In their study of tree rings from the Chemnitz Fossil Forest (Germany), Luthardt and Rößler (2017) claim to identify a regular near-11-yr cyclicity in growth, and present that pattern as evidence of the influence of the Schwabe solar cycle (Usokin and Mursula, 2003) on climate and forest productivity during the early Permian. If correctly interpreted, these fossil tree rings would indicate the sunspot cycle was the dominant influence on interannual variability in Earth’s climate during this period and that it has been a consistent aspect of our Sun’s behavior for at least the past 300 m.y. We argue the fossil tree-ring record from Chemnitz does not constitute reliable evidence of solar activity during the Permian because the individual tree-ring sequences are not correctly aligned (dendrochronologically dated) and, as a result, the mean ring-width composite is not a meaningful estimate of year-to-year variations in tree growth in this ancient forest.

1. WEIGHING THE EVIDENCE FOR SUNSPOT CYCLES IN FOSSIL TREES
Paleoclimate Seminar | Johannes Gutenberg-Universität Mainz | November 15, 2017

2. 1613CE

3. GALILEO GALILEI
Portrait by Justus Sustermans

4. JUNE 23, 1613
Source: The Galileo Project/M. Kornmesser

5. LETTERS ON SUNSPOTS (1613)

7. 1843CE

8. SAMUEL SCHWABE

9. 11-YR
SOLAR CYCLE

10. WE NOW HAVE A 400-YR LONG RECORD OF SUNSPOT NUMBERS, WHICH CLEARLY
SHOWS A NEAR-PERIODIC 11-YR CYCLE (AS WELL AS OTHER CHANGES).
Source: Robert Rohde

11. Source: Greg Kopp, University of Colorado
1880 1900 1920 1940 1960 1980 2000 2020
1360.2
1360.4
1360.6
1360.8
1361
1361.2
1361.4
1361.6
1361.8
W/m2
TOTAL SOLAR IRRADIENCE VARIES IN PHASE WITH THE SCHWABE CYCLE
WITH AN AMPLITUDE OF ABOUT 0.1% AROUND A MEAN VALUE OF 1361.5 W/M2.

12. ?WAS THE 11-YR SCHWABE CYCLE
A REGULAR COMPONENT
OF OUR SUN’S BEHAVIOR
PRIOR TO CE 1600?

14. A.E. DOUGLASS
Source: University of Arizona

16. PRACTICALLY ALL
THE GROUPS OF TREES INVESTIGATED
SHOW THE SUNSPOT CYCLE OR ITS MULTIPLES —
THE SOLAR CYCLE BECOMES
MORE CERTAIN AND ACCURATE
AS THE AREA… INCREASES
OR THE TIME OF A TREE RECORD
EXTENDS FARTHER BACK…
“ ”
A.E. Douglass
Climatic Cycles and Tree Growth, 1919

17. 1978CE

19. … LITTLE CONVINCING EVIDENCE
HAS YET BEEN PRODUCED
FOR REAL CORRELATIONS
BETWEEN SUNSPOT CYCLES
AND THE WEATHER/CLIMATE ON
THE 11- AND 22-YEAR TIIMESCALES.
“ ”
A.B. Pi ock
Reviews of Physics and Space Physics, 1978

20. DATA SELECTION
AUTOCORRELATION
SMOOTHING
POST HOC HYPOTHESI

21. HAD [DOUGLASS] BUT KNOWN IT,
THE SUNSPOT RECORD IS PROBABLY
BETTER PRESERVED
IN THE ISOTOPIC CHEMISTRY
OF THE RINGS
THAN IN THE RING-WIDTH SIGNAL!
“ ”
Brian Luckman
Tree Rings, Environment and Humanity, 1996

22. 14C

23. RADIOCARBON MEASUREMENTS (MADE ON TREE-RING-DATED WOOD SAMPLES)
HAVE BEEN USED TO RECONSTRUCT SUNSPOT NUMBERS DURING THE HOLOCENE.
Source: Solanki et al., Nature, 2004

24. Pinus
Picea
Quercus
Pseudotsuga
Larix
Nothofagus
Austrocedris
Phyllocladus
Agathis
Source: St. George, Past Global Changes Magazine, 2014

28. CHEMNITZ FOSSIL FOREST

29. LATE PERMIAN (260 MA)
Source: Dr. Ron Blakey, Northern Arizona University

30. CHEMNITZ FOSSIL FOREST

32. Source: Luthardt and Rößler, Geology, 2017

33. Source: Luthardt and Rößler, Geology, 2017

34. 43FOSSIL
TREES

35. Source: Luthardt and Rößler, Geology, 2017
AFTER ALIGNING TREE-RING WIDTH SEQUENCES FROM 11 TREES, LUTHARDT AND
RÖßLER CLAIMED TO IDENTIFY A REGULAR NEAR-11-YR CYCLICITY IN GROWTH.

