geog5839.19, dendroclimatology
TRANSCRIPT
November 13
Dendroclimatology
Dr. Brian Luckman University of Western Ontario
Tree-ring-derived records have played a prominent role in a!empts to establish how climate has varied in the recent past.
“ ”Jones et al.
The Holocene, 2009
What characteristics of tree-ring records make them useful tools
to understand ancient climates?
CLIMATE FROM TREES
COMPLICATIONS AND CHALLENGES
TAKING THE PLANET’S TEMPERATURE
CLIMATE FROM TREES
2010 Jan-Aug temperature anomaly"h!p://www.giss.nasa.gov/
Source: St. George and Luckman, 2001
Ct = Rt - At - δD1t - δD2t - Et
THE PRINCIPLE OF AGGREGATE TREE GROWTH
THE PRINCIPLE OF
ECOLOGICAL AMPLITUDE
THE PRINCIPLE OF
SITE SELECTION
THE PRINCIPLE OF
AGGREGATE TREE GROWTH
THE PRINCIPLE OF
REPLICATION
STANDARDIZATION
THE PRINCIPLE OF
CROSS-DATING
How do we KNOW that tree rings are tracking a SPECIFIC climate?
Source: Minyoung Choi
Single-site reconstruction
Source: Hughes and Funkhouser, 1998
tree rings
rain gauges
correlation The Pearson product-moment correlation coe#cient is probably the single most widely used statistic for summarizing the relationship between two variables.
variable ‘X’
variable ‘Y’ r = +1.0
variable ‘X’
variable ‘Y’ r = -1.0
variable ‘X’
variable ‘Y’r = +0.85
Ring-width index
CORRELATIONFUNCTION
Source: St. George and Luckman, 2001
Ring-width index
Ring-width index
yt = axt + b + ε
yt = axt + b + ε
the climate variable of interest (at year t)
the tree-ring variable (at year t)
Source: Woodhouse et al., 2006
Tree rings can provide extra-ordinarily good estimates (sometimes)
TAKING THE PLANET’S TEMPERATURE
Temperature-sensitive trees"Northeastern Alaska
Source: Esper et al., Science, 2002
Long, temperature-sensitive tree-ring records have been used to estimate average temperatures across the entire hemisphere or globe.
Source: Esper et al., Science, 2002
Source: D’Arrigo et al., 2006
Source: D’Arrigo et al., 2006
Source: Osborne and Bri$a, 2006
Tree-rings also allow the reconstruction of large-scale regional or global temperature pa!erns defined by large networks of chronologies.
“ ”Brian Luckman
Geoscience Canada, 2010
Source: Bri$a et al., Global and Planetary Change, 2004
How do we KNOW that tree rings are any GOOD at “reverse predicting”
past climate?
1883“THE LOUDEST SOUND IN MODERN HISTORY”
Krakatau, Indonesia 1883
h!p://www.cru.uea.ac.uk/cru/people/bri$a/temmaps/
Mount Tambora, Indonesia Its eruption in 1815 was the most explosive since AD 180
1816THE “YEAR WITHOUT A SUMMER”
h!p://www.cru.uea.ac.uk/cru/people/bri$a/temmaps/
Huaynaputina Peru
h!p://www.cru.uea.ac.uk/cru/people/bri$a/temmaps/
Source: Bri$a et al., Global and Biological Change, 2004
Photograph: Mark Anbinder
Source: Intergovernmental Panel on Climate Change, 2007
COMPLICATIONS AND CHALLENGES
Tree rings are not thermometers or rain gages.“ ”Keith Bri$a and colleagues
Climate Variations and Forcing Mechanisms of the Last 2000 Years, 1996
THED I V E R G E N C E
PROBLEM
Source: D’Arrigo et al., 2008
the ‘divergence problem’ is defined as the tendency for tree growth at some previously temperature-limited northern sites to demonstrate a weakening in mean temperature response in recent decades.
Source: D’Arrigo et al., 2008
Source: D’Arrigo et al., 2008
It is important to stress that not all high-latitude regions display this apparent decoupling between observed and dendroclimatically estimated temperatures.
“ ”Phil Jones and colleagues
The Holocene, 2009
Source: Bri$a et al., Global and Biological Change, 2004
November 13
Dendroclimatology
Source: Intergovernmental Panel on Climate Change, 2007
SURFACE TEMPERATURERECONSTRUCTIONSFOR THE LAST 2 ,000 YEARS
NATIONAL RESEARCH COUNCILOF THE NATIONAL ACADEMIES
Tree-ring-derived records have played a prominent role in a!empts to establish how climate has varied in the recent past.
“ ”Jones et al.
The Holocene, 2009
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