Earth System Science
One of the great scientific challenges of the 21st century is to forecast the future of planet Earth. As human activities push atmospheric carbon dioxide (CO2) and methane concentrations far beyond anything seen for nearly half a million years (prompting the strongest statement yet from the Intergovernmental Panel on Climate Change that human activities are warming the world), we find ourselves, literally, in uncharted territory, performing an uncontrolled experiment with planet Earth that is terrifying in its scale and complexity.
Wrestling to understand these challenges is the young, and still emerging, discipline of Earth System Science (ESS). Polar-ice and ocean-sediment cores (the Vostok ice core from Antarctica, for example) provide a picture of the last half-million years of Earth's history unimaginable even two decades ago, and mark the emergence of ESS as the discipline that deals with our planet as a complex, interacting system. ESS takes the main components of planet Earth--the atmosphere, oceans, freshwater, rocks, soils, and biosphere--and seeks to understand major patterns and processes in their dynamics. To do this, we need to study not only the processes that go on within each component (traditionally the realms of oceanography, atmospheric physics, and ecology, to name but three), but also interactions between these components. It is the need to study and understand these between-component interactions that defines ESS as a discipline in its own right.
Physicists have long understood the "Goldilocks effect"--why, in general terms, Earth's natural blanket of atmospheric CO2 and distance from the Sun make the planet "just right" for life, neither too hot (like Venus) nor too cold (like Mars). James Lovelock's penetrating insights that a planet with abundant life will have an atmosphere shifted into extreme thermodynamic disequilibrium, and that Earth is habitable because of complex linkages and feedbacks between the atmosphere, oceans, land, and biosphere, were major stepping-stones in the emergence of this new science. We still do not understand all these feedbacks and cannot, yet, build a model that reproduces changes in Earth's temperature and atmospheric composition revealed by the Vostok ice core, but these problems now hold center stage in ESS.
There are also numerous other interrelated challenges for this emerging discipline. Do species' identities matter in biosphere-geosphere interactions, or is life simply "green slime"? What are the main feedbacks influencing planetary inorganic-organic carbon dynamics? How does human domination of the global nitrogen cycle, or rapid urbanization, impact on other components of the Earth system? How do we link models of geophysical processes to those describing human socioeconomic activities? The time scales involved in such questions range from hundreds to hundreds of millions of years, and involve processes that are highly nonlinear, presenting considerable challenges for modelers.
The greatest challenge for the new discipline, however, is to provide prescriptions that will reverse current human abuse of planet Earth, signposting routes to a sustainable future. The biggest barriers to rapid progress are institutional. Comparisons between ESS and medical science are telling. Scientists and engineers from many disciplines routinely work together within institutions and organizations to improve human health. We would be startled if it were not so. The health of the planet is a different story. Although a few pioneering individuals and institutions around the world recognize the need for the strong interdisciplinary work that defines ESS, in the main we lack the organizations to nurture this new discipline. There are, as far as I am aware, no undergraduate degree courses in ESS. A mere handful of U.S. and European institutions (including Penn State, the University of California at Irvine, the University of Maryland, the Danish Centre for Earth System Science, the Potsdam Insitute, and ETH in Zurich) offer graduate programs and the kind of interdisciplinary working environments that are essential for the rapid development of ESS. The International Geosphere-Biosphere Programme (IGBP) serves as a pioneering focus for ESS, but lacks the resources to do more. Funding agencies, compartmentalized into traditional disciplines, are ill-equipped to rise to the new challenges posed by ESS.
It is hard to imagine a more important discipline than Earth System Science. We urgently need to overhaul our thinking and rejig our institutions to allow this crucial new science to flourish.
What is a system?
Systems science is the interdisciplinary field of science, which studies the nature of complex systems in nature, society, and science. It aims to develop interdisciplinary foundations, which are applicable in a variety of areas, such as engineering, biology, medicine and social sciences.
