ENVIRONMENTAL SCIENCE

ENVIRONMENTAL SCIENCE
14th Edition A Study of Interrelationships

Chapter Outline 17.1 Earth Is a Greenhouse Planet
17.2 Geologic Evidence of Climate Change 17.3 Growth in Knowledge of Global Warming and Climate Change

Chapter Outline 17.4 Sources and Impacts of Principal Greenhouse Gases
17.5 The Current State of Knowledge about Climate Change 17.6 Consequences of Climate Change 17.7 Addressing Climate Change

17.1 Earth Is a Greenhouse Planet
The Earth is unique among the planets in having a temperature that allows for water to exist in a liquid form. All living things are primarily made up of water. The human body is over 50 percent water. All early forms of life developed in the oceans. The presence of liquid water is essential for life as we know it.

The Earth’s temperature is determined by several factors: Earth’s distance from the sun Changes in the energy output of the sun The presence of carbon dioxide in the atmosphere. Although Earth’s orbit around the sun results in small changes in the distance between the Earth and sun and the sun’s energy changes slightly on about an 11 year cycle, these differences appear to have little effect on Earth’s temperature.

Several gases in the atmosphere are transparent to ultraviolet and visible light but absorb infrared radiation. These gases allow sunlight to penetrate the atmosphere and be absorbed by the Earth’s surface. This sunlight energy is reradiated as infrared radiation (heat), which is absorbed by the greenhouse gases in the atmosphere. Because the effect is similar to what happens in a greenhouse, these gases are called greenhouse gases, and the warming that occurs because of their presence is called the greenhouse effect

Greenhouse Effect

Carbon dioxide is a greenhouse gas. Although the amount of carbon dioxide in the atmosphere is small, its effect is significant. According to NASA if there were no carbon dioxide in the atmosphere Earth’s temperature would be about -18oC (0oF) instead of the current temperature of about 15oC (60oF). Thus the greenhouse effect caused by the presence of carbon dioxide in the atmosphere makes Earth suitable for life.

17.2 Geologic Evidence of Climate Change
Although the phrases global warming and climate change are sometimes used interchangeably, they are really different aspects of the same problem. Global warming relates to an average increase in temperature of the Earth’s atmosphere Climate change refers to the many other changes that come about because of global warming.

17.2 Geologic Evidence of Climate Change
Geologic studies of Earth’s history gave clues that climate had changed significantly over time. Some geologic periods were hotter than today and some were colder. Evidence of continental glaciers that covered large portions of North America, Europe, and Asia brought about a recognition that climate change had happened in the recent geologic past.

Continental Glaciers

17.3 Growth in Knowledge of Global Warming and Climate Change
The average temperature of the Earth has been increasing since1980s. Scientists initially tried to determine if the warming was a natural phenomenon or the result of human activity. Evidence of past climate change going back as far as 160,000 years indicates a close correlation between the concentration of greenhouse gases in the atmosphere and global temperatures.

Changes in Average Global Temperature

Computer models are not the only evidence of the causes and effects of climate change: Records of the amount of carbon dioxide in the atmosphere that show steady increase in the amount of carbon dioxide Studies of gas bubbles trapped in glaciers that indicate what the atmosphere was like before the time of the industrial revolution that began in the mid1700s Satellite photos that show how snow and ice conditions change Migration behavior of terrestrial and marine animals that show changes in the time of migration or the route followed Ocean studies of CO2 content, pH change, and other changes in chemistry

Evidence of climate change (continued): Changes in growing seasons Physical measurements of the retreat of glaciers and thickness of ice sheets Effects of increased carbon dioxide on photosynthesis Wind patterns Ocean currents Effects of particulates from natural (wind erosion, volcanos) and human activities on climate Sea level measurements Frequency and strength of tropical storms

Research Related to Climate Change

17.4 Sources and Impacts of Principal Greenhouse Gases
The most important greenhouse gases are: Carbon dioxide (CO2), Methane (CH4) Chlorofluorocarbons (primarily CCl3F and CCl2F2) Nitrous oxide (N2O).

