geog5839.19, dendroclimatology

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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