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Fabrics in an era of global warming

May 1st, 2008 / By: / Case Studies

A look at our changing climate.

For millennia, growth in population and knowledge advanced slowly. Suddenly, in the early 19th century, population zoomed upward crossing the billion mark, and is now climbing above six billion (fig. 1.) By the end of the current century, it is expected that the world’s population will grow to 10 billion. Another development started in the late 17th century, with advancements in science and technology that set off an unprecedented industrial revolution led by the discovery of 97 new elements in a period of 250 years (fig. 2.) The confluence of these two events resulted in a major expansion in the need for energy production.

Before 1800, wood was the principal source of energy in the world. In fact, 95% of the world’s fuel was supplied by this source, with the remaining 5% being supplied by the muscle of man and beast. With the advent of the industrial age, the fossil fuels—coal, oil and natural gas—became the world’s principal energy sources. As a byproduct of the combustion process, the production of energy using fossil fuels releases carbon dioxide (CO2) into the atmosphere. In the past, the carbon dioxide that is organically produced from human and animal waste could be absorbed by plants and the world’s oceans, following nature’s carbon cycle. Photosynthesis converts CO2 and water that is soaked up by plants into carbohydrates and oxygen, by using solar radiation that is absorbed by the plants’ chlorophyll. The world’s oceans act as a sink for CO2 through the process of solubility, consequently increasing the acidity of seawater.

Starting before the turn of the 20th century, the enormous quantities of carbon dioxide discharged by our machines began to overwhelm nature’s cycle and fled to the troposphere and stratosphere (fig.3.) There, these gases, (CO2 as well as methane, nitrous oxide and others) enveloped our planet and, as in a greenhouse, permitted light to enter but prevented heat energy from exiting the troposphere. This resulted in what we know as global warming, causing a steady increase in the world’s average temperature.

The problem

For the past thousand years, the average temperature in the world has been relatively constant, though it had very slowly crept downward until the end of the 19th century (fig. 4.) Since then, there has been a sudden, sharp, and continuing rise in temperature of 0.7°C. This is a seemingly small number when compared to seasonal temperature variations, but is startling when measure against the 5°C rise that took place since the end of the last ice age about 10,000 years ago.

During this same millennium, the earth passed through the Medieval Warm Period that endured between the 10th and 14th centuries, when temperatures were about 1°C warmer than now. In contrast to this warm period, the earth passed through the Little Ice Age between the 15th and 19th centuries, when the average temperature was between one and two degrees cooler than today.

Such warming and cooling periods have occurred naturally throughout the earth’s history. Centuries-long cold spells such as happened during the Little Ice Age seem to recur every 1,400 to 1,600 years. These are then followed by centuries-long warming periods. This recurring cyclical variation in temperature has been cited by some as a reason for the increase in the world’s temperature in the 20th century. However, the suddenness of the present rise, coupled with increasing industrialization and a simultaneous increase in atmospheric carbon dioxide, suggests another cause.

The human imprint on climate

Carbon dioxide is always present in the atmosphere. It is the food for all plant life and is, apart from water vapor, the principal greenhouse gas that occurs naturally and allows our planet to be habitable. Of course, the most common greenhouse gas is water vapor, which increases with increasing temperature. Like the glass roof of a greenhouse, these gases form an insulating blanket in the upper atmosphere, trapping heat by re-radiating heat energy back to Earth’s surface. Without it, the planet would be a cold, inhospitable place with an average temperature of -32°C rather than the 16°C that nurtures us. How delicate is the balance that permits life on Earth? If 25% less radiation were to reach the Earth, its temperature would be lower than 0°C. With 25% more radiation, Earth’s temperature would be higher than 30°C. Either of these conditions would be intolerable. Animals breathe in oxygen-rich air and breathe out carbon dioxide that is then absorbed by plants, which are irradiated by the sun and, through the process of photosynthesis, release oxygen back into the atmosphere. In the fall and winter, the process reverses as plants decay, releasing carbon dioxide. The world’s oceans cooperate by absorbing about one third of human-generated carbon dioxide. It is a grand scheme of global recycling (fig. 5.)

In the winter, the atmosphere holds more carbon dioxide than in summer, as if the earth itself breathes once a year. This cyclic event has taken place for hundreds of thousands of years while the average level of carbon dioxide remained relatively constant…at least until the beginning of the 20th century. Since then, the atmospheric carbon dioxide levels have risen steadily from about 290ppm to over 380ppm, a 31% increase, which is substantially greater than in any previous interglacial period and double the concentration in any ice age (as confirmed by analyzing and dating gases trapped deep in Antarctic ice.) Dr. Charles D. Keeling was the first to measure carbon dioxide in the atmosphere. Starting in 1955 he would camp out at Big Sur in California, collecting air samples to measure the concentration of carbon dioxide. He had been recruited for this study by Roger Revelle, the director of the Scripps Institution of Oceanography, who had been one of the first scientists to suspect that carbon dioxide was responsible for the earth’s warming. Over the years, Dr. Keeling plotted his results on what is now called the Keeling Curve, demonstrating the upward trend of carbon dioxide concentration (fig. 6.)