36. LIKE TODAY
SUNSPOT ACTIVITY CAUSED
FLUCTUATIONS OF COSMIC RADIATION INPUT
TO THE ATMOSPHERE,
AFFECTING CLOUD FORMATION
AND ANNUAL RATES OF PRECIPITATION,
WHICH ARE REFLECTED IN THE TREE-RING ARCHIVE.
“ ”
Luthardt and Rößler
Geology, 2017

37. 11-YR CYCLE
300MILLION YEARS

40. THEY WERE
STUNNED
BY HOW CLEARLY
THEY COULD SEE
THE [SUNSPOT] CYCLES.
“ ”
The Economist
January 21, 2017

41. ICH AUCH
🤔

42. WEIRD
ERRORS

43. DOCUMENTATION OF SUNSPOT ACTIVITY
FOR THE PAST 1 M.Y.
BY 10BE AND 13C ISOTOPES
IN ICE CORES AND TREE RINGS
SUGGEST AN AVERAGE PERIODICITY
OF 11.12 YR (USOSKIN ET AL., 2015).
“ ”
Luthardt and Rößler
Geology, 2017

44. SHORT
SERIES

45. DATING HOLOCENE TREES

46. STRONG
CYCLES

47. Gleissberg (88-yrs) and de Vries (205-yrs) cycles
do not occur consistently through the Holocene
reconstruction4 of total solar irradiance (TSI) (Fig 3).
Figure 3. Spectra of the TSI reconstruction for
different time windows in the Holocene. Red points
mark frequencies with significant spectral power
(p=0.1).
Figure 6. Blue lines - proportion of records that have
significant power (p=0.1) at each frequency. Red
dashed line - the expected proportion. Frequencies
highlighted with a red point are significantly (p=0.1)
above this background. Number of records is shown
by the lower red line. Orange bands - frequencies
that have significant power in TSI reconstruction.
Dashed pale blue lines - 88 and 205 year-1 cycles.
• No window has more records with Gleissberg (88-
yrs) or de Vries (205-yrs) cycles than expected.
• There are not significantly more 88 or 205 year
cycles in time windows with these periods in TSI
Figure 2. Distribution of tree-ring width records
analysed. Records in red have significant spectral
power near the Schwabe cycle.
We hypothesise that if solar variability is an
important determinant of climate, these cycles will
occur more frequently in proxy records during time
windows with the cycles in TSI.
We test this with a compilation (Fig 4) of high-
resolution Holocene proxy-climate records collated
from various sources.
Figure 4. Proxy data used in at least one time
window. No tree-ring records were used.
For each time window, we
• Select proxy records that met standards for
resolution and coverage
• Identify significant frequencies (Fig 5).
• Report the percent of records that have significant
power at each frequency (Fig6).
Figure 5. Red points - frequencies that have
significant (p=0.1) spectral power in the time window
0-2000 BP. Orange bands - frequencies that have
significant power in TSI.
Is there robust evidence of solar variability in palaeoclimate proxy data?
Richard J. Telford, Kira Rehfeld & Scott St. George
Richard.Telford@uib.no Department of Biology, University of Bergen &
Bjerknes Centre for Climate Research, Norway @richardjtelford
kira.rehfeld@awi.de Alfred Wegner Institute, Potsdam, Germany
stgeorge@umn.edu University of Minnesota @ scottstgeorge
1. Schurer et at (2014 Nat. Geosci. 7: 104–108
2. See examples at https://quantpalaeo.wordpress.com/category/solar-variability/
3. St George (2014) Quat. Sci. Res. 95, 132-150
4. Steinhilber et al (2012) PNAS 109:5967-5971
The strength of the relationship between
variations in solar activity and climate is
contentious. Some authors find that solar
variability has relatively little effect1, but numerous
papers report evidence of the impact of solar
variability on palaeo-proxy climate data. This
suggests that solar variability is an important
determinant of climate variability. This evidence
needs to be treated with caution because of
1. methodological problems in many papers2
• eyeball-correlations of proxies
• multiple testing
• chronological adjustments to maximise
correlations
• confounding of solar variability by volcanic
forcing during last millennium
2. publication bias
• few papers reporting non-significant results are
published
To avoid these problems we undertake a systematic
review of high-resolution proxy data to detect solar
cycles.
Figure 1. a) Spectral
power of annual
sunspot numbers .
90% significance level
assumes the multi-
taper spectrum is
locally white.
b) spectral power of
the Herring Alpine
(Alaska) tree-ring
widths record.
c) percentage of the
ring-width records
that are significant at
p=0.1 by frequency.
We test for the 11-year Schwabe cycle in a
sample of tree-ring data3 from the World Data
Centre for Paleoclimatology.
• Interval AD 1750 - 1950
• 752 tree-ring width records met criteria for signal
quality and sample depth
• Annual sunspot counts show a clear spectral peak
centred at 11 years (Fig. 1a).
Some tree-ring width records have significant power
at 11 years-1 (Fig. 1b), but fewer than 10% of the
records exhibit significant power at p=0.1 (Fig. 1c),
and these are scattered geographically (Fig 2).
We conclude that we do not find robust evidence
of Schwabe (11-yrs), Gleissberg (88-yrs) or de Vries
(205-yrs) cycles in palaeoclimate data.
We are working to increase the number of proxy
records included in this analysis and perform
additional tests.
PDF available at
https://quantpalaeo.wordpress.com/?p=1242
This work was supported by the Norwegian Research Council
project PalaeoDrivers

