELATED THAN DISTANT THINGS. “ ” Waldo Tobler University of California, Santa Barbara
  33. 33. Widespread drought caused narrow rings to form across the southwest USA during 1748 and 1750. Source: Kurt Kipfmueller, University of Minnesota
  34. 34. HOW DOES THE AGREEMENT BETWEEN TREE-RING RECORDS AT DECADAL FREQUENCIES AND LONGER VARY ACROSS SPACE AND TIME? and what is a reasonable expectation (null hypothesis) for that behavior?
  35. 35. SIGNAL- FREE” “
  36. 36. McPARTLAND ET AL TBD DOES SIGNAL-FREE DETRENDING INCREASE CHRONOLOGY COHERENCE IN LARGE TREE-RING NETWORKS?
  37. 37. Signal-free detrending can make tree-ring chronologies more coherent with their neighbors (➡), but in other cases, it appears to introduce low-frequency noise ( ). Source: McPartland et al., Dendrochronologia (revision submi ed) ➡ ➡
  38. 38. IS IT POSSIBLE TO IDENTIFY AN OPTIMAL DETRENDING FOR THE RECOVERY OF LOW-FREQUENCY PATTERNS FROM TREE-RING NETWORKS OF VARIOUS SIZES AND COMPOSITIONS? and is it a good idea to do that?
  39. 39. PROCESS MODELS
  40. 40. …ONE MAY MODEL THE FORMATION OF THE RECORD BY EXPLICITLY REPRESENTING THE CHAIN OF PHYSICAL AND BIOLOGICAL PROCESSES WHICH LIE BETWEEN THE CLIMATIC INFORMATION AND THE OBSERVED SIGNAL. “ ” Joël Guiot Past Global Changes Magazine, 2017
  41. 41. DEE ET AL 2017 IMPROVED SPECTRAL COMPARISONS OF PALEOCLIMATE MODELS AND OBSERVATIONS VIA PROXY SYSTEM MODELING: IMPLICATIONS FOR MULTI- DECADAL VARIABILITY
  42. 42. Source: Dee et al., Earth and Planetary Science Le ers (2017) THE SPECTRA OF SYNTHETIC TREE-RING WIDTHS GENERATED BY PROCESS MODELS (GREEN LINE, GRAY ERROR ESTIMATES) GENERALLY MATCH THE BEHAVIOR OF THE REAL DATA (BLACK LINE).
  43. 43. CAN WE USE PROCESS MODELS TO CONSTRAIN THE UPPER OR LOWER LIMITS OF DECADAL-TO-CENTENNIAL CLIMATE VARIABILITY DURING THE PAST TWO MILLENNIUM?
  44. 44. Source: Kevin Anchukaitis, University of Arizona
  45. 45. @sco stgeorge

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