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Climate Change, Greenhouse Effect and Global Warming Earth’s Climate: A Dynamic System The Earth is a unique planet where our atmosphere, the oceans and soils combine to support a web of life of diversity and continual change. The daily needs of more than six billion people now stress the limits of this naturally regulated system. Is Our Climate Changing? Weather changes both rapidly and slowly. The passage of a thunderstorm can change a bright sunny day into a dark, windy, rainy one in less than an hour. Farmers know that in one year the amount and timing of rainfall can be nearly ideal for growing crops, while the next year might bring drought or floods. In some years no hurricanes reach the Atlantic Coast, while in other years coastal states are battered by one storm after another. All of these things are dictated by the Earth’s climate. Is the Earth’s climate changing? One extreme summer in the United States can’t answer that question. Our picture of the climate develops slowly as we watch many seasons pass. Only by comparing measurements taken over many years and decades can we sense the shifting patterns of climate. The hottest ten years in recent history have taken place since 1987. Climate is a complex system that ties together the atmosphere, oceans, land surface and the living kingdoms of plants and animals. Climate describes the weather over a long period of time. The Earth has experienced major climate changes long before humans inhabited the planet. The dinosaurs roamed a world much warmer than today. The Earth has also gone through an ice age that sent massive glaciers spreading over North America and Europe. Animals and plants have been forced to either go extinct or to adapt to new conditions. Such natural shifts in climate have distinguished the different eras in Earth’s history. Climate change is a natural phenomenon due to solar variability, volcanic activity, biological evolution and El Nino. These changes can influence global warming and global cooling. We now face the prospect of a different kind of climate change. Many scientists believe this change is being brought on primarily by human actions. Our industry, agriculture and daily living cause important gases such as carbon dioxide (CO2) and methane (CH4) to accumulate in the atmosphere. Scientists predict severe consequences may await us in the not too distant future if we do not change our behaviors. The Light from Above If we were to look at our Earth from space, we would see a multi-colored sphere. Clouds and snowcoated lands create patches of cottony white that interweave with the royal blue background of the oceans. Breaks in the cloud cover would reveal the continents as brown hues while lighter splotches of color indicate desert regions. The white areas make Earth a bright planet. About 30% of the sun’s radiation gets reflected immediately back into space by the Earth’s atmosphere and snow. This is called the Albiedo Effect. Solar energy that doesn’t reflect off clouds and snow is absorbed by the atmosphere and surface of 1 the Earth. As the surface warms, it sends infrared radiation, or heat, back toward space. This type of radiation resembles the warmth we feel when sitting at a distance from a hot stove or campfire. Aside from gases in the atmosphere, clouds also play a major climatic role. By reflecting solar radiation away from Earth, some clouds cool the planet. Satellite measurements have recently proved that clouds exert a powerful cooling effect on the Earth. In some areas, such as the tropics, heavy clouds may markedly warm the regional climate by reflecting the infrared heat back towards the Earth. This trapping of heat near the surface contributes to the Earth’s natural greenhouse effect. Clouds and greenhouse gases fit into something called the global radiation budget. Just like a well-constructed economic budget, the radiation budget must balance itself. Solar energy reaching Earth must equal the energy leaving the planet otherwise the oceans would eventually boil away or freeze solid. Scientists warn that we are currently upsetting the Earth’s radiation balance through activities such as burning fossil fuels and cutting forests. These actions cause carbon dioxide and other gases to accumulate in the air and therefore strengthen Earth’s greenhouse effect. We expect the planet’s surface will warm up until a new radiation balance emerges. The Greenhouse Effect Looking at other planets, we can see both stronger and weaker greenhouse effects than that of Earth. Our nearest neighbor, Venus, has a thick cloak of carbon dioxide that heats the planet’s surface to an average of 4200 C. Mars, with a mean surface temperature hovering around –500C, has a very thin atmosphere that provides little greenhouse warming. Earth’s atmosphere lets in rays of sunshine and they warm the surface. The planet keeps cool by emitting heat back into space in the form of infrared radiation. But while the atmosphere is 2 How do scientists study past climates? If scientists had to rely on written weather records for historical climate information, they would be in trouble. Such records only exist for the last 150 years or so. However, clues in the environment can provide information from thousands of years ago. Ice cores -- Ice in polar-regions contains air bubbles trapped thousands of years in the past. Scientists can check the gases in the bubbles and provide a good estimate of the temperature at that time. Also, the thickness of the ice layers gives information about past climates. Tree rings -- Trees can live for centuries, and for each year of their lives they add a ring of growth to their diameter. The width of these rings can give scientists information about climate during that year of growth. Fossils -- The bones of long-dead animals indicate which species lived in certain areas and when they were there. Since each species has a set of food and temperature requirements, scientists can deduce the climate of their time and area. Sediment cores -- Columns of sediment from lake bottoms contain pollen grains in each layer. The farther down the layer, the older the sediment. After