The science and strategy of the Past Global Changes (PAGES) project

Available online at www.sciencedirect.com

Strategy paper

The science and strategy of the Past Global Changes (PAGES)projectLouise Newman1, Thorsten Kiefer1, Bette Otto-Bliesner2 and Heinz Wanner3

The Past Global Changes (PAGES) project was founded in 1991

with the mission to address past changes in the Earth System in

a quantitative and process-oriented way in order to improve

projections of future climate and environment, and inform

strategies for sustainability. Toward this goal, PAGES has

identified four sets of questions aimed at developing a better

understanding of climate–environment sensitivity, regional

variability, global system behavior and human interaction with

climate and environment. These questions are addressed by

scientific Working Groups that hold workshops and other

activities, toward the production of syntheses and products.

Furthermore, PAGES supports the international paleoscience

community by fostering collaboration and communication, and

ensuring access to and dissemination of results, data, and

other relevant information.

Addresses1 PAGES International Project Office, Zahringerstrasse 25, Bern 3012,

Switzerland2 Climate Change Research Section, Climate and Global Dynamics

Division, National Center for Atmospheric Research, United States3 Oeschger Centre for Climate Change Research (OCCR) and NCCR

Climate and Institute of Geography, Climatology and Meteorology,

University of Bern, Hallerstrasse 12, Bern 3012, Switzerland

Corresponding authors: Newman, Louise ([email protected]),

Kiefer, Thorsten ([email protected]), Otto-Bliesner, Bette

([email protected]) and Wanner, Heinz ([email protected])

Current Opinion in Environmental Sustainability 2010, 2:193–201

Received 16 February 2010; Accepted 21 April 2010

Available online 9th June 2010

1877-3435/$ – see front matter

# 2010 Elsevier B.V. All rights reserved.

DOI 10.1016/j.cosust.2010.04.004

Past global changes in contextWhat has happened can happen. This first-order principle

alone provides a good explanation as to why knowledge of

past changes leads to a better understanding of current

and future global change. The past does not provide a

prescriptive guide to the future, but can form the basis for

an evaluation of present day trends, future probabilities

and likely consequences for humans. More elaborately,

paleoscience (the study of climate and environmental

processes in the geologically recent past before the exist-

ence of instrumental records) provides the only way to

assess the operation of processes that act on timescales

longer than the instrumental record, and provide us with

www.sciencedirect.com

the long-term (natural) context for recent changes.

Further, paleodata can be used as benchmarks for model

skill assessment and, in concert with modeling of past

scenarios, provide a quantitative understanding of Earth

System variability and the underlying processes.

Given the magnitude of paleodata generated worldwide

on timescales from decades to millions of years, and the

diversity of disciplines involved, there is a clear need for

integration, coordination, and fast dissemination of results,

as well as an overarching scientific direction for paleore-

search. The founders of the Past Global Changes (PAGES;

www.pages-igbp.org/) project of the International Geo-

sphere–Biosphere Programme (IGBP; www.igbp.net/)

recognized this need. In 1991 they established a com-

munity-driven, international coordination and network-

ing project for paleoscience, which has since been jointly

supported by the Swiss and U.S. National Science

Foundations, and the National Oceanic and Atmos-

pheric Administration (NOAA). To this day, PAGES

remains the only component within the large program-

network of the Earth System Science Partnership

(ESSP, [1��]; www.essp.org/) that focuses specifically

on evidence from the past to inform current and future

global change.

PAGES is set up as an international effort to help stream-

line and promote past global change research. The scien-

tific aim is to identify the cutting-edge questions in

paleoscience and high-priority research needs, and to

ensure that they are addressed in a coherent manner. In

addition, capacity building, education and outreach are

an integral part of PAGES philosophy. PAGES is there-

fore a service-oriented project that works to promote

integrative research activities and support the inter-

national paleoscience community through fostering

collaboration and communication, and ensure access to

and dissemination of results, data, and other relevant

information. This is achieved by means of international

workshops and conferences, educational products and

outreach activities, publications, including the magazine-

style scientific newsletter, and the PAGES website

(www.pages-igbp.org/).

PAGES science planThe ultimate mission underlying all of PAGES efforts is

to address past changes in the Earth System in a quan-

titative and process-oriented way in order to improve

projections of future climate and environment, and


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194 Strategy paper

Figure 1

Overall structure and key elements of PAGES scientific emphasis. The

four Foci are complemented by four Cross-Cutting Themes that are of

relevance to all Foci and to paleoscience in general.

inform strategies for sustainability. PAGES is working

toward this mission by targeting four sets of key over-

arching questions developed from community feedback

and open discussions, discussions of the PAGES Scien-

tific Steering Committee, and the scientific knowledge

gaps identified in the IPCC AR4 WG1 [2].

