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Source: St. George and Luckman, 2001
Source: St. George and Luckman, 2001
Source: St. George and Luckman, 2001
PRINCIPLE COMPONENTS ANALYSIS
a.k.a. Empirical Orthogonal Function analysis
PC2 (group 2)
PC3 (group 3)
PC1 (group 1)
Source: St. George and Luckman, 2001
Source: St. George and Luckman, 2001
Source: St. George and Luckman, 2001
most sites
Source: St. George and Luckman, 2001
most sites
farthestnorth
Source: St. George and Luckman, 2001
most sites
unusualsite
farthestnorth
LINEARREGRESSION
yt = axt + b + ε
Tjj = 0.23PC1 + -0.23PC3t+1 + 0.16PC2t+1 + -0.09PC1t+1 + -0.46
Source: St. George and Luckman, 2001
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
“”
Photograph: Marianna
G L O B A L T E M P E R AT U R E R E C O N S T R U C T I O N S
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 Briffa, 2006
...this study provides evidence for intervals of significant warmth in the [Northern Hemisphere] within the so-called Medieval Warm Period and for significantly colder intervals during the so-called Li!le Ice Age period.
— Osborne and Briffa, 2006
“
”
LINEARREGRESSION
Source: Intergovernmental Panel on Climate Change, 2007
Photograph: Mark Anbinder
Tree-rings also allow the reconstruction of large-scale regional or global temperature pa!erns defined by large networks of chronologies.
— Brian Luckman
“”
Source: Briffa et al., Global and Planetary Change, 2004
h"p://www.cru.uea.ac.uk/cru/people/briffa/temmaps/
1883“THE LOUDEST SOUND IN MODERN HISTORY”
Krakatau, Indonesia 1883
h"p://www.cru.uea.ac.uk/cru/people/briffa/temmaps/
1816THE “YEAR WITHOUT A SUMMER”
Mount Tambora, Indonesia Its eruption in 1815 was the most explosive since AD 180
Source: Briffa et al., Global and Biological Change, 2004
h"p://www.cru.uea.ac.uk/cru/people/briffa/temmaps/
Huaynaputina Peru
“Trees are not thermometers or rain gagues.” Keith Briffa and colleagues
THED I V E R G E N C E
PROBLEM
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.
— Jones et al., The Holocene, 2009
“”
Source: Briffa et al., Global and Biological Change, 2004
Source: D’Arrigo et al., 2008
SURFACE TEMPERATURERECONSTRUCTIONSFOR THE LAST 2 ,000 YEARS
NATIONAL RESEARCH COUNCILOF THE NATIONAL ACADEMIES
