Earth System Science
The environmental conditions of earth, including
the climate, are determined by physical, chemical, biological, and
human interactions that transform and transport materials and energy.
This is the "earth system": a highly complex entity characterized
by multiple nonlinear responses and thresholds, with linkages between
(Jickells, et al, 2005).
The Earth behaves as a system in which oceans,
atmosphere and land, and the living and non-living parts therein,
are all connected.
( Steffen et al, 2004).
The Oxford English Dictionary defines
a system as:
A set or assemblage of things connected,
associated, or interdependent, so as to form a complex unity; a whole
composed of parts in orderly arrangement according to some scheme
The earth system is composed of interacting physical, chemical, and
biological processes that move and change materials and energy on earth.
The system provides the conditions necessary for life on the planet.
For example, plants, which are part of the living system, use solar energy
to change carbon dioxide into organic carbon. Less carbon dioxide in
the atmosphere helps cool the planet. Winds and ocean currents move heat
from the tropics to higher latitudes, helping to warm the higher latitudes.
Earth systems interact through feedbacks. Positive feedbacks lead to
instability. They speed up change in the system. Negative feedbacks lead
to stability. They reduce change in the system. See feedbacks.
Until the beginning of the Anthropocene,
the systems were all natural. Now humans have begun to influence the
planet, changing the operation of many systems. Because all systems are
interconnected, a change in one systems influences all other systems.
The goal of earth system science is to obtain
a scientific understanding of the entire earth system on a global
scale by describing how its component parts and their interactions
have evolved, how they function, and how they may be expected to
continue to evolve on all timescales.
From Earth System Science Committee (1986). Overview, page 26.
Earth system science began in 1983 when the NASA Advisory Council established
the Earth System Sciences Committee, which published their revolutionary
report Earth System Science: A Program For Global
Change in 1988. The committee, chaired by Francis Bretherton,
showed for the first time how the many systems interact. The term "earth
system science" was first used by Moustafa Chahine of the NASA Jet
Propulsion Laboratory, during a meeting with Bretherton. Chahine noted
scientists had studied the solar system for many years, now it was time
to study the earth system.
A schematic diagram of the earth system proposed by the Bretherton
Organizations Studying Earth Systems
The NASA report complements work by many groups that have organized
programs to study earth. The primary international groups are:
- The World
Climate Program, established in 1980 under the World
Meteorological Organization, the International
Council for Science, and, since 1993, the Intergovernmental
Oceanographic Commission, seeks to develop the fundamental scientific
understanding of the physical climate system and climate processes
needed to determine to what extent climate can be predicted and the
extent of human influence on climate.
- The Intergovernmental Panel on Climate
Change, established in 1988 under the World
Meteorological Organization and UNEP,
seeks to assess scientific, technical and socio- economic information
relevant for the understanding of climate change, its potential impacts
and options for adaptation and mitigation.
- The International
Geosphere Biosphere Program, established in 1987 under the International
Council for Science, studies the interactions between biological,
chemical and physical processes and human systems. IGBP collaborates
with other programs to develop and impart the understanding necessary
to respond to global change.
Each of these large organizations has many sub-panels working on various
aspects of each program. Overall, tens of thousands of scientists contribute
to earth-system studies.
The remainder of this page is taken almost entirely from
the executive summaries of their reports, especially the report: Global
Change and the Earth System: A Planet Under Pressure, IGBP Science 4
- 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. Life, the carbon cycle, greenhouse gases in the atmosphere,
and earth's surface temperature are all interrelated.
- Global change is much more than climate change. It
is real, it is happening now and it is accelerating. Human activities
are significantly influencing the functioning of the earth system in
many ways; anthropogenic changes are clearly identifiable beyond natural
variability and are equal to some of the great forces of nature in
their extent and impact. The changes are so large that we are entering
a new geological age, the anthropocene.
- 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 characterized
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. Changes in the earth system can lead to abrupt
- 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.
Several developments have led to this dramatic change in our perception
- The view of earth from space, a blue-green sphere floating in blackness,
triggers emotional feelings of a home teeming with life set in a lifeless
void. It also leads us to ponder that we are alone on a spaceship with
Click on images for a zoom.
Left: Photograph of earth taken on
December 7, 1972 by the crew of Apollo 17 from a distance of about
45,000 km, while traveling to the moon. This image revolutionized
our concept of earth, and it is one of the most famous photographs
Image from NASA Earth
Right: The Blue Marble floating in
the void. earth as seen from space based on a montage of data from
three satellites. Clouds were observed on September 9, 1997 by the
Geostationary Operational Environmental Satellite (GOES) operated
by NOAA. Land color is portrayed by a vegetation index calculated
using data collected from September 9-19, 1997, by the Advanced Very
High Resolution Radiometer (AVHRR) instruments carried aboard NOAA's
Polar Orbiting Environmental Satellites. Ocean color data were collected
in late September and early October 1997 by NASA's Sea-viewing Wide
Field-of-view Sensor (SeaWiFS) satellite.
Image from NASA Visualization
Analysis Lab, Goddard Space Flight Center.
- Global observation systems and fleets of satellites allow us to study
the earth as a whole in ways that we could do before only on regional
or local scales. We can now study earth as a system.
- Global databases are now being collected and processed in a consistent
way that allows us to compare and analyze processes on a global scale
over many years.
- Dramatic advances in our ability to collect data about environmental
conditions hundreds to millions of years ago allow contemporary processes
to be viewed as continuations of past processes.
- Enhanced computing power allows us to use theory and data together
to study earth and the interactions among many different parts of the
Science has crossed the threshold of a profound shift in the perception
of the human-environment relationship, operating across humanity as a
whole and at the scale of the earth as a single system.
As earth's population increases, changes in the environment accelerate,
leading ultimately to disasters.
Wherever humans live at high population densities,
making unsustainable demands on natural systems, ... you eventually
see ecological breakdowns, unmet needs, and tensions that lead toward
conflict. Look at Darfur. Look at Rwanda. Look at Zimbabwe.
From Quammen (2005).
Earth System Science Committee (1986). Earth System Science: A Program
For Global Change. Washington DC, NASA.
Jickells, T. D., Z. S. An, et al. (2005). Global Iron Connections Between
Desert Dust, Ocean Biogeochemistry, and Climate. Science 308(5718):
Quammen, D. (2005). Tracing the Human Footprint. National Geographic.
September 2005, 208: 2--35.
Steffen, W., A. Anderson, et al. (2004). Global Change and the Earth
System: A Planet Under Pressure, Springer.
23 January, 2009