determining the age of the layers, scientists can study what plants were growing when the sediment was deposited. Archaeological records -- Humans have left their traces throughout the world for ages. How they lived and what they needed to survive provide important clues about the climates they experienced. fairly transparent to sunshine, it is almost opaque to infrared radiation. It traps the heat inside much like a garden greenhouse. About 70% of the solar energy that reaches Earth passes through the atmosphere and is absorbed at the surface. About 90% of the infrared radiation emitted by the surface is re-absorbed by the atmosphere before it can slowly escape to space. The layer of air surrounding the Earth contains important gases such as water vapor and carbon dioxide. These gases absorb the heat radiated by the Earth’s surface and reemit their own heat at much lower temperatures. The atmosphere “traps” the Earth’s radiation. This planetary warming mechanism is called the “greenhouse effect.” The greenhouse effect is good, without it we would not be able to live here. The atmosphere saves us from a frigid fate. If all greenhouse gases were removed from the atmosphere, the average surface temperature of Earth would drop from its current value of 60°F (15°C) to about 0°F (-18°C). Earth would be a frozen and nearly lifeless planet without the greenhouse effect. It is the distinctive molecular structures of the greenhouse gases that make them strong absorbers and emitters of infrared radiation. About 99% of air molecules are nitrogen (N2) and oxygen (O2). They have simple structures consisting of two identical atoms. They have a relatively minor effect on the transmission of solar and infrared radiation through the atmosphere because of this simple structure. Molecules with three or more atoms like water vapor (H2O), carbon dioxide (CO2), ozone (O3) and a host of other trace gases can efficiently absorb and emit (give off) infrared energy. Though some of these gases make-up only a tiny fraction of the atmosphere they can make significant contributions to the greenhouse effect. The molecule that makes the largest contribution is water vapor. Water vapor is the most important greenhouse gas. Because we have no direct control over it we focus on the other greenhouse gases that we have more control over. An average water molecule stays in the atmosphere only a few days from the time it evaporates from the surface to the time it falls out of the atmosphere as precipitation. Because of this the water vapor content of the atmosphere adjusts quickly to changes in surface temperature. Why Are Greenhouse Gas Amounts Increasing? Carbon dioxide gas makes-up a tiny fraction of the atmosphere. Only about one air molecule in three thousand is CO2. Yet, despite their small numbers, CO2 molecules can have a big affect on the climate. Carbon dioxide (CO2) has a much longer lifetime in the atmosphere than water vapor. It can take 100 to 200 years to establish a new atmospheric balance if CO2 is suddenly added to the atmosphere. That’s because the carbon in CO2 is cycled between the atmosphere and the ocean or land surface by slow chemical and biological processes. Plants, for example, use CO2 to produce energy in a process known as photosynthesis. Through millions of years of Earth’s history, trillions 3 of tons of carbon were taken out of the atmosphere by plants and buried in sediments that eventually became coal, oil or natural gas deposits. In the last two centuries humans have used these deposits at an increasing rate as an economical energy source. In a similar way, cement manufacture releases carbon atoms buried in carbonate rocks. Today human activities release about 5.5 billion tons of carbon to the atmosphere every year through burning fossil fuels and cement manufacturing. Approximately another 1.5 billion tons per year are released through land use changes such as deforestation. These releases result in an increase of atmospheric CO2 of about one-half percent per year. The burning of coal, oil and natural gas and the destruction of forests has raised the total amount of atmospheric carbon dioxide by nearly 30% since the beginning of the industrial revolution in the early 1800’s. Other naturally occurring greenhouse gases such as methane and nitrous oxide have been increasing. Entirely man-made greenhouse gases such as CFC’s have also been introduced into the atmosphere. Many of these gases are increasing more rapidly than carbon dioxide. The amount of methane, or natural gas, in the atmosphere has doubled since the Industrial Revolution. Greenhouse Gases and Global Warming Since the Industrial Revolution, however, atmospheric concentrations of the most important human-influenced greenhouse gases – CO2, methane and nitrous oxide – have increased at an unnatural rate. In the last 200 years, CO2 levels have risen almost 30%, methane levels have gone up 145%, and nitrous oxide levels have increased by 15%. Each greenhouse gas differs in its ability to absorb heat in the atmosphere. Where are all these "extra" greenhouse gases coming from? They are coming from our daily activities. Large-scale burning of fossil fuels for industry and motor vehicles, intense agricultural activity, population growth, land practices, mining and other human activities pump more and more greenhouse gases into the atmosphere, creating a heightened greenhouse effect that leads to a higher average global temperature. This is called global warming. While water vapor is the most important Greenhouse Gas, humans have very little control over it. Carbon dioxide (CO2) is the greenhouse gas that humans are contributing to most directly. Carbon dioxide is a colorless, odorless gas which was naturally in the air before humans were around. Now we continue to emit the gas into the air with our cars, our manufacturing, burning of rain forests and our cutting down of trees. The destruction of trees creates a shortage of plants to remove CO2 from the air. We also release CO2 into the atmosphere when we burn fossil fuels for the generation of electricity. Methane (CH4), also called marsh gas, is another greenhouse gas that was in the