These questions are encompassed within the PAGES

science structure (Figure 1; [3��]), and are addressed by

four thematic Foci, within which focused workshops and

other activities are organized to produce syntheses and

products that contribute to answering these questions.

Focus 1: climate forcingsFocus 1 fosters activities that aim to produce improved,

extended and consistent timeseries of climate forcing

parameters. Further, this Focus aims to quantitatively

understand the causes and impacts of variations in climate

forcings, including climate sensitivity and the carbon

cycle–climate feedback. The overarching questions

addressed in Focus 1 are: How did the main climate

forcing factors vary in the past? How sensitive was (and

is) the climate system to these forcings? What caused the

natural greenhouse gas and aerosol variations? To what

extent can paleodata constrain climate sensitivity and the

carbon cycle–climate feedback? In what precise sequence


and over what timescales did changes in forcings, climate,

and ecological systems occur?

Climate forcings are imposed radiative perturbations of

the Earth’s energy balance and can be of natural or

anthropogenic origin (see e.g. Figure 2). The sensitivity

of the climate system to an imposed forcing depends not

only on the magnitude and character of the climate

forcing externally imposed on the climate system

(primary forcings), but also on the feedbacks within the

climate system (secondary forcings), which amplify or

diminish the responses. Focus 1 addresses various issues

pertaining to both sets of forcings.

With regard to primary forcings, today’s challenges lie in

precisely tying together the timing of orbital solar insola-

tion changes with Earth System responses. Key questions

remain about the interplay between orbital parameter

configurations (obliquity, precession, eccentricity) and

different climate states (ice sheets and CO2) in driving

climate dynamics. Total solar irradiance operates on

shorter timescales than orbital parameters. A number of

proxies have been used to reconstruct past changes in

solar irradiance (e.g. sunspot number, length of solar

cycle, and cosmogenic isotopes of carbon and beryllium);

however, progress in understanding the cosmogenic sig-

natures is required before the solar forcing record can be

extended back through the Holocene (the last 11 600

years). Likewise, extension of the volcanic event record

through the Holocene will make a key contribution to our

understanding of the climatic effect of volcanic aerosols.

The secondary forcings (mineral dust, greenhouse gases,

land cover, sea ice, and continental ice and sea level), all

impact the radiative balance of the atmosphere but their

levels are dependent on the climate state through feed-

backs in the Earth System. Variations in mineral dust

aerosols absorb and scatter radiation, thereby affecting

the Earth’s radiative balance. As is true for the present,

there has been considerable regional variation of atmos-

pheric dust loading in the past (e.g. [4–6]); however, our

knowledge of the forcing effect of dust during past

periods, such as the Last Glacial Maximum (�21 000

years ago), is very low [2]. The greenhouse gas concen-

trations for past millennia are well known from ice core

analyses; however, key knowledge gaps remain. We need

to better understand the causes of natural fluctuations in

greenhouse gases, and the sensitivity of atmospheric CO2

to climatic changes. We also need to better constrain the

phasing between insolation, greenhouse gas concen-

trations and climate–environment responses. Changes

in land cover affect the dust loading of the atmosphere

and impact the water and carbon cycles. In addition, they

directly affect the radiative balance of the atmosphere

through altering the Earth’s albedo. Thus it is imperative

that we obtain better records and understanding of

regional changes in land use and cover through vegetation


Science and strategy of the PAGES project Newman et al. 195

reconstructions and other, indirect evidence (e.g. paleo-

fire activity, denudation, and soil erosion rates). A marine

counterpart to land cover is sea ice. It acts to modulate

atmospheric–ocean moisture, heat and gas exchange, and

perhaps most importantly, albedo, with diminishing sea

ice imposing a strong positive feedback on climate warm-

ing. Seasonal reconstructions of past changes in sea ice

cover are, however, problematic and require improve-

ment to enable quantification of the role of sea ice in

past climate change. Similarly, continental ice sheets

affect the Earth’s albedo, impact sea level (which in turn

modifies the land albedo), and represent a reservoir of

freshwater that when discharged affects oceanic and

atmospheric circulation, and the carbon cycle. Improved

reconstructions of the extension, geometry, and volume

of past ice sheets and of global and relative sea level are

therefore high priority in Focus 1.