Carbon dioxide (CO2) is the most abundant of the greenhouse gases and is responsible for about 64 percent of global warming. It occurs as a natural consequence of respiration and fermentation by organisms. However, much larger quantities are put into the atmosphere as a waste product of energy production. Another factor contributing to the increase in the concentration of carbon dioxide in the atmosphere is deforestation.

Measurement of carbon dioxide levels at the Mauna Loa Observatory in Hawaii shows that the carbon dioxide level increased from about 316 parts per million (ppm) in 1958 to about 394 ppm in 2013. This is an increase of about 25 percent. It is generally accepted that the amount of carbon dioxide in the atmosphere prior to the industrial revolution was about 280 ppm. The current concentration represents an increase of 40 percent over preindustrial concentrations.

Changes in Atmospheric Carbon Dioxide

Methane (CH4) is the second most abundant greenhouse gas and is responsible for about 18 percent of global warming. It comes from biological sources and as a byproduct of fossil-fuel use. Several kinds of microorganisms that are particularly abundant in wetlands and rice paddies release methane into the atmosphere. Natural gas is primarily methane and oil and coal, contain some methane as well. Currently the amount of methane in the atmosphere continues to grow. Preindustrial concentrations were about 700 parts per billion (ppb). Current concentrations are about 1800 ppb.

Changes is Atmospheric Methane

Nitrous oxide (N2O), a minor component of the greenhouse gas picture, enters the atmosphere primarily through the use of fertilizers and fossil fuels. Nitrogen-containing fertilizers and animal manure used to improve agricultural production contain nitrogen compounds. Certain soil bacteria convert these compounds to nitrous oxide.

Chlorofluorocarbons (CFCs) are also a minor component of the greenhouse gas picture and are synthetic compounds produced for particular uses. There are no natural sources of CFCs. CFCs were widely used as refrigerant gases in refrigerators and air conditioners, as cleaning solvents, as propellants in aerosol containers, and as expanders in foam products.

Although they are present in the atmosphere in minute quantities, they are extremely efficient as greenhouse gases (about 15,000 times more efficient at retarding heat loss than is carbon dioxide). Because chlorofluorocarbons are a major cause of ozone destruction, production and use of chlorofluorocarbons has been sharply reduced and scheduled to be eliminated by 2020.

17.5 The Current State of Knowledge about Climate Change
In 1988, the United Nations Environment Programme and the World Meteorological Organization established the Intergovernmental Panel on Climate Change (IPCC) to study the issue and make recommendations. A main activity of the IPCC is to provide an assessment of the state of knowledge about climate change at regular intervals.

The IPCC is organized into several working groups: Working Group I deals with the physical science that relates to climate change. Working Group II deals with the impacts of climate change. Working Group III deals with how to mitigate the effects of climate change.

Working Group I published its portion of the Fifth Assessment Report, Climate Change 2013: The Physical Science Basis, in September of 2013. Two hundred and fifty-nine scientists from around the world were involved in writing portions of the report. Over 600 people contributed material for the report.

Their report restated several important conclusions from previous reports and added several new observations: Human activity is clearly influencing climate. Increased concentrations of greenhouse gases, particularly carbon dioxide, are causing an increase in temperature. Evidence of increased temperature is clear.

Fifth Assessment Report findings (continued): Evidence of increased temperature is clear. The average temperature of the Earth has increased °C ( °F) since 1880. Amounts of spring snow and ice have decreased in the northern hemisphere. Snow is melting earlier in the year. The number of cold days has decreased and the number of warm days has increased. The arctic region is warming more than the rest of the world. Permafrost (permanently frozen soil) temperatures have increased 2 to 3oC ( oF) and the thickness of the permafrost layer and the area of the world that has a permafrost layer have decreased.

