This is a collection of topics on Earth Systems and Global Climate Change. If you are interested to know more follow the links. I take no credit for the write up and I acknowledge contributions of persons whose work has been cited in this write up.

Delwar Ahmed

What is Earth System Science?

Earth system science views the Earth as a synergistic physical system of interrelated phenomena, governed by complex processes involving the geosphere, atmosphere, hydrosphere and. biosphere. Fundamental to the Earth system science approach is the need to emphasize relevant interactions of chemical, physical, biological and dynamical processes that extend over spatial scales from microns to the size of planetary orbits, and over time scales of milliseconds to billions of years. In building on the traditional disciplines to study the Earth, the system approach has become widely accepted as a framework from which to pose disciplinary and interdisciplinary questions in relationship to humankind. Earth system science forms the foundation of NASA’s Earth science vision as well as the basis of the NSF geoscience long range planning effort as part of the nation’s global change research objectives.

Within the concept of the Earth as a complex and dynamic entity involving the disciplinary spheres for land, air, water and life, there is no process or phenomenon that occurs in complete isolation from other elements of the system. While this system view is elegant and satisfying philosophically, the challenge to researchers and educators attempting to quantify the breadth of the system’s elements, states and processes within the classroom is enormous. No individual, academic department or university is capable of developing and offering the enormous depth and breadth of knowledge such a paradigm demands. Only by joining faculty from different disciplines within and among universities can the diversity and complexity of Earth system science be fully appreciated.

The challenge for educators to develop and offer courses in the classroom that provide this deeper understanding is demanding. Earth system science seeks to construct an overarching interdisciplinary framework of process and state of the system, and at the same time retain the strength of traditional disciplines for understanding fundamentals and complex interactions. Colleges and universities have been attracted by this holistic approach to studying the Earth and adopt Earth system science as a theme. In developing and offering introductory and advanced courses which are relevant to the broader interests of faculty and students, the challenge is to provide the necessary depth and breadth needed to serve as a foundation for advanced study among majors, and lay the foundations for sustainability and informed stewardship in striving for an Earth-aware society.

Science of Earth as a system composed of interacting subsystems. This approach emphasizes the interactive nature of the components and crosses traditional discipline boundaries. The subsystems are the atmosphere, biosphere, geosphere, and hydrosphere (following chart 9-4):

Source: http://www.strategies.org/LESSON9.html

Evolution of the Geosphere

The breakup of Gondwana over the past 160 My

For much of geological time, Antarctica formed the centre of a large land-mass called Gondwana, which also included South America, Africa, India, Australia and New Zealand. It fragmented into separate pieces over a period of 160 million years and moved apart to form the continents we know today. Geologists are uncertain as to why very large continents like Gondwana disintegrate, but the break-up processes appear to involve 'hot spots' that originate in the Earth's mantle. Antarctic rocks have still much to reveal about the mechanisms surrounding the break-up and the tectonic forces involved. This pursuit is fundamental to understanding environmental change and the evolution of life over geological time, and can be applied on a wider scale to the geology of other continents.

The Ozone Hole

Most people are aware of the Antarctic ozone hole. Its appearance during the 1980's was clear proof that the Earth functions as a complex system, and that the Antarctic is an intimately connected, component part. Man-made halocarbon gases (such as CFCs), released by the industrialized nations of the north, mix in the atmosphere, spread globally, and in the special conditions of the Antarctic spring, erode the protective stratospheric ozone layer, to the detriment of the marine and terrestrial ecosystems - and the few human beings - below.

Our atmosphere consists of nitrogen (78%) and oxygen (21%) and a small amount of other gases. Ozone (a molecule with three oxygen atoms) is quite a rare gas: even in the ozone layer there is less than one ozone molecule for every 100,000 molecules of air. Since ozone is a toxic, irritating gas, it is fortunate that its concentration at the Earth's surface is much lower than in the ozone layer. In the polluted air from large cities, ozone may be present in higher concentrations and this can cause severe health problems. In its proper place higher in the atmosphere, ozone provides a safety screen against harmful ultra-violet light from the Sun, which can cause sun burn, skin cancers and cataracts. The ozone layer also controls the temperature structure of the upper atmosphere because it can absorb radiant energy from the Sun.

Image of the Ozone Hole

The influence of the human race on climate is still a matter for study and speculation, but the ability to perturb the ozone layer is an established fact.

The discovery by the British Antarctic Survey of the Antarctic ozone hole provided an early warning of the dangerous thinning of the ozone layer worldwide, and spurred international efforts to curb the production of CFCs. If the provisions of the Montreal Protocol on Substances that Deplete the Ozone Layer of 1987 are revised, strengthened and followed, there is a reasonable prospect that the Antarctic ozone hole will permanently repair itself, but not before the next appearance of Halley's comet! (in the year 2061)

British scientists began their measurements of Antarctic ozone in 1957. The aim was to understand the important role that ozone plays through absorbing solar energy, in determining the temperature profile of the stratosphere and its wind circulation.

The amount of ozone overhead should follow a regular seasonal pattern. The Antarctic ozone layer did so for the first 20 years of BAS measurements, thereafter clear deviations were observed. In every successive spring the ozone layer was weaker than before, and by 1984 it was clear that the Antarctic stratosphere was changing progressively.