Focus 2: regional climate dynamicsFocus 2 seeks to achieve a better understanding of past

regional climatic and environmental dynamics through

comparisons of reconstructions and model simulations.

Focus 2 addresses the following overarching questions:

How did regional climate and the Earth’s natural environ-

ment change in the past? What are the main patterns and

modes of climate variability on subdecadal to orbital

timescales? How do climate variability and extreme

events relate to the mean state of the climate system?

The focus of paleoclimatology is expanding from the

detection and attribution of present climate change, to

encompass clarification of regional (e.g. continental

and subcontinental) expressions of past climate and

environmental changes (e.g. [7]). Information on

regional-scale past climate dynamics allows us to charac-

terize amplitudes and rates of change at subcontinental

scales relevant to societies. Furthermore, it provides a

context for observed climatic–environmental change,

long-term records to analyze multidecadal and slower

processes, and benchmark scenarios for general circula-

tion models. Studies in Focus 2 include multiproxy

reconstructions of the key climate parameters, and

transient paleo-runs with models of different complex-

ity and resolution.

Advances in modeling techniques, which now allow

atmosphere–ocean–biosphere coupling, high spatial

resolution, transient runs, and representation of climate

modes [8,9], have increased the need for regional proxy

datasets that are well-dated, of high resolution and care-

fully calibrated [10]. New analytical techniques have

increased the array of proxies and archives used for

paleoscientific studies, forming an increasingly rich base

for data synopsis and data-model comparisons. However

reconstructions are biased toward the northern mid-lati-

tudes, and there is uncertainty about the performance of

the various reconstruction techniques, and a lack of


complete understanding of the dynamics that drive

regional changes and their far-field interconnectedness

(teleconnections).

Despite significant progress over the last few decades, we

still do not sufficiently understand the precise sequence

of changes related to regional climate forcings, internal

variability, system feedbacks, and the sensitivities and

responses of surface climate, land cover and biosphere

and hydrosphere. Moreover, many parts of the globe lack

adequate paleorecords for comparison with model simu-

lations, and high-resolution (spatially and temporally)

instrumental datasets are sparse. This is particularly true

or the Southern Hemisphere and the tropics. Thus, a key

goal of this Focus is to develop datasets that describe the

patterns of past climate change at the regional scale,

including the major climate state for the last 2000 years,

and wherever possible throughout the last glacial cycle

(last 130 000 years).

Focus 2 also has a methodological component that was

designed to tackle issues relating to reconstruction

methods developed for the last millennia, with the aim

to reduce uncertainties and biases. The improved re-

construction methods may ultimately also be employed

on longer timescales during the Holocene and the last

glacial cycle. Further, Focus 2 will support improve-

ments in model development and data-model compari-

son approaches, to better constrain the drivers and

mechanisms of regional climate change on different

timescales.

Focus 3: global Earth System dynamicsFocus 3 looks at large-scale interactions between com-

ponents of the Earth System (e.g. atmosphere, biosphere,

cryosphere, and hydrosphere), and the links between

regional-scale and global-scale changes. Further, it

addresses global-scale abrupt and gradual Earth System

changes and their underlying processes, including their

response to changes in forcings, internal feedbacks, and

teleconnections. The overarching questions addressed by

this Focus are: How do large-scale changes in the Earth

System affect regional climatic and environmental con-

ditions? How have regions or Earth System components

interacted to produce climate and environmental vari-

ations on a global scale? What are the causes and

thresholds of rapid transitions between quasi-stable cli-

matic and environmental states, in particular on time-

scales that are relevant to society, and how reversible are

these changes?

The scope of Focus 3 is broad and is thus broken down

into four themes, on the hydrological cycle, rapid climate

changes, interglacial variability, and ocean biochemistry.

The variability of the hydrological cycle is of key

importance to terrestrial ecosystems, plays a crucial role


196 Strategy paper

in large-scale energy transport, and partly controls climate

sensitivity. Furthermore, the detrimental effects associ-

ated with perturbations of the hydrological cycle (drought

and flooding) are of major concern with respect to future

climate change. However, projections of, for example,

future precipitation changes disagree in magnitude and

sign of the anticipated change in low-latitude terrestrial

areas [11]. The largest natural variation of the hydrolo-

gical cycle at a global scale is associated with the monsoon

systems. While the temporal evolutions of the regional

monsoon systems are generally known, large uncertain-

ties exist with respect to the sequence or phasing of their

response to global forcings, and the potential interaction

with interannual modes of climate variability remains to

be quantified. Thus, research in this theme aims to

unravel the mechanisms that caused variations in both

the global and regional monsoon systems, and to identify

and understand teleconnections, both between monsoon

components and with other components of the climate

system.