Fifth Assessment Report findings (continued): There has been a reduction in the area covered by arctic sea ice at the end of the summer season (September). Greenland and Antarctic ice sheets have been losing mass Glaciers are melting The arrival of spring is earlier in many parts of the world.

Fifth Assessment Report findings (continued): Increased carbon dioxide in the atmosphere and increased temperature are affecting oceans. About 28 percent of carbon dioxide emissions end up in the ocean. Increased CO2 dissolved in water has decreased pH by 0.1pH unit. (A 26 percent increase in hydrogen ion concentration.) About 90 percent of the additional energy added to the Earth has been stored in the oceans resulting in an increase of about 0.44oC (0.8oF) in the temperature of the upper 75 meters of the oceans in the last 40 years. Sea level has risen about 19 cm (7.5 in.) between 1901 and 2010. The rate of sea level rise has been increasing and was about 3.2mm/year (0.125 inches/year) from 1993 to 2010.

17.6 Consequences of Climate Change
A small increase in the average temperature of the Earth may seem trivial, however, such an increase could set in motion changes that could significantly alter the climate of major regions of the world. Computer models suggest that rising temperature will lead to changes to the hydrologic cycle, sea level, human health, the survival and distribution of organisms, and the use of natural resources by people. Furthermore, some natural ecosystems or human settlements will be able to withstand or adapt to the changes, while others will not.

17.6 Consequences of Climate Change
Poorer nations are generally more vulnerable to the consequences of global warming. These nations tend to be more dependent on economic activity that is climate-sensitive, such as subsistence agriculture, and lack the economic resources to adjust to the changes that global warming may bring. The Intergovernmental Panel on Climate Change has identified Africa as “the continent most vulnerable to the impacts of projected changes because widespread poverty limits adaptation capabilities.”

Disruption of the Hydrologic Cycle
In a fundamental way the hydrologic cycle (evaporation, precipitation, water flow, groundwater, etc.) is driven by energy. The primary source of energy is the temperature of the Earth, which is determined by the input of energy from the sun and the heat-trapping effect of greenhouse gases. Thus, a change in the Earth’s temperature is expected to change weather and climate.

Weather includes short-term activities such as; temperature changes, rain and snow events, winds, clouds, and other factors. Climate is the long term average of weather patterns. Thus, if climate is changing we should expect changes in weather patterns also.

Higher temperatures result in increased evaporation, which will cause some areas to become drier, while the increased moisture in the atmosphere will result in greater rainfall in other areas. Snowfall patterns are also expected to change with some areas receiving more snow and others less.

Recent data suggest that: The amount of spring snow has decreased Snow is melting earlier in the year Hurricanes are more powerful There are more hot days and fewer cold days Spring is arriving earlier

Rising Sea Level A warmer Earth will result in rising sea levels for two different reasons: When water increases in temperature, it expands and takes up more space. In addition, higher temperatures are causing the melting of glaciers, which adds more water to the oceans. Rising sea level erodes beaches and coastal wetland, inundates low-lying areas, and increases the vulnerability of coastal areas to flooding from storm surges and intense rainfall.

Flooding from Hurricane Sandy

Rising Sea Level By 2100, the IPCC projects sea level to rise by 26 to 98 centimeters (10-39 inches). A 50-centimeter (20-inch) sea-level rise will result in substantial loss of coastal land in North America, especially along the southern Atlantic and Gulf coasts, which are subsiding and are particularly vulnerable. Many coastal cities would be significantly affected by an increase in sea level. World-wide about 600 million people live in low-lying coastal areas. The land area of some island nations and countries such as Bangladesh would change dramatically as flooding occurred.

Health Effects The most direct effect of climate change is the impact of hotter temperatures. Extremely hot temperatures increase the number of people who die (of various causes) on a given day. For example, people with heart problems are vulnerable because the cardiovascular system must work harder to keep the body cool during hot weather.

