GLOBAL International Geosphere-Biosphere Programme IGBP Science 4 CHANGE gas gases asulphate aerosols 20194019601980 YEAR modcation generaly more uding rangelands,open owent pst penuton areas, wetands: eed by humans for millennia: rjectories of change aconnt state of flux hgenety: landscape on important as poecies responses to changes in otes and policies, with ad o-oconomicrger ovent trom remot u oted by gobz ggobel interplay and diversi Global Change and the Earth System: A planet under pressure The Global Environmental Change Programmes
IGBP Science 4 The Global Environmental Change Programmes
ForewordTheworldfacessignificantenvironmentalproblems:shortagesof cleanandaccessiblefreshwater,degradation of terrestrial and aquaticecosystems,increasesin soil erosion,loss of biodiversity,changes in the chemistry of theatmosphere,declines in fisheries,and the possibility of significant changes in climate.Thesechanges are occurring over and above the stresses imposed by the naturalvariability of adynamic planet andareintersecting with the effects of past andexistingpatterns of conflict,poverty,disease,andmalnutrition.Thechanges taking place are,infact, changes in the human-naturerelationship. They are recent, they are profound, and many are accelerating.They are cascading through the Earth's environment in ways that are difficult tounderstandand often impossible to predict.Surprises abound.At least,thesehuman-driven changes to the global environment will require societies to developa multitudeof creative responseand adaptation strategies. Some are adaptingalready;most are not.At worst,they may drivethe Earth itself into a differentstatethatmaybemuch less hospitableto humans and otherforms of life.As global environmental changeassumes amore central place in humanaffairs,science is being thrust into the unfamiliar and uncomfortable role of a majorplayer in a heated and potentially divisive international debate about the natureand severity of global change and its implications for ways of life. Much is at stakeandthegame is beingplayedhard,Despitetherisks,sciencemust accepttheresponsibilityofdeveloping and communicating the essential knowledgebasethatsocieties can use to debate, consider and ultimately decide on how to respondto global change.Thepast decade of global changeresearch,summarised in this booklet,hasunveiled more and more about the complex and interrelated nature of the EarthSystem, and about the ways in which human activities are impacting the System.Much excitingsciencehasbeen carried outandmuchhasbeenachieved.Aboveall,weknowthattheEarthSystemhasmovedwelloutsidetherangeofnaturalvariability exhibited overthe last halfmillion years at least.Thenature of changesnowoccurringsimultaneouslyintheglobal environment,theirmagnitudes andrates,are unprecedented in human history,and probably in the history of theplanet. The Earth is now operating in a no-analogue state.On the other hand, we do not yet know where critical thresholds may lie.Nor can we sayif,when andhowthe increasing human enterprisewill propel theEarth Systemtowards and across theboundaries to different states of theglobalenvironment.We also do notknow the features or operating modes of the EarthSystem that are particularly robust, which when combined with human ingenuity-with creative technological, institutional and ethical development-might lead toasafetransition to sustainability.Global change science has contributed much to anunderstandingof theEarthSystem butthereismuchto bedone.The challenge of ensuring a sustainable future is daunting and it is immediateThechallengeCANbemet, but onlywithanewand evenmorevigorous approachtoanintegrated EarthSystem science.This summary represents a small but importantsteptowards confrontingthe future,towards building an integrated Earth Systemscience and towards meeting the great challenge of global sustainability.Arild UnderdalBerrienMooreIIIPeter LemkeMichel LoreauChair, IGBPChair, IHDPChair, WCRPCo-Chair, DIVERSITAS