A system is defined as a collection of interacting objects. The Earth and its atmosphere defines the Earth system. A system consists of three basic elements: (1) a functioning set of components, (2) a flow of energy which powers them, and (3) a process for the internal regulation of their functioning called feedback
Earth as a System
Earth is a complex, evolving body characterized by ceaseless change. To understand Earth on a global scale means using a scientific approach to consider how Earth's component parts and their interactions have evolved, how they function, and how they may be expected to further evolve over time. This visualization adapted from NASA helps explain why understanding Earth as an integrated system of components and processes is essential to science education.
Understanding our planet as an integrated system of components and processes is a fundamental part of Earth and space science research. Just as the human body is composed of interrelated systems that control specific bodily functions, Earth's four principal components — the atmosphere (air), lithosphere (land), hydrosphere (water), and biosphere (life) — perform critical roles that, together, support and sustain life on the planet.
Nothing influences the subsystems that contribute to Earth's dynamic behavior more than heat. Heat comes from two sources: solar energy and radioactivity in the Earth's core. Because of the angle at which the Sun strikes Earth, Earth's surface is heated unevenly. This creates Earth's three major climate zones — tropical, temperate, and polar — which then influence what types of life flourish in different locations.
The uneven heating also controls weather systems. The heat absorbed by the oceans and carried by its currents is constantly being released into the atmosphere. This heat and moisture drive atmospheric circulation and set weather patterns in motion. The weather patterns then influence vegetation, as well as erosion and sediment transport.
The other heat source, deep within Earth's core, is responsible for plate tectonics, which gives the Earth its physical character: mountain ranges and valleys, ocean basins and lake beds, and islands and trenches. The heat from Earth's core generates convection cells within its mantle, which help drive plate activity.
Ever since the first photos were sent back from space, our view of Earth has changed. Remote sensing instruments, such as satellites, allow us to better understand the interrelationships between the different subsystems. For instance, recordings made by remote and Earth-based instruments show that significant surface warming has occurred over the past three decades. Knowing this, scientists are working to determine how this will affect — and already is affecting — the entire Earth system.
Environmental Problems
A variety of environmental problems now affect our entire world. As globalization continues and the earth's natural processes transform local problems into international issues, few societies are being left untouched by major environmental problems.
Some of the largest problems now affecting the world are:
Acid Rain
The term acid rain refers to what scientists call acid deposition. It is caused by airborne acidic pollutants and has highly destructive results.
Scientists first discovered acid rain in 1852, when the English chemist Robert Agnus invented the term. From then until now, acid rain has been an issue of intense debate among scientists and policy makers.
Acid rain, one of the most important environmental problems of all, cannot be seen. The invisible gases that cause acid rain usually come from automobiles or coal-burning power plants.
Acid rain moves easily, affecting locations far beyond those that let out the pollution. As a result, this global pollution issue causes great debates between countries that fight over polluting each other's environments.
For years, science studied the true causes of acid rain. Some scientists concluded that human production was primarily responsible, while others cited natural causes as well. Recently, more intensive research has been done so that countries have the information they need to prevent acid rain and its dangerous effects.
The levels of acid rain vary from region to region. In Third World nations without pollution restrictions, acid rain tends to be very high. In Eastern Europe, China, and the Soviet Union, acid rain levels have also risen greatly. However, because acid rain can move about so easily, the problem is definitely a global one.
Air Pollution
Every day, the average person inhales about 20,000 liters of air. Every time we breathe, we risk inhaling dangerous chemicals that have found their way into the air.
Air pollution includes all contaminants found in the atmosphere. These dangerous substances can be either in the form of gases or particles.
Air pollution can be found both outdoors and indoors. Pollutants can be trapped inside buildings, causing indoor pollution that lasts for a long time.
The sources of air pollution are both natural and human-based. As one might expect, humans have been producing increasing amounts of pollution as time has progressed, and they now account for the majority of pollutants released into the air.
Air pollution has been a problem throughout history. Even in Ancient Rome people complained about smoke put into the atmosphere.