air, naturally, before humans. It is used in industries as starting material for many other chemicals. This gas is 4 lighter than air, colorless, odorless, nontoxic, and highly flammable. It is created naturally from decomposing matter in swamps. Methane comes from cow burps, coal mining, natural gas fumes, landfills and wood burning. Methane is also the gas your stomach may release after a hearty meal. In other words, when animals burp, they release methane and add to global warming. Methane traps over 21 times more heat per molecule than carbon dioxide. CFCs or chlorofluorocarbons (also called Halocarbons) were never naturally in the air. They were first manufactured in the 1940s. Because they do not readily react with other chemicals they can have a lifetime in the atmosphere of more than 100 years. This gas was used mostly in aerosol sprays cans such as spray paint and hair spray, refrigeration units, air conditioning, cleaning solvents and packing materials. Using CFCs in aerosol sprays has now been banned in the United States and most other parts of the world. Not only is it a greenhouse gas and keeps infrared light from leaving, but it also damages the ozone layer. The ozone layer is a layer in the upper atmosphere that keeps the sun's harmful ultraviolet rays from reaching us. Global warming and ozone destruction have little to do with each other. CFCs trap more heat than any of the other greenhouse gases. Nitrous oxide (N2O) is given-off during agricultural and industrial activities and during combustion of solid waste and fossil fuels. Nitrous oxide (N20) is more known under the nickname laughing gas. Nitrous oxide, also called nitrogen monoxide, is a colorless, odorless, nonflammable gas which may also attack the ozone layer. It is used in industry as an aerosol propellant. Nitrous oxide absorbs 310 times more heat per molecule than carbon dioxide. Sources and Sinks 5 The elements that compose greenhouse gases, (carbon, oxygen, nitrogen, etc.), normally cycle through the environment between sources and sinks freely. Sources release elements to the atmosphere. Sinks store the elements. Soil, oceans and trees tend to act as natural sinks for carbon. Each year hundreds of billions of tons of carbon, in the form of CO2, are absorbed by soils, oceans and trees. When trees are cut down and burned, the stored carbon is released into the atmosphere as carbon dioxide. The burning of trees is a carbon source. For two centuries, we've been releasing greenhouse gases into the atmosphere at unprecedented rates while destroying forests and other natural sinks that could absorb those gases. We've created a greenhouse that’s a little too effective while trying to improve the quality of life. The Consequences of Too Many Greenhouse Gases If the climate cycle were to follow its natural course, in a few thousand years the Earth would start sliding into another ice age. But our activities threaten to send the climate speeding in another direction toward global warming. The build-up of greenhouse gases and other gases have already enhanced the Earth’s greenhouse effect. It may take several decades to feel the warming because atmospheric temperatures will rise significantly only after the oceans of the world have slowly warmed. The increase in temperature postponement may seem like an advantage. It gives us more time to prepare. However, the time lag could lead us to underemphasize the importance of the problem while we still have a chance to prevent drastic climate change. We have already committed ourselves to some degree of warming even if we could instantly halt the buildup of greenhouse gases in the atmosphere. As human population and economic activities continue to grow, carbon dioxide emissions could double again in the next three decades unless the nations of the world limit their consumption of fossil fuels. Such action would benefit society in many ways. Through energy conservation we can save substantial amounts of money and help reduce our nation’s dependence on foreign fuels. Despite our uncertainty about future climate change we are already beginning to take certain steps that will slow the buildup of greenhouse gases. 6 Global Warming and Wisconsin Global warming: It’s a phrase that has been heard on weather broadcasts and news reports, in science classrooms and around supper tables since the early 1990s. It is a concept that seems far removed from our everyday lives, something that concerns scientists digging into polar ice caps thousands of miles away – not us in Wisconsin. But global warming and the changes it could cause in world climate should concern us. Historical records indicate the average global temperature increased in Wisconsin by 0.50 to 10 F between 1890 and 1990. Thus, the Earth has warmed. This is where the term global warming comes from. In the next 100 years, scientists predict the temperature may rise another 20 to 60 F. Such increases have occurred previously in Earth’s history, but never over such a short time span. In fact, the average global temperature has risen more in the last century than at any time in the past 10,000 years. The great majority of scientific research agrees that between now and the end of this century the globe will continue to warm up. It is difficult to predict what an increase in global temperature will bring because of the various climatic factors. However, the results could significantly alter life in Wisconsin. All of the items listed below are potential changes Wisconsin could face: wetter winters and drier summers with longer, hotter and more frequent heat waves weather and climate changes that could require farmers to raise different crops dairy cattle and other livestock stressed by heat exhaustion and growing pest populations poor air quality and higher concentrations of ground-level ozone could causes health problems warmer and more shallow river waters could hurt populations of cold-water fish like trout denser algae blooms and lower oxygen levels in ponds and lakes more frequent floods, droughts, forest fires and damaging storms changes in tree species that could affect the forestry industry and wildlife populations increases in disