The Earth as a System

The Earth as a System Earth’s Spheres

Earth System Science (ESS) • The study of the interactions between and among events and Earth’s spheres • A relatively new science (1988)

Earth’s Sphere • Atmosphere • Hydrosphere • Lithosphere • Biosphere • Cryosphere • Anthrosphere

Atmosphere • A gaseous sphere and it envelopes the Earth, • Consists of a mixture of gases composed primarily of nitrogen, oxygen, carbon dioxide, and water vapor.

Hydrosphere • All of the water on Earth • 71% of the earth is covered by water and only 29% is terra firma

Lithosphere • The Earth's solid surface, often called the crust of the earth. It includes continental and oceanic crust as well as the various layers of the Earth's interior.

Biosphere • All life on earth, including man, and all organisms. • The life zone on our planet distinguishes our planet from the others in the solar system.

Cryosphere • The portion of the Earth's surface where water is in a solid form • Snow or ice: includes glaciers, ice shelves, snow, icebergs, and arctic climatology

Anthrosphere • Man and his direct ancestors, hominids. • The human population, it’s buildings,dams, and other constructions.

Interconnected Spheres • Spheres are closely connected • Changes are often chain reactions • A change in one sphere results in changes in others - called an event • Forest fire destroys plants in an area • Interactions between spheres • No plants => erosion • Soil in water => increased turbidity • Turbidity => impacts water plants/animals

Event <=> Sphere • Causes & Effects • Interactions • Event <=>Sphere • Sphere<=>Sphere

ESS Analysis • Events • Cause-effect events (usually not simple) • Interactions (weblike) • Natural events • Earthquake, hurricane, forest fires • Human caused events • Oil spill, air pollution, construction

ESS Analysis • What spheres caused the event? Sphere Event • What are effects of the event on the spheres? Event Spheres • How do changes in one sphere impact on other spheres? Sphere Sphere

Understanding Interactions • Global implications • Helps people predict outcomes • Preparation for natural disasters • Environmental impacts of human activities

The Earth System behaves as a single, self-regulating system with physical, chemical, biological, and human components. The interactions and feedbacks between the component parts are complex and exhibit multi-scale temporal and spatial variability.

The understanding of the natural dynamics of the Earth System has advanced greatly in recent years and provides a sound basis for evaluating the effects and consequences of human-driven change.

2. Human activities are significantly influencing Earth's environment in many ways in addition to greenhouse gas emissions and climate change. Anthropogenic changes to Earth's land surface, oceans, coasts and atmosphere and to biological diversity, the water cycle and biogeochemical cycles are clearly identifiable beyond natural variability.

They are equal to some of the great forces of nature in their extent and impact. Many are accelerating. Global change is real and is happening now. 3. Global change cannot be understood in terms of a simple cause and effect paradigm. Human-driven changes cause multiple effects that cascade through the Earth System in complex ways.

These effects interact with each other and with local- and regional-scale changes in multidimensional patterns that are difficult to understand and even more difficult to predict. 4. Earth System dynamics are characterized by critical thresholds and abrupt changes. Human activities could inadvertently trigger such changes with severe consequences for Earth's environment and inhabitants.

The Earth System has operated in different states over the last half million years, with abrupt transitions (a decade or less) sometimes occurring between them. Human activities have the potential to switch the Earth System to alternative modes of operation that may prove irreversible and less hospitable to humans and other life.

The probability of a human-driven abrupt change in Earth's environment has yet to be quantified but is not negligible. 5. In terms of some key environmental parameters, the Earth System has moved well outside the range of the natural variability exhibited over the last half million years at least

The nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change are unprecedented. The Earth is currently operating in a no-analogue state.

The Earth as a System