Rapid climate change has occurred naturally in the past.

The climate of the last glacial period (�75 000–10 000

years ago) is characterized by rapid changes, with

repeated warmings of up to 158C within decades in

Greenland [12], and gradual, out-of-phase counterparts

in the Southern Hemisphere [13]. Changes in ocean heat

transport have been employed to explain these events

[14,15], predominantly through modification of the mer-

idional overturning circulation (MOC) from freshwater

forcing. Yet there is considerable controversy over the role

of MOC changes in climate variability during the glacial

period, and also during the Holocene [16,17]. The chal-

lenge remains to produce and compile well-dated records

of centennial-scale to millennial-scale oceanographic and

climatic change from the Holocene, last glacial period and

previous interglacials. Furthermore, characterization of

the rate of abrupt changes, and assessment of hypotheses

on the drivers and effects of past MOC changes, are key

issues that require attention in order to inform assess-

ments of the possibility and potential impacts of such

changes in the future.

A further theme aims to understand aspects of the current

interglacial, the Holocene, by analyzing the drivers of

climate variability within and between past interglacials.

The interglacials of the last 800 000 years differ consider-

ably in amplitude, length, and trajectory (Figure 3).

Investigations of glacial–interglacial change show that

seasonal and latitudinal variations in insolation drive

the observed climatic changes [18], while amplification

(through albedo and greenhouse gas changes; [19,20�]) is

essential in modulating the strength of the warmings. To

understand the underlying drivers of interglacial climate

variability and hence learn about the stability of current

conditions, activities under this theme aim to compile and

analyze the spatial pattern of each interglacial. Knowl-


edge of past interglacials can also provide constraints for

the potential for future large-scale changes in ice sheet

extent and the rate of resulting sea level rise; and is thus

another issue addressed within this theme.

Paleoperspectives on ocean biogeochemistry is another

Focus 3 theme, and addresses ocean-wide changes (e.g.

nutrient cycling and ocean acidification) that potentially

have strong climatic feedbacks and socioeconomic

effects. Owing to the complexity of the coupled chem-

istry–biology system, it is currently unclear what effect a

warming world with increasing CO2 levels and changing

nutrient availability and ocean chemistry, will have on

marine ecosystems at a global scale and how these will

feedback on global climate. It is thus critical to under-

stand the nutrient cycle and efficiency of the marine

biological pump under different climatic boundary con-

ditions in the past. Furthermore, it is imperative to

quantify the response of marine organisms and ecosys-

tems to acidification by studying past perturbations of the

carbon cycle and examples from high-CO2 worlds in

Earth history. Presently, few datasets are comprehensive

enough to inform on global-scale issues relating to ocean

biogeochemistry. It therefore remains an important step

to compile proxy evidence for past global changes in, for

example, the oceanic nitrogen, carbon, and iron cycles

during climate transitions, and to unravel the mechanisms

causing the variations.

Focus 4: past human–climate–ecosysteminteractionsThis Focus addresses the long-term interactions among

past climate conditions, ecological processes, and human

activities during the Holocene, including the last few

centuries where people perturbed the environment on a

large scale (coined as the ‘Anthropocene’). In doing so, it

tackles the following overarching questions: What are the

historical patterns of human interactions with climate

change and ecological processes? How can we learn from

past patterns and interactions in order to better under-

stand and manage natural ecosystems at present and in

the future?

The majority of the Earth’s surface has a history of human

impact that is significant in terms of duration and/or

intensity. Therefore, integrated strategies of preser-

vation, conservation, or sustainable management of eco-

systems demand information about how human activities

have interacted with natural ecosystems in the long term

[21]. In recent decades there have been rapid advances in

our ability to reconstruct past ecological change (e.g. [22–25]), and reconstructions are increasingly revealing the

complexity of coupled human–climate–ecology systems

(e.g. Figure 4).