Heat Affects Health In 2010, a record-breaking heat wave in Russia resulted in 62 consecutive days of above normal temperatures, and in Moscow. About 11,000 deaths were attributed to the heat. In June 2013, a heat wave in the U.S. Southwest resulted in several record temperatures and several deaths. Even though the temperatures in the U.S. Southwest were higher than those in Russia, the number of U.S. deaths was much lower because most U.S. buildings have air conditioning and most Russian buildings do not.

Heat Affects Air Pollution
Climate change will also make air pollution problems worse. Higher air temperature increases the concentration of ozone at ground level, which leads to injury of lung tissue and increases the incidence of respiratory disease, asthma, and allergies. Because children and the elderly are the most vulnerable, they are likely to suffer disproportionately from both warmer temperatures and poorer air quality.

Tropical Diseases Could Migrate to Former Temperate Regions
The prevalence of particular diseases depends largely on local climate. Several serious diseases appear only in warm areas. As the Earth becomes warmer, some of these tropical diseases may be able to spread to parts of the world where they do not currently occur.

Tropical Diseases Could Migrate to Former Temperate Regions
Diseases that are spread by mosquitoes and other insects could become more prevalent. Such “vector-borne” diseases include malaria, dengue fever, yellow fever, and encephalitis. Some scientists believe that algal blooms could occur more frequently as temperatures rise.

Geographic distribution of organisms
Changes to Ecosystems Geographic distribution of organisms Low-lying islands and shorelines Coral reefs

Challenges to Agricultureand the Food Supply
Climate strongly affects crop yields. Yields will fall in regions where drought and heat stress will increase. In regions that will receive increased rainfall and warming temperatures yields should increase. However, episodes of severe weather will cause crop damage that will affect yields. A warmer climate would reduce flexibility in crop distribution and increase irrigation demands. Expansion of the geographic ranges of insect pests could also increase vulnerability and result in greater use of pesticides

17.7 Addressing Climate Change
Improving energy efficiency has the double impact of reducing carbon dioxide release and conserving the shrinking supplies of energy resources. It makes sense to increase energy efficiency even if global warming is not a concern.

Energy Efficiency and Green Energy
One way to stimulate a move toward greater efficiency would be to place a tax on the amount of carbon individuals and corporations release into the atmosphere. This would increase the cost of fuels and stimulate a demand for fuel efficient products because the cost of fuel would rise. It would also stimulate the development of alternative fuels with a lower carbon content and generate funds for research in many aspects of fuel efficiency and alternative fuel technologies.

Increases in energy efficiency and reductions in greenhouse gas emissions are likely to have important related benefits that could offset the costs. Greater energy efficiency would lead to reduced air pollution, which would result in lower health care costs and time lost from work. A study of air pollution in China determined that there were 1.2 million premature deaths in China in 2010.

Green sources of energy such as wind, solar, and hydroelectric, as well as nuclear power do not release carbon dioxide. Switching to green sources of energy is the most effective way to reduce carbon dioxide emissions.

The Role of Biomass Since carbon is an important component of living things, what happens to biomass has a role to play in determining atmospheric carbon dioxide. Forests consist of many long-lived tree species that can tie up carbon for centuries

Forests Store Carbon

The Role of Biomass Preserving forests slows the rate of increase of atmospheric carbon dioxide. This is particularly true for tropical forests since they are the last remaining major unmodified forested areas in the world and they are very efficient at capturing carbon dioxide. The burning of tropical rainforests to provide farm or grazing land Adds carbon dioxide to the atmosphere Reduces the rainforests’ ability to remove carbon dioxide from the atmosphere A commonly cited estimate is that 20 percent of the additional carbon dioxide entering the atmosphere is due to deforestation.

The Role of Biomass Planting trees has also been supported as a way to reduce atmospheric carbon dioxide. Critics argue that this approach will provide only a short-term benefit. Eventually, the trees will mature and die, and their decay will release carbon dioxide into the atmosphere at some later time.