50. ?
WERE THE CHEMNITZ TREE-RING SERIES
CORRECTLY-ALIGNED
(DENDROCHRONOLOGICALLY DATED)
AND IS THEIR MEAN RING-WIDTH CURVE
A MEANINGFUL ESTIMATE
OF TREE GROWTH
IN THIS ANCIENT FOREST?

51. CONCURRENT WIDE OR NARROW RINGS ARE THE MOST RELIABLE
CHRONOLOGICAL MARKERS IN PROPERLY DATED TREE-RING SEQUENCES .

52. WHAT A COLOR PLOT OF 100 YEARS OR SO
OF A DATED TREE-RING SEQUENCE LOOKS LIKE.

57. ?
WERE THE CHEMNITZ TREE-RING SERIES
CORRECTLY-ALIGNED
(DENDROCHRONOLOGICALLY DATED)
AND IS THEIR MEAN RING-WIDTH CURVE
A MEANINGFUL ESTIMATE
OF TREE GROWTH
IN THIS ANCIENT FOREST?

58. RING NUMBER
10 20 30 40 50 60 70 80
AVERAGE
growth
HIGH
growth
LOW
growth
COLOR PLOT ILLUSTRATING THE ALIGNMENT OF THE CHEMNITZ FOSSIL
TREE-RING SEQUENCES SUGGESTED BY LUTHARDT AND RÖßLER (2017).
Source: St. George and Telford, Geology, 2017

60. 50 60 70 80Source: St. George and Telford, Geology, 2017

61. 11TREE-RING SERIES
43FOSSIL TREES

63. -4
-2
0
2
4
1 10 20 30 40 50 60 70 80
Computed mean ring-width
Mean ring-width reported by L+R17
Ring number
THE MEAN RING-WIDTH COMPOSITE REPORTED IN THEIR ARTICLE
DOESN’T MATCH THE AVERAGE OF THEIR 11 TREE-RING SERIES.

64. DATA SELECTION
AUTOCORRELATION
SMOOTHING
POST HOC HYPOTHESI

65. SEQUENCES OF
THE RESULTING RING INDICES
WERE SMOOTHED
USING A THREE-POINT
MOVING AVERAGE SMOOTHER.
“ ”
Luthardt and Rößler
Geology, 2017

67. WHITE
NOISE

71. WE WANT TO
UNDERLINE THE DIFFICULTY
IN DIRECTLY COMPARING
ANY MODERN TREES, FORESTS, AND THEIR SITUTATION
WITH THAT OF EXTINCT PLANTS,
THEIR PALEOGEOGRAPHIC, PALEOCLIMATIC,
ENVIRONMENTAL, AND TAPHONOMIC RESPONSE.
“ ”
Luthardt and Rößler
Geology, 2017

72. Source: Luthardt and Rößler, Geology, 2017
“THEY WERE STUNNED BY HOW CLEARLY THEY COULD SEE
THE [SUNSPOT] CYCLES.”

73. WHITE
NOISE

74. … SIX OF ELEVEN SEQUENCES
SHOW A DISTINCT POWER PEAK
AT A PERIODICITY OF 9-12 YR, WHEREAS
TWO SEQUENCES (K349 AND K6044)
ARE STATISTICALLY ROBUST
(P < 0.05).
“ ”
Luthardt and Rößler
Geology, 2017

75. 2TREE-RING SERIES
43FOSSIL TREES

77. … TREE-RING SEQUENCES
REFLECT A SENSITIVE
FEEDBACK REACTION
OF EARLY PERMIAN MONSOONAL PALEOCLIMATE
TO VARIATIONS OF SOLAR IRRADIANCE.
“ ”
Luthardt and Rößler
Geology, 2017

78. SOLAR IRRADIANCE
WEATHER/CLIMATE
TERRESTRIAL ORGANISMS

81. “ZOMBIE”
THEORIES

85. @sco stgeorge