At global to continental scales, new syntheses of data

records are required to test theories of climate forcing, to



Figure 2

Timeseries representing the most relevant forcings of long-term climate variability over the last 1.4 million years. (a) High (red) and low (blue) June

solstice irradiance [26]; (b) land cover changes indicated by % tree pollen [27]; (c) changes in marine d18O as an indicator of changes in relative sea

level [28]; (d) variations in CO2 recorded by Antarctic ice cores [20�]; (e) changes in dustiness, recorded by Antarctic ice cores (based on [29]); (f)

changes in Southern Ocean winter sea ice cover reconstructed from diatom assemblages [30].

provide new quantitative data for biogeochemical cycles,

to provide driving mechanisms of predictive models, to

strengthen the knowledge basis of human–environment

interactions, and to search for nonlinear behavior that may

have implications for future Earth trajectories. At regional

to local scales, new syntheses are needed to provide long-


term perspectives on ecosystem response to climate and

human activities, to help define reference conditions,

conservation goals and restoration targets, to help define

the spatial variability of ecosystem trajectories, and to

provide the means to drive and validate local process-

based predictive models.


198 Strategy paper

Figure 3

The evolution of Antarctic temperature (represented by deuterium content of the ice) across a selection of interglacials. Data are shown as 1000-year

averages, based on [31]. Interglacials can be warm or cool, long or short, and vary in shape. MIS = Marine Isotope Stage. Figure compiled by E Wolff.

With the aim to understand ecosystem change on differ-

ent timescales and at spatial scales ranging from local to

global, Focus 4 will tackle the themes of land cover and

use, the carbon cycle, biodiversity, water resources, and

Figure 4

Reconstructed landscape stability in the Lake Erhai catchment, SW China, s

system. The timeseries for ‘disturbed land’ and ‘soil erosion’ from 2960 cali

phase space. The stable ‘steady state’ before 1433 cal a BP (green), progres

degraded ‘steady state’ (red) after 800 cal a BP. T1 and T2 represent likely

show possible future trajectories of landscape recovery depending on land

modern system. From [32�].


soil and sediment, and will integrate paleoenvironmental

records of these components, within and between

regions. This will enable quantification of the nature of

human activities that have influenced the functioning of

howing possible alternative steady states of the coupled soil–land cover

brated years before present (cal a BP) to present are plotted together in

ses through a 600-year transition period before settling into the modern

positions of major thresholds in the system. The dashed arrows from T2

management but demonstrate the essentially irreversible state of the



ecological systems (e.g. irrigation practices), and clarifica-

tion of the feedbacks from human activities to the climate

system (e.g. deforestation). It will also facilitate under-

standing of how human and climate impacts have inter-

acted with internal system dynamics, and provide a better

estimate of the sensitivity and resilience of modern

ecological systems to new or increased stresses from

human activities and climate change. Ultimately, the

synthesis and integration of this information will help

develop appropriate sustainable management strategies,

such as determining the historical range of variability in

natural disturbance regimes, the reference conditions that

are most relevant for ecosystem restoration, or the land

use that appears most appropriate in the face of projected

change.

The science of Focus 4 is also relevant to and impacted by

societal aspects. Thus, PAGES, in collaboration with the

IGBP core project Analysis, Integration and Modeling of

the Earth System (AIMES) and the International Human

Dimensions Programme (IHDP), developed the joint

research initiative Integrated History and Future of

People on Earth (IHOPE). IHOPE seeks to better under-

stand the dynamic interactions between all aspects of

human behavior and the environment by integrating the

social science elements into Earth System understanding.

In particular, questions targeting aspects of socio-ecologi-

cal resilience, the role of technology in socio-ecological

systems, and the adaptability of these systems to long-

term environmental change, will be addressed within the

scope of IHOPE science.

Cross-Cutting ThemesIn addition to addressing scientific issues specific to

Earth System changes, PAGES also recognizes the need

for focused research into paleoscientific methods and

techniques. Four Cross-Cutting Themes (CCTs) on

chronology, proxies, modeling, and data have therefore

been identified (Figure 1) with the aim to improve the

‘toolbox’ available to paleoscientists. First, dating is an

issue that underlies all paleoscientific records, thus the

CCT 1 Chronology organizes activities to improve

absolute and relative dating tools and facilitate the de-

velopment of reference timescales. Second, variations in

past climatic and environmental parameters (e.g.

temperature, precipitation, and vegetation cover) must

be reconstructed indirectly from ‘proxies’. CCT 2 ProxyDevelopment, Calibration, and Validation therefore aims to

improve the precision, accuracy, and interpretation of

proxies as a basis for high-quality reconstructions to

complement instrumental data. Third, modeling of past

scenarios is key to quantitatively explore Earth System

couplings and feedbacks. CCT 3 Modeling aims to

improve model components for the simulation of past

scenarios and for better comparison with proxy data.