The world faces signifi cant environmental problems: shortages of clean and accessible freshwater, degradation of terrestrial and aquatic ecosystems, increases in soil erosion, loss of biodiversity, changes in the chemistry of the atmosphere, declines in fi sheries, and the possibility of signifi cant changes in climate. These changes are occurring over and above the stresses imposed by the natural variability of a dynamic planet and are intersecting with the effects of past and existing patterns of confl ict, poverty, disease, and malnutrition. The changes taking place are, in fact, changes in the human-nature relationship. They are recent, they are profound, and many are accelerating. They are cascading through the Earth’s environment in ways that are diffi cult to understand and often impossible to predict. Surprises abound. At least, these human-driven changes to the global environment will require societies to develop a multitude of creative response and adaptation strategies. Some are adapting already; most are not. At worst, they may drive the Earth itself into a different state that may be much less hospitable to humans and other forms of life. As global environmental change assumes a more central place in human affairs, science is being thrust into the unfamiliar and uncomfortable role of a major player in a heated and potentially divisive international debate about the nature and severity of global change and its implications for ways of life. Much is at stake and the game is being played hard. Despite the risks, science must accept the responsibility of developing and communicating the essential knowledge base that societies can use to debate, consider and ultimately decide on how to respond to global change. The past decade of global change research, summarised in this booklet, has unveiled more and more about the complex and interrelated nature of the Earth System, and about the ways in which human activities are impacting the System. Much exciting science has been carried out and much has been achieved. Above all, we know that the Earth System has moved well outside the range of natural variability exhibited over the last half million years at least. The nature of changes now occurring simultaneously in the global environment, their magnitudes and rates, are unprecedented in human history, and probably in the history of the planet. The Earth is now operating in a no-analogue state. On the other hand, we do not yet know where critical thresholds may lie. Nor can we say if, when and how the increasing human enterprise will propel the Earth System towards and across the boundaries to different states of the global environment. We also do not know the features or operating modes of the Earth System that are particularly robust, which when combined with human ingenuity - with creative technological, institutional and ethical development - might lead to a safe transition to sustainability. Global change science has contributed much to an understanding of the Earth System but there is much to be done. The challenge of ensuring a sustainable future is daunting and it is immediate. The challenge CAN be met, but only with a new and even more vigorous approach to an integrated Earth System science. This summary represents a small but important step towards confronting the future, towards building an integrated Earth System science and towards meeting the great challenge of global sustainability. Berrien Moore III Arild Underdal Peter Lemke Michel Loreau Chair, IGBP Chair, IHDP Chair, WCRP Co-Chair, DIVERSITAS Foreword
ContentsIGBPSCIENCENo.4Foreword2·ScienceHighlights4·AnIntegratedEarthSystemThe human-nature relationshipThe Earth as a systemGlobal Change7.PlanetaryMachineryRole of the biosphereTemporal variabilityLinkagesand connectivitiesAbrupt changes and critical thresholds11·TheAnthropoceneEraThe nature of global changeDrivers of changeAn Earth System perspective15·Reverberations of ChangeLong-term perspectivesCascading impactsInteracting processes and feedbacks19·LivingwithGlobal ChangeAnticipating the consequencesMultiple,interacting effectsRisks for the Earth System23·MakingEarthSystem ScienceThe dawn of a new eraQuestions at the frontierCoping with complexity and irregularityThe Earth System toolkit27TowardsGlobalSustainability?Good management of the Earth SystemAdvancing sectoral wisdomGlobal science for global sustainability30·Challenges of a changing Earth31 ·Appendix:About the Global Enviromental Change Programmes1IGBP SCIENCE No. 4
IGBP SCIENCE No. 4 1 • Foreword 2 • Science Highlights 4 • An Integrated Earth System The human-nature relationship The Earth as a system Global Change 7 • Planetary Machinery Role of the biosphere Temporal variability Linkages and connectivities Abrupt changes and critical thresholds 11 • The Anthropocene Era The nature of global change Drivers of change An Earth System perspective 15 • Reverberations of Change Long-term perspectives Cascading impacts Interacting processes and feedbacks 19 • Living with Global Change Anticipating the consequences Multiple, interacting effects Risks for the Earth System 23 • Making Earth System Science The dawn of a new era Questions at the frontier Coping with complexity and irregularity The Earth System toolkit 27 • Towards Global Sustainability? Good management of the Earth System Advancing sectoral wisdom Global science for global sustainability 30 • Challenges of a changing Earth 31 • Appendix: About the Global Enviromental Change Programmes IGBP SCIENCE No. 4 Contents
ScienceHighlightsIGBPSCIENCE No.4Somewhatmore than a decade ago it was recognised that the Earthbehavesas a system in which the oceans, atmosphere and land, and the living andnon-living parts therin, were all connected.While accepted by many, thisworkinghypothesis seldomformed the basis forglobal changeresearch.Littleunderstandingexisted of howthe Earth worked as a system,how the partswereconnected,or even abouttheimportance ofthevarious componentpartsof the system.Feedback mechanisms were not always clearly understood,norwerethedynamicscontrollingthesystemOvertheinterveningyearsmuchhasbeenlearned.Inmanyrespectsformeruncertaintiesaboutthenatureandfuturecourseofglobalchangehavebeenreduced.In others,the realisation that uncertaintyis an inherentpart of thesystemhasgainedcredence.Overthelast10yearstheunderstandingofhowhumans are bringing aboutglobal change has undergone a quantum jumpAttempts to separate natural and anthropogenicallyinduced variabilityin theEarthSystemhaveprovedtobesuccessfulinmanyrespects.Thedecadehasbeenoneof scientificchallenge.achievementandexcitementThe scientific landscapeis very different nowfrom that of the late1980sIn general,global change research has confirmed many of thehypothesesand much of the sketchy understanding of a decade ago, adding a wealth ofquantitative detail and process-level understanding at all scales.Largely througha significant increase in the ability to unravel the past,the understanding of thenatural dynamics of the Earth System has advanced greatly.It is now clear thatglobal change is one oftheparamount environmental issuesfacinghumankindatthebeginningofthenewmillennium.Thetaskof synthesisingadecadeofglobalchangeresearchhasbeendaunting, but the rewards have been great. Detailed results and individualreferencescannotbepresented here.Thesemustbesoughtfromtheindividualcore project syntheses and the IGBP-wide synthesis, soon to be publishedby SpringerVerlag intheIGBPbook series.Inthis summaryonlygeneralisedhighlights are presented, the so-called big-picture findings.They are based ondetailed,quantitativesciencethathasbeen published by a multitudeofscientistsworking worldwide over the past 1o years and longer.Major research findings:The Earth is a system that life itself helps to control. Biologicalprocesses interact strongly with physical and chemical processes tocreatethe planetary environment, but biology plays a much strongerrole than previously thought in keeping Earth's environment withinhabitable limits.Global change is much more than climate change. It is real, it ishappening nowand it is accelerating.Human activities are significantlyinfluencingthefunctioningoftheEarthSysteminmanyways;anthropogenicchanges are clearly identifiable beyond natural variability and are equal tosome of thegreat forces of naturein theirextent andimpact.IGBP SCIENCE No. 4Science Highlights
2 IGBP SCIENCE No. 4 Science Highlights Science Highlights IGBP SCIENCE No. 4 Somewhat more than a decade ago it was recognised that the Earthbehaves as a system in which the oceans, atmosphere and land, and the living and non-living parts therin, were all connected. While accepted by many, this working hypothesis seldom formed the basis for global change research. Little understanding existed of how the Earth worked as a system, how the parts were connected, or even about the importance of the various component parts of the system. Feedback mechanisms were not always clearly understood, nor were the dynamics controlling the system. Over the intervening years much has been learned. In many respects former uncertainties about the nature and future course of global change have been reduced. In others, the realisation that uncertainty is an inherent part of the system has gained credence. Over the last 10 years the understanding of how humans are bringing about global change has undergone a quantum jump. Attempts to separate natural and anthropogenically induced variability in the Earth System have proved to be successful in many respects. The decade has been one of scientifi c challenge, achievement and excitement. The scientifi c landscape is very different now from that of the late 1980s. In general, global change research has confi rmed many of the hypotheses and much of the sketchy understanding of a decade ago, adding a wealth of quantitative detail and process-level understanding at all scales. Largely through a signifi cant increase in the ability to unravel the past, the understanding of the natural dynamics of the Earth System has advanced greatly. It is now clear that global change is one of the paramount environmental issues facing humankind at the beginning of the new millennium. The task of synthesising a decade of global change research has been daunting, but the rewards have been great. Detailed results and individual references cannot be presented here. These must be sought from the individual core project syntheses and the IGBP-wide synthesis, soon to be published by Springer Verlag in the IGBP book series. In this summary only generalised highlights are presented, the so-called big-picture fi ndings. They are based on detailed, quantitative science that has been published by a multitude of scientists working worldwide over the past 10 years and longer. Major research fi ndings: • The Earth is a system that life itself helps to control. Biological processes interact strongly with physical and chemical processes to create the planetary environment, but biology plays a much stronger role than previously thought in keeping Earth’s environment within habitable limits. • Global change is much more than climate change. It is real, it is happening now and it is accelerating. Human activities are signifi cantly infl uencing the functioning of the Earth System in many ways; anthropogenic changes are clearly identifi able beyond natural variability and are equal to some of the great forces of nature in their extent and impact. 4 glacial cycles recorded in the Vostok ice core J.R. Petit et al., Nature, 399, 429–36, 1999. Age (kyr BP) inferred temperature °C ppmv CO2 ppbv CH2 280 260 240 220 200 700 600 500 400 -8 -6 -4 -2 0 2 4 400 300 200 100 350 250 150 50 0 Northern Hemisphere Average Surface Temperature 1000 1200 1400 1600 1800 2000 Year Temperature Anomaly (°C) 1.0 0.5 0.0 -0.5 -1.0 1998 Mann et al. 1999: Geo. Res. Let.,26, 6, 759 reconstruction (AD 1000-1980) raw data (AD 1902-1998) calibration period (AD 1902-1980) mean reconstruction (40 year smooothed) linear trend (AD 1000-1850) Nitrogen Year "Natural" N fixation Anthropogenic N fixation Global N fixation (Tg/yr) 150 100 50 0 1920 1940 1960 1980 2000 Human Population Billions of people 7000 5000 3000 1000 1000 8 B.C. A.D. 4 6 2 0 Species Extinctions Years Number of extinct species Mammal species Birds 60 20 0 50 40 0 1600 -1649 1650 -1699 1700 -1749 1750 -1799 1800 -1849 1850 -1899 1900 -1959 CO2 Year AD CO2 concentration (µL/L) 0 500 1000 1500 2000 350 300
Science HighlightsIGBPSCIENCENo.4The human enterprise drives multiple,interacting effects thatcascade throughthe Earth System in complex ways.Global changecannotbeunderstood interms ofa simplecause-effectparadigm.Cascadingeffects of human activities interact witheach other and with local-andregional-scale changes in multidimensional ways.The Earth's dynamics are characterised by critical thresholdsand abrupt changes. Human activities could inadvertently triggerchanges with catastrophic consequences for the Earth System.Indeed,itappearsthat sucha changewas narrowlyavoided inthecaseofdepletion of the stratospheric ozonelayer.TheEarth System has operatedin different quasi-stable states, with abrupt changes occurring betweenthem overthelasthalf millionyears.Human activitiesclearlyhavetheApotential to switch theEarth System to alternative modes of operationthatmayproveirreversible.4oThe Earth is currently operating in a no-analogue state. In terms ofkey environmental parameters,the Earth System has recentlymoved welloutsidetherangeofthenaturalvariabilityexhibitedoveratleastthelasthalfmillion