The effects of air pollution are diverse and numerous. Air pollution can have serious consequences for the health of human beings, and also severely affects natural ecosystems.
Because it is located in the atmosphere, air pollution is able to travel easily. As a result, air pollution is a global problem and has been the subject of global cooperation and conflict.
Some areas now suffer more than others from air pollution. Cities with large numbers of automobiles or those that use great quantities of coal often suffer most severely from problems of air pollution.
Global Warming
On June 23, 1988, James Hansen, the director of the Goddard Institute at NASA, told the Senate Committee on Energy and Natural Resources that global warming was a reality and that is was extremely dangerous.
Global warming, also known as the greenhouse effect, immediately received international attention. Scientists, environmentalists, and governments around the world took an interest in the subject.
Global warming is called the greenhouse effect because the gases that are gathering above the earth make the planet comparable to a greenhouse. By trapping heat near the surface of the earth, the greenhouse effect is warming the planet and threatening the environment.
Many scientists criticized Mr. Hansen's report, and the debate over global warming continues today.
Current fears stem largely from the fact that global warming is occurring at such a rapid pace. Models are predicting that over the next century, the global temperature will rise by several degrees.
Some scientists still do not think that the effects of global warming are as severe as some people say. They think that droughts, hurricanes, and floods often blamed on global warming might actually have other causes.
One major difficulty in studying global warming is the fact that weather data only exists for the last century and a half. As a result, understanding the present and predicting the future are very difficult.
Hazardous Waste
In addition to releasing gases and particles into the atmosphere, humans produce waste that is dumped on the environment. Often, this waste is hazardous and dangerous to both nature and human life.
The levels of dangerous wastes continue to grow. Industries and individuals continue to be largely unaware of this major environmental problem.
As a result, many people and industries are failing to prevent the creation of hazardous waste or to limit the negative effects it produces.
Individuals often throw out goods without realizing that they are headed for a landfill and could be dangerous for the environment. No matter where people put these hazardous waste materials, there is always a chance that they could find their way into the ground, and eventually into our bodies.
Corporations usually want to avoid the costs associated with having to limit creation of hazardous waste. Consequently, they build landfills on site and fill them with waste, or sometimes pay to have their waste removed. Often, hazardous materials are transported to areas that accept money to take the waste.
It may prove very difficult to reduce hazardous waste in the future. Unlike many other environmental problems, waste creation is something people do not often think about.
In the future, people may have to reduce not only their generation of hazardous waste, but also their consumption of many products that end up in landfills.
Ozone Depletion
The ozone layer protects the Earth from the ultraviolet rays sent down by the sun. If the ozone layer is depleted by human action, the effects on the planet could be catastrophic.
Ozone is present in the stratosphere. The stratosphere reaches 30 miles above the Earth, and at the very top it contains ozone. The suns rays are absorbed by the ozone in the stratosphere and thus do not reach the Earth.
Ozone is a bluish gas that is formed by three atoms of oxygen. The form of oxygen that humans breathe in consists of two oxygen atoms, O2. When found on the surface of the planet, ozone is considered a dangerous pollutant and is one substance responsible for producing the greenhouse effect.
The highest regions of the stratosphere contain about 90% of all ozone.
In recent years, the ozone layer has been the subject of much discussion. And rightly so, because the ozone layer protects both plant and animal life on the planet.
The fact that the ozone layer was being depleted was discovered in the mid-1980s. The main cause of this is the release of CFCs, chlorofluorocarbons.
Antarctica was an early victim of ozone destruction. A massive hole in the ozone layer right above Antarctica now threatens not only that continent, but many others that could be the victims of Antarctica's melting icecaps. In the future, the ozone problem will have to be solved so that the protective layer can be conserved.
Smog
In many areas around the word, smog has reached extraordinary levels. Some governments have quickly reacted with severe measures in response to the problem.
The word smog is a combination of the words smoke and fog. The term was invented by a Glasgow public health official, Des Voeux.