Fourth, with the growing amount of paleodata being

generated and the increasing need for integration and


synthesis, data sharing is becoming increasingly import-

ant. CCT 4 Data Management was developed to improve

the availability and access to paleoscientific data and

optimize cooperation between the scientific community

and data centers.

ConclusionsThe science addressed in PAGES has recently been

reorganized into the four scientific Foci and CCT out-

lined above (Figure 1; [3��]). The future efforts of PAGES

will be directed to implementation of the goals described

within this framework, toward the ultimate objective of

addressing past changes in the Earth System in a quan-

titative and process-oriented way in order to improve

projections of future climate and environment, and

inform strategies for sustainability.

Scientific Working Groups play a key role in PAGES

implementation strategy by targeting specific issues out-

lined in the Foci through focused workshops and activi-

ties, ultimately producing synthesis products, such as

major publications and datasets.

The science questions addressed by the PAGES

paleoscience community were chosen because of their

relevance to concerns about current and future global

change. Accordingly, related questions are also addressed

by communities working on contemporary timescales,

such as the programs and projects of the ESSP. PAGES

therefore plays a central role in integrating the themes of

the other IGBP core projects, and actively seeks linkages

and collaborations within the other programs of the ESSP

(e.g. WCRP-CLIVAR), with the aim toward building a

worldwide, integrative past global change community.

The bundling of research institutions and scientists

within an international network leads to more robust,

balanced, and globally relevant paleoscience.

The need for a holistic and coordinated approach to global

change science is well documented (e.g. [1��]). With an

expanding number of individual scientists and research

groups/projects all striving to address key questions in

global change science, a key value of PAGES lies in its

ability to coordinate and streamline efforts and resources.

Through organization and support of focused and inter-

national workshops and meetings, PAGES integrates

across spheres, timescales, resource levels, and disciplines

to produce fundamentally important and societally

relevant scientific results.

AcknowledgementsThe Swiss National Science Foundation, the National Science Foundationand National Oceanic and Atmospheric Administration, and theInternational Geosphere–Biosphere Programme are thanked for their long-terms support of PAGES; the University of Bern, Switzerland for their in-kind support. The authors acknowledge the contributions of the PAGESScientific Steering Committee to the science and discussions presentedherein.


200 Strategy paper

References and recommended readingPapers of particular interest, published within the period of review,have been highlighted as:

� of special interest�� of outstanding interest

1.��

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This paper describes the motivation, goals and approaches of the EarthSystem Science Partnership (ESSP). As a core project of the InternationalGeosphere–Biosphere Programme (IGBP), the Past Global Changes(PAGES) project is part of the large ESSP network.

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3.��

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13. EPICA Community Members: One-to-one coupling of glacialclimate variability in Greenland and Antarctica. Nature 2006,444:195-198.


14. Stocker TF, Johnsen SJ: A minimum thermodynamic modelfor the bipolar seesaw. Paleoceanography 2003, 18: articlenumber 1087.

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16. Bond G, Showers W, Cheseby M, Lotti R, Almasi P, deMenocal P,Priore P, Cullen H, Hajdas I, Bonani G: A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates.Science 1997, 278:1257-1266.

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20.�

Luthi D, Le Floch M, Bereiter B, Blunier T, Barnola J-M,Siegenthaler U, Raynaud D, Jouzel J, Fischer H, Kawamura K et al.:High-resolution carbon dioxide concentration record 650,000–800,000 years before present. Nature 2008, 453:379-382.

This paper presents and discusses the latest extension of the record ofpast atmospheric CO2 concentration from measurements on air bubblesfrom an Antarctic ice core. These data are key for the many quantitativestudies of past climate, including those within PAGES Focus 1 on ClimateForcings that aim to constrain climate sensitivity and the carbon cycle/climate feedback.

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http://www.pages-igbp.org/cgi-bin/WebObjects/products.woa/wa/product%3Fid=346



http://dx.doi.org/10.1029/2005JD006653

http://dx.doi.org/10.1029/2005GL023596

http://dx.doi.org/10.1029/2004PA001071


32.�

Dearing JA: Landscape change and resilience theory: apalaeoenvironmental assessment from Yunnan, SW China.Holocene 2008, 18:117-127.

This paper is a case study on the effects of land use and climate on thestability of the landscape over decadal–millennial timescales. Analysis of


3000-year long reconstructions of land use and erosion in a river catch-ment in China suggests the systematic existence of alternative steadystates in the landscape. The study is a good example of the kind ofscience addressed in PAGES Focus 4 on past human–climate–ecosys-tem interactions.


Documents

The science and strategy of the Past Global Changes (PAGES) project