years.Thenature of changesnow occurringsimultaneouslyin theEarth System,their magnitudes and rates of cbange areunprecedentedThese scientific results lead directly to two important conclusions, one forthenatureofthesocietalresponserequiredtoaddressglobalenvironmentalchange andthe otherforthetypeof science neededto understandtheEarth System.Ethics of global stewardship and strategies for Earth Systemmanagement are urgently needed. The inadvertent anthropogenictransformationoftheplanetaryenvironmentis,ineffect,alreadyaformofmanagement, or rather mismanagement.It is not sustainable.Therefore,thebusiness-as-usual way ofdealingwiththe Earthhastobereplaced-as soonas possible -by deliberate strategies of good management.A novel system of global environmental science is emerging. The0largely independent efforts of various international research programmes andnumerous national projects create thebasisfor an Earth System sciencethatis capable of tackling thecognitivetasks suggested by the research findingsatabove.Thisnewsciencewill employinnovativeintegrationmethodologiesorganize itself intoa global system with transnational infrastructures, andembark on a continuing dialoguewith stakeholders around theworld3Science HighlightsIGBP SCIENCE No. 4
Science Highlights IGBP SCIENCE No. 4 3 IGBP SCIENCE No. 4 Science Highlights • The human enterprise drives multiple, interacting effects that cascade through the Earth System in complex ways. Global change cannot be understood in terms of a simple cause-effect paradigm. Cascading effects of human activities interact with each other and with local- and regional-scale changes in multidimensional ways. • The Earth’s dynamics are characterised by critical thresholds and abrupt changes. Human activities could inadvertently trigger changes with catastrophic consequences for the Earth System. Indeed, it appears that such a change was narrowly avoided in the case of depletion of the stratospheric ozone layer. The Earth System has operated in different quasi-stable states, with abrupt changes occurring between them over the last half million years. Human activities clearly have the potential to switch the Earth System to alternative modes of operation that may prove irreversible. • The Earth is currently operating in a no-analogue state. In terms of key environmental parameters, the Earth System has recently moved well outside the range of the natural variability exhibited over at least the last half million years. The nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change are unprecedented. These scientifi c results lead directly to two important conclusions, one for the nature of the societal response required to address global environmental change and the other for the type of science needed to understand the Earth System. • Ethics of global stewardship and strategies for Earth System management are urgently needed. The inadvertent anthropogenic transformation of the planetary environment is, in effect, already a form of management, or rather mismanagement. It is not sustainable. Therefore, the business-as-usual way of dealing with the Earth has to be replaced – as soon as possible – by deliberate strategies of good management. • A novel system of global environmental science is emerging. The largely independent efforts of various international research programmes and numerous national projects create the basis for an Earth System science that is capable of tackling the cognitive tasks suggested by the research fi ndings above. This new science will employ innovative integration methodologies, organize itself into a global system with transnational infrastructures, and embark on a continuing dialogue with stakeholders around the world. -450 -400 -350 -300 -250 -2000 -150 -100 -50 0 50 400 350 300 250 200 150 Thousands of years atmospheric C02 (ppmV) Human perturbation 1960 1970 1980 1990 2000 360 310 320 330 340 350 b) Atmospheric CO2 Concentration (ppm) Total ozone (Dobson units) Year 1950 1960 1970 1980 1990 2000 2010 300 250 200 150 100 50 0 60 90 120 150 180 -150 -120 90 120 150 180 -150 -120 50 Generated by NCAR/ACD 2001/4/9 Binned 1.0° Lon by 1.0° Lat 60 50 0 0 -12 -10 -8 0.0020 0.0024 0.0028 1/[CO2], ppmV-1 Carbon isotope ratio, % δ 13CR=-26.9‰ δ 13CR=-24.9‰ δ 13CR=-26.3‰ δ 13CR=-22.9‰ δ 13CR=-24.1‰ δ 13CR=-25.2‰ δ 13CR=-17.8‰ δ 13CR=-19.6‰