may 3, 2004advanced instiute on vulnerability global change and the earth system jill jäger...

May 3, 2004 Advanced Instiute on Vulnerability

Global Change and the Earth System

Jill JägerCo-Director, Advanced Institute on

Vulnerability to Global Environmental Change



• An integrated Earth System

• Planetary machinery

• The Anthropocene Era

• The responses of the Earth System to human activities

• Consequences for human well-being

• Towards Earth System Science and Global Sustainability


An Integrated Earth System

• The extent to which, over the geologically recent past, the Earth behaves as a single, interlinked, self-regulating system was illustrated in 1999 with the publication of the 420,000 year record from the Vostok ice core

• This systematic behaviour is due to a combination of external forcing (e.g. Solar radiation) and a large and complex array of feedbacks and forcings within the Earth‘s environment


The Nature of Global Change

• Global change is more than climate change

• The world‘s population has doubled since 1960

• Since 1950 the global economy has increased by more than a factor of 15

• Economy inequality is increasing



• World petroleum consumption increased by a factor of 35 since 1960

• Transport accounts for 25% of world energy use

• Urbanisation increased 10-fold in the 20th Century

• Interconnectedness is increasing rapidly (communication, travel, globalisation of economies)



• Nearly 50% of the land surface has been transormed by direct human action

• More nitrogen is now fixed through fertilization and fossil fuel combustion than is fixed naturally

• More than half of all accessible freshwater is appropriated for human purposes

• Concentrations of greenhouse gases have increased substantially



• Coastal wetlands are significantly affected (e.g., loss of 50% of the world‘s mangrove ecosystems)

• 47 – 50% of marine fish stocks are fully exploited; 15 – 18% overexploited; 9 – 10% depleted

• Extinction rates are increasing sharply in marine and terrestrial systems


Planetary Machinery

• Without humans the Earth System functioned within domains characterised by well-defined limits and periodic patterns

• Interconnections among physical, chemical and biological processes; between land, ocean, and atmosphere

• Rapid, abrupt changes can occur


Connectivity via the oceans and their currents

• Exchange of water between surface and deep ocean

• Driven by cooling of surface water in polar regions

• Thermohaline circulation (i.e. Salinity plays a role too)

• Metaphor – a conveyor belt moving water, heat, and other properties and substances around the world‘s ocean basins


More connectivity

• Q: Why do we find carbon sink areas in the Indian Ocean?

• A: An aerosol plum from South Africa provides iron and nutrients, supporting enhanced biological activity and as a result the carbon sink in the South Indian Ocean

• Link between continental, terrestrial ecosystems and their remote (up to 5000 km) marine equivalents


The Anthropocene Era

• The planet is now dominated by human activities• Human changes are complex, interacting, often

exponential in rate, and globally significant in magnitude

• Human driving forces are also complex and interactive

• No evidence that the Earth System has previously experienced these types, scales, and rates of change („no-analogue“ situation)


Drivers of Change

• Industry

• Energy and transport

• Provision of food*

• Forestry

• Recreation and tourism


Evidence of Change

• Land cover

• Greenhouse gas concentrations, photo-oxidants, aerosols

• Hydrological cycle

• Coastal and marine environments

• Biological diversity*


Socio-economic drivers

• Urbanisation

• Globalisation*


The Response of the Earth System to Human Activities

• Human impacts do not have separate, simple cause-effect responses

• The responses cascade through the Earth System

• The responses seldom follow linear chains; they interact with each other (damping or amplifying)


A Cascade of Effects Triggered by Fossil Fuel Combustion

• Q: How can use of an air conditioner in a midwestern American home or a drive down a German Autobahn influence the ability of an African farmer in the Sahel to grow food for his family?

• Fossil fuel combustion -> production of sulphate aerosols -> changed radiative balance near Earth‘s surface -> near-surface cooling regionally


The Cascade Continues

Cooling in Europe in North America in 1960s – 1980s -> changed latitudinal temperature gradient between North Atlantic Region and tropics and subtropics -> changed atmospheric circulation -> shift position of African Monsoon over Northern Africa ->changed rainfall patterns, including drying climate in the Sahel


Multiple and Interacting Changes

• Over the last 4 or 5 decades an increasing number of stresses of human origin have begun to interact with the natural disturbance daynamics of coral reefs

• Increasing nutrient and sediment loadings (agricultural and industrial activities), intensive fishing, tourism, increasing atmospheric CO2 (changes carbonate chemistry), warming of the upper ocean layers (thermal stress -> bleaching

• Reduced resilience of reefs to external perturbations

• 58% of world‘s coral reefs at medium to high risk


Living with Global Change

• Implications for human well-being• Basic goods and services provided by the Earth

System (e.g. Food, water, air quality)• Impacts are not the same around the world• The concept of VULNERABILITY provides a

useful framework within which to study the consequences of global change

• Abrupt changes and surprises are also possible


Towards Earth System Science and Global Sustainability

• What will be the nature of changes in the Earth System over the coming decades?

• What are the implications for humankind?

• What type and scale of management responses are consistent with the scientific knowledge base?

• How must science itself change to tackle the challenges ahead?



• The Earth is a system that life itself helps to modulate

• Global change is much more than climate change. It is real, it is happening now, and it is accelerating

• The human enterprise drives multiple, interacting effects that cascade through the Earth System in complex ways

• The Earth‘s dynamics are characterised by critical thresholds and abrupt changes

• The Earth is currently in a „no-analogue“ state

may 3, 2004advanced instiute on vulnerability global change and the earth system jill jäger...

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