Technological Approaches
The U.S. Department of Energy has concluded that, relying primarily on already proven technology, the United States could reduce its carbon emissions by almost 400 million metric tons. This is enough to stabilize U.S. emissions at 1990 levels.

Many different kinds of technological approaches have been suggested as ways to limit the amount of carbon dioxide added to the atmosphere: Alternative energy sources like wind, solar, hydroelectric, geothermal, and nuclear power do not release carbon dioxide and can replace current fossil-fuel energy sources. However, since fossil fuels currently provide nearly 90 percent of the world’s energy, converting to a greater reliance on nonfossil-fuel energy sources will require a great deal of new construction and technological improvements.

Another approach to the carbon dioxide problem is to prevent it from being released into the atmosphere. Carbon dioxide can be reacted with other compounds to produce solid carbonate minerals (limestone is calcium carbonate) that could be stored in landfills and prevent the release of carbon dioxide gas. It is also possible to capture and store carbon dioxide underground, particularly in saline groundwater deposits and exhausted oil and gas production wells.

However, all of these technological changes come with a cost that will be reflected in the price of energy to the consumer. Thus, as long as fossil-fuel sources of energy are less expensive than non-fossil-fuel alternatives and removing carbon dioxide adds significantly to the cost of energy, there will need to be government policies that stimulate the deployment of these technologies.

International Agreements
The phasing out of CFCs required significant technological changes, but the changes were very rapid once a broad international consensus was reached and a plan established. Recent data show that CFCs in the atmosphere have begun to decline. Although CFCs are a minor player in the climate change scenario, the changes made to protect the ozone layer have had the side benefit of reducing the release of a potent greenhouse gas.

1997 Kyoto Protocol A first step toward a worldwide approach to alleviating the problem. Most countries of the world ratified the treaty. Although the United States did not officially ratify the treaty, it has been an active participant in the series of climate change conferences held in recent years.

Under the Kyoto Protocol only the economically developed countries of the world were required to limit their greenhouse gas emissions to a specific percentage below 1990 levels. They were to meet their targets by 2012. Economically developing countries including nearly all of Latin America, Africa, and Asia did not have binding targets to meet.

In 2006 China became the world’s largest emitter of carbon dioxide and the United States was in second place. The European countries have been most successful in reducing their greenhouse gas emissions. Many of the heavily industrialized countries are actively promoting changes that reduce greenhouse gas emissions.

Other heavily industrialized countries are meeting their goals because of the major economic downturn in many European countries. When the economy is bad, energy use declines and carbon dioxide emissions fall. The Kyoto Protocol expired in 2012 and at a meeting Doha, Qatar in December 2012 an agreement was reached to extend the Protocol through 2020. While Europe in general met its goal for greenhouse gas emissions, most developing countries did not have goals to meet and greenhouse gas emissions have continued to increase.

Summary The concept of climate change is not new.
Geological studies have demonstrated that climates have change greatly over the Earth’s history. Today’s climate change is different in that it is highly likely that it is being caused by human activities. The primary greenhouse gases are carbon dioxide, nitrous oxide, methane, and chlorofluorocarbons. These gases are strongly linked to an increase in the average temperature of the Earth and, consequently, are leading to major changes in the climate.

Summary These include warming of the Earth, particularly near the poles. The warming will result in melting of the permafrost, glaciers, and sea ice; changes in rain and snowfall patterns; shifts in the distribution of plants and animals; more intense heat waves and severe storms; a rise in sea level; and acidification of the oceans. Other likely effects of climate change are health effects in humans, extinction of some plants and animals, flooding of cities, and changes in agricultural productivity.

Summary The primary factor involved in climate change appears to be the carbon dioxide released from the burning of fossil fuels. Since fossil fuel use is closely tied to economic development, many developing countries are unwilling to accept limits to their use of fossil fuels.

ENVIRONMENTAL SCIENCE

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