Measurements of tree-ring widths are the most widely-distributed and best replicated source of surrogate environmental information on the planet, and are one of the main archives used to estimate changes in regional and global climate during the past several centuries or millennia. Because the Northern Hemisphere ring-width network is now so large, it is more crucial than ever to ensure our understanding of tree-environment relations is not influenced by decisions to include or exclude certain records. It may be the case that a particular set of ring-width records are, for whatever reason, more tightly coupled to a particular climate factor than other records from the same region or species and, as a result, may be superior estimators of that factor’s past behavior. At the same time, it is known that selecting a small number of predictors from a large pool of potential candidates increases the likelihood of a Type I error. That effect may be particularly relevant to dendroclimatology because the total number of available ring-width records is often much larger than the number of records used to produce reconstructions of large-scale climate features. As an initial step, it would be helpful if paleoclimate reconstructions derived from tree rings described more explicitly the criteria used to select ring-width records as potential predictors and specified those records excluded by that screening. By comparing ring-width chronologies and their relations with climate against the standard set by thousands of records across the hemisphere, we should be better able to distinguish climate signals from proxy noise and produce more accurate reconstructions of climate during the late Holocene.

1. GUARDING AGAINST
FALSE DISCOVERY
IN LARGE-SCALE
DENDRO
CHRONOLOGY
Sco! St. George
University of Minnesota
Understanding Uncertainties in Paleoclimate and Paleoecology: Age Models, Proxy Processes, and Beyond | December 18, 2014

2. 3ASSERTIONS
BASED ON
TREE-RING DATA

3. COSMIC
RAYS

4. “ … THERE WAS A CONSISTANT
”
AND SIGNIFICANT RELATIONSHIP
BETWEEN
GROWTH OF THE TREES
AND THE FLUX DENSITY OF
GALACTIC COSMIC RADIATION.
Dengel et al., 2009
New Phytologist

5. SOLAR
CYCLE

6. “ SPECTRAL ANALYSIS ALSO SHOW
”
THAT SIGNIFICANT PERIODICITIES
OF ~11 YEAR, 54 YEAR, AND 204 YEAR PEAKS
[IN TREE-RING DENSITY RECORDS]
RESPOND TO
THE SCHWABE CYCLE,
THE FOURTH HARMONIC OF THE SUESS CYCLE,
AND THE SUESS CYCLE,
RESPECTIVELY.
Duan and Zhang, 2014
Journal of Geophysical Research - Atmospheres

7. ATLANTIC
MULTIDECADAL
OSCILLATION

8. “ TUPELO HONEY YIELD-PER-HIVE
”
[RECONSTRUCTED FROM TREE-RING WIDTHS]
HAS OSCILLATED BETWEEN
MULTIDECADAL-LENGTH PERIODS OF LOW AND HIGH YIELDS
DURING THE PAST 211 YEARS
AND IS ASSOCIATED WITH
THE ATLANTIC MULTIDECADAL OSCILLATION.
Maxwell et al., 2013
Agricultural and Forest Meteorology

9. LARGE-SCALE
GEOPHYSICAL
PHENOMENA
SMALL SETS
OF TREE-RING WIDTH
DATA

10. BOTTOM-UP
APPROACH

11. JUNE TEMPERATURE
JULY TEMPERATURE
AUGUST TEMPERATURE
SEPTEMBER TEMPERATURE
OCTOBER TEMPERATURE
NOVEMBER TEMPERATURE
DECEMBER TEMPERATURE
JANUARY TEMPERATURE
FEBRUARY TEMPERATURE
MARCH TEMPERATURE
APRIL TEMPERATURE
MAY TEMPERATURE
JUNE TEMPERATURE
JULY TEMPERATURE
AUGUST TEMPERATURE
SEPTEMBER TEMPERATURE

12. p > 0.05

13. TYPE 1
ERROR

14. There are more than 3,200 publicly-available tree-ring records
Pinus
Picea
Quercus
Pseudotsuga
Larix
Nothofagus
Austrocedris
Phyllocladus
Agathis
Source: St. George, PAGES News, 2014
(and many more held by individual investigators).

15. FALSE
DISCOVERY
RATE

16. “ … THE EXPECTED PROPORTION
”
OF REJECTED LOCAL NULL HYPOTHESIS
THAT ARE
ACTUALLY TRUE.
Wilks, 2006
Journal of Applied Meteorology and Climatology

17. SYNOPTIC
APPROACH

19. Pinus
Picea
Pseudotsuga
Quercus
Larix
A
This map illustrates the reasonably-large subset
of the North American tree-ring width network
C
36ºN
18ºN
records
records
B
54ºN
72ºN
90ºN
180ºW 120ºW 60ºW 0º 60ºE 120ºE 180ºW
2000
1000
12%
6%
0º
Source: St. George et al., Geophysical Research Le!ers, 2013
analyzed by this study.

20. STRONG
WIDESPREAD
DIRECT

21. -0.8 -0.6 -0.4 -0.2 +0.2 +0.4 +0.6 +0.8
correlation coefficient
(ring-width vs. climate)

23. (a) Winter precipitation
WINTER PRECIPITATION
Source: St. George, Quaternary Science Reviews, 2014

25. Fri!s, H.C. Growth-rings of trees: their correlation with climate. Science 154, 973-975 (1966).

26. EL NIÑO SOUTHERN OSCILLATION

27. ENSO
Source: St. George, Quaternary Science Reviews, 2014

28. WEAK(ER)
UNCOMMON
INDIRECT

29. ATLANTIC
MULTIDECADAL
OSCILLATION

30. Source: St. George, Quaternary Science Reviews, 2014
ATLANTIC MULTIDECADAL
OSCILLATION

31. PACIFIC/
NORTH AMERICAN
PATTERN

32. (d) Pacific/North-American PACIFIC/NORTH AMERICAN
PATTERN
Source: St. George, Quaternary Science Reviews, 2014

33. ENSO PNA
475/2270
139/2270
records
records

34. p > 0.05

35. TYPE 1
ERROR

36. 3 POTENTIALLY-USEFUL
APPROACHES
TO ADDRESS
THIS CHALLENGE

37. STA1TISTICAL
SIMULATIONS

38. Dr. Dave Meko University of Arizona

40. EXACT
SIMULATION

41. +200
0
precipitation anomaly (mm)
-200
decadal target
decadal ‘noise’
1900 1920 1940 1960 1980 2000
Source: St. George and Ault, Journal of Geophysical Research - Atmospheres, 2011

42. FO2RWARD
MODELLING

43. Dr. Eugene Vaganov Siberian Federal University

44. Source: Vaganov et al., In Dendroclimatology, 2010

45. Synthetic tree-ring records generated by a forward model (and modern climate data)
Can we predict how local trees should respond to weak or remote climate influences?
oW
120exhibit largely the same spatial pa!erns in climate response as real trees.
60oW
0o 60oE
120oE
75oN
90oN
SOIL MOISTURE : TEMPERATURE
Source: Xiaolu (Grace) Li, Cornell University

46. SE3LECTION
CRITERIA

47. Pinus
Picea
Quercus
Pseudotsuga
Larix
Nothofagus
Austrocedris
Phyllocladus
Agathis
Source: St. George, PAGES News, 2014
Because the global ring-width network is now so large,
it is crucial to ensure our understanding of tree-environment relations is not influenced
by decisions to include or exclude particular records.