This phenomenon is the result of emissions, mainly in the northern hemisphere, of chlorofluorocarbons (CFCs) and halons. These gases are in widespread use in refrigeration, industrial solvents and fire control. If the provisions of the Montreal Protocol on Substances that Deplete the Ozone Layer of 1987 are strengthened and followed, there is a prospect that the Antarctic ozone hole will be repaired by 2100.

There are other clear connections between the Antarctic and the rest of the world. The Southern Ocean plays a key role as a major sink in the global carbon cycle, and may possibly amplify natural ice-age cycles. Beneath Antarctic sea ice and ice shelves is formed a dense, cold water that sinks into the abyss to extend under 40% of the world's oceans, with a profound effect on ocean currents and heat transport. The Antarctic ice sheet contains 90% of the world's ice and snow and would raise sea level by 60 m if it were ever to melt. The ice sheet and the surrounding sea ice and ocean are active components of the climate system through a variety of dynamic couplings and exchanges.

The Antarctic may be geographically remote, but it has great relevance to current environmental issues. Studies in the Antarctic contribute to the worldwide effort to understand how our planet works as an integrated whole, and to predict how it will behave in the future. With the Earth placed under ever greater stress as the human population and economic activities continue to grow, the research challenge is increasingly a race against time. Scientific understanding offers the only means of achieving "Sustainable Development", but the pace of change is such that policy makers need sound advice based on Earth System Science, sooner rather than later.

Climate Change

Picture of an iceberg

Antarctic studies have clarified many key issues in the science of climate change. Antarctic ice cores show that climate has always changed and reveal the clearest link between the levels of greenhouse gases in the atmosphere and surface temperatures. They show how human activity has now elevated the levels of atmospheric greenhouse gases into uncharted territory and at an unprecedented speed. The Earth's climate may respond dramatically and unexpectedly; for example, changes in the extent of sea ice and Antarctica's ice shelves may possibly disrupt the Gulf Stream.

The science of climate change involves many disciplines. BAS employs meteorologists to collect raw weather data and conduct experiments to improve the quality of weather forecasts and predictions of the future climate, while others analyze the Antarctic weather systems and the causes behind its fluctuating climate. Glaciologists study the stability of the ice sheet and the record of climate potentially extending backwards many hundreds of thousands years. Oceanographers study the highly variable Southern Ocean while biologists study the impact of changing ocean conditions on marine life. On the land biologists study the impact on organisms, already stressed by cold and desiccation, of enhanced ultra-violet radiation due to the presence of the seasonal ozone hole. And the sediments of the sea floor provide geologists with evidence of the advance and retreat of the Antarctic ice sheet as it responded to changes in climate over "geological" time.

Long-term monitoring is crucial for assessing the scale of climate change, because most changes to climate are cyclical, such as the "El-Niño". The discovery of the ozone hole and more recently the discovery of the contraction of the depth of the atmosphere relied on the careful collection and archiving of data for 30 years or more.

What is climate change: the science behind the story

http://www.climatechange.gc.ca/english/issues/what_is/index.shtml

Climate change is a change in the "average weather" that a given region experiences. Average weather includes all the features we associate with the weather such as temperature, wind patterns and precipitation. When we speak of climate change on a global scale, we are referring to changes in the climate of the Earth as a whole. The rate and magnitude of global climate changes over the long term have many implications for natural ecosystems.

A natural system known as the "greenhouse effect" regulates the temperature on earth. Human activities have the potential to disrupt the balance of this system. As human societies adopt increasingly sophisticated and mechanized lifestyles, the amounts of heat-trapping gases in the atmosphere have been increased. By increasing the amount of these gases, humankind has enhanced the warming capability of the natural greenhouse effect. It is the human-induced enhanced greenhouse effect that causes environmental concern. It has the potential to warm the planet at a rate that has never been experienced in human history.

An international scientific consensus has emerged that our world is getting warmer. Abundant data demonstrate that global climate was warmed during the past 150 years. The increase in temperature was not constant, but rather consisted of warming and cooling cycles at intervals of several decades. Nonetheless, the long term trend is one of net global warming. Corresponding with this warming, alpine glaciers have been retreating, sea levels have risen, and climatic zones are shifting.

The 1980s and 1990s are the warmest decades on record
The 10 warmest years in global meteorological history have all occurred in the past 15 years
The 20^th century has been the warmest globally in the last 600 years.

Most experts agree that average global temperatures could rise by 1 to 3.5 degrees Celsius over the next century. In Canada, this could mean an increase in annual mean temperatures in some regions of between 5 and 10 degrees.

Climate change is more than a warming trend. Increasing temperatures will lead to changes in many aspects of weather, such as wind patterns, the amount and type of precipitation, and the types and frequency of severe weather events that may be expected to occur. Such climate change could have far-reaching and/or unpredictable environmental, social and economic consequences.

Not all regions of the world will be affected equally by climate change. Low-lying and coastal areas face the risks associated with rising sea levels. Increasing temperatures will cause oceans to expand (water expands as it warms), and will melt glaciers and ice cover over land – ultimately increasing the volume of water in the world's oceans. Scientists estimate that sea levels could rise by an average of 5 cm per decade over the next 100 years. Some estimates suggest that sea levels could rise by almost a full metre by the year 2100.

Scientists have also determined that warming will be greater in polar regions than nearer to the equator, and that continental interiors will experience greater warming than coastal areas. This has serious implications for sensitive polar ecosystems, their wild species and the human inhabitants. Interior regions may face more frequent and intense heat waves.