Smog causes a smoky dark atmosphere to arise over cities. It decreases visibility, and creates a haze throughout the area.
Numerous studies have monitored smog throughout the world. Some of the world's dirtiest cities have millions of inhabitants, all of whom are threatened by the smog.
Modern Los Angeles suffers severely from smog, as London did in the 19th century. These two areas released certain chemicals into the air and created a foggy atmosphere. In London, where fog levels have now fallen far below those of years ago, people were often unable to see their hands and sometimes could not walk around.
It took a long time for governments to act to control smog. The Clean Air Act of 1970 in the United States limited legal smog levels. The Environmental Protection Agency now measures levels of smog and regulates smog producers.
Despite government action to reduce them, smog levels remain very high in many cities. Even those areas that do successfully reduce smog may be the victims of smog blown in from other locations.
Water Pollution
Attention for water pollution exploded in the 1980s. The oil spill of the Exxon Valdez showed many around the world just how horrible the effects of water pollution could be.
However, even the Exxon Valdez spill barely touched the surface of the problem of water pollution. The ship spilt only 5% of the oil spilt that year, and oil is just one of many pollutants that people dump into the water every year.
Every year, 14 billions pounds of sewage, sludge, and garbage are dumped into the world's oceans. 19 trillion gallons of waste also enter the water annually.
The problem of ocean pollution affects every nation around the world. This is especially true because water is able to transport pollution from one location to another.
For many years, chemicals were dumped into bodies of water without concern. While many countries have now banned such behavior, it continues to go on today.
As the world has industrialized and its population has grown, the problem of water pollution has intensified. The simple fact that millions of people live along coastlines and near rivers means that these bodies of water are likely candidates for heavy and destructive pollution.
It is hard to know now what our oceans will look like in the future. Just how damaged they will be by pollution is uncertain.
Overpopulation
The world's population has been booming for years. The population is now threatening to reach the stage where there are simply too many people for the planet to support.
Around 1850, the world population reached one billion. By 1987, it was at five billion and still rising rapidly.
Third World nations are responsible for a great deal of the population growth. In 1989, about 90% of the people being born were in developing countries. The populations of Third World countries are expected to continue to boom.
The United Nations Population Fund predicts that by the middle of the next century, the world's population will stabilize at about 14 million people. If fertility rates were decreased to 2.1 births per woman, population stabilization could be achieved sooner.
In 1968, Paul Ehrlich published The Population Bomb. The book described how the world population had risen, citing the discovery of agriculture as the cause. The book predicted that population growth would result in widespread famine and even nuclear war. While some of his predictions turned out to be false, famine did occur at high levels in later years.
Overpopulation has been disastrous for the planet. Greater populations have polluted and consumed more, ruining the environment and creating or intensifying a variety of problems. Also, with the food supply limited, increases in population make shortages in many parts of the world even worse.
Rain Forest Destruction
The atmosphere and oceans are not the only parts of the environment being damaged. Rain forests are being quickly destroyed as well, and their survival is questionable.
E.O. Wilson, a biologist at Harvard, called the depletion of rain forest areas "the greatest extinction since the end of the age of dinosaurs."
Unlike some environmental issues, rain forest depletion has fortunately received significant public and media attention.
Despite the opposition to the cutting down of rain forests, the problem continues. Every year, Brazil chops down an area of forest the size of the state of Nebraska.
In addition to the Amazon's rain forests, many other forests are being cut down as well. In Indonesia, Zaire, Papua-New Guinea, Malaysia, Burma, the Philippines, Peru, Colombia, Bolivia, and Venezuela, rain forests that were once great have been lost.
According to some estimates, 50 million acres of rain forest are cut down every year. The United Nations says the figure is closer to 17 million acres. The World Wildlife Fund says that every minute, 25 to 50 acres are cut or burned to the ground.
The world's growing population has been a primary cause of rain forest destruction. More people need land to live on and wood products to consume. Limiting population growth may be the first in a series of steps that would limit the destruction of the rain forests.