Currently, the United States alone pumps 5.5 billion tons of carbon dioxide into the atmosphere each year. It would take a forest the size of Jupiter to absorb that much carbon dioxide. Even the world’s oceans can’t help, because their ability to absorb carbon dioxide diminishes exponentially as more is absorbed. Consequently, as much as 40% of it stays in the atmosphere and will reside there for centuries.

In the next 50 years the world’s energy use is expected to double, led by the rapidly increased industrial development of China and India. China alone will burn enough coal, releasing sulfur dioxide and carbon dioxide as well as other noxious gases, to exceed by 500% the emissions levels sought by the Kyoto Protocol.* This results from the fact that a new coal-fired power plant is completed every 7–10 days to fulfill the need for a growing industrial economy but without the necessary equipment to remove pollutants from smokestacks. The resulting polluting clouds that head east cause acid rain, which is already affecting Japan and has even reached the west coast of the United States. It is estimated that by 2025, China alone will release twice as much carbon dioxide into the atmosphere as the United States. India, with a population that is expected to exceed China’s by 2030, is right behind China in adding to the problem.

To this day, the concentration of carbon dioxide in the atmosphere continues to increase, and within a relatively short time, the continued use of fossil fuels will outstrip precious planetary resources and further intensify the global warming problem.

To further exacerbate the global warming, there are other greenhouse gases that are attributable to human activity including methane (from two billion farting and belching cows, sheep and goats, as well as from rice paddies and sewage), a gas that is over 20 times more effective than carbon dioxide in trapping heat; nitrous oxide (from fertilizers), a gas that is 310 times more effective in trapping heat; and industrial fluorocarbons such as CFC refrigerants and aerosols that, in addition to being highly effective in trapping heat, can linger in the atmosphere for as long as 50,000 years. However, carbon dioxide from the burning of fossil fuels remains the primary cause for unbalancing the global climate system.

How much longer can the planet deal with such enormous changes without rebelling?

The human imprint on current and future climate is incontrovertible and, as a panel of international climate experts agreed in 2001, “Most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentration.” We have managed to make our presence felt on Earth—but to our future detriment. Lonnie Thompson, an Ohio State paleoclimatologist, has called this “a remarkable uncontrolled experiment.” Even if we had stabilized emissions of greenhouse gases by the year 2000, the concentrations of carbon dioxide in the atmosphere are expected to have doubled from the pre-industrial level by the year 2100. By then, the resulting average temperature in the world will increase by about 3°C. (Without greenhouse gases, the earth’s global temperature would actually have fallen during the 20th and into the 21st centuries.) The earth has not experienced this level of warming since the Climatic Optimum Period, from 7,000 to 3,000 years ago.

Possible solutions

There is no longer a question about whether we have entered into an era of warming temperatures, changes in precipitation patterns and the other many dire consequences of our continued use of fossil fuels. Following the latest summary report from the IPCC (Intergovernmental Panel on Climate Change), our attention must now be focused on finding ways to solve the seemingly hopeless problems caused by inefficient uses of energy, lack of efforts toward conservation and lack of direction toward sustainability.

Most efforts to date have been directed at finding ways to reduce the amount of carbon dioxide released into the atmosphere from power generation, transportation vehicles and industrial production. Increasingly, we look to the sun to provide carbon free energy and here is where it makes sense to look at the contribution that fabric structures can make. Translucent fabric structures provide a free source of daylight lighting reducing the need for energy using artificial lighting. Fabrics also provide protection from rain and can even be used as collection devices to capture water, a shrinking resource. Solar cells embedded in a fabric structure can serve both as a building enclosure and as a source of energy. Fabric used to encapsulate farm waste as part of an enclosure to generate methane for power can provide a neutral energy balance to the world’s farms. As a part of a solar chimney (as proposed by J. Schlaich), a fabric canopy can capture heat that is vented up a chimney fitted with a wind generator to create electric power. Undoubtedly there are many other ways limited only by the inventiveness of people, in which fabrics can be used to help reverse the effects of global warming.

Matthys Levy is a founding principal and chairman emeritus of Weidlinger Associates, consulting engineers. He is the recipient of many awards, including the ASCE Innovation in Civil Engineering Award and the IASS Tsuboi Award. He has published numerous papers in the field of structures, computer analysis, aesthetics and building systems design, and is the co-author of Why Buildings Fall Down and several other books on structure and engineering.
*The Kyoto Protocol, established in 1997, came into force in 2005 with ratification by 141 countries. It establishes emission targets for each country with the objective of reducing emissions by 5.2% by 2012. The United States has not ratified the agreement, saying that it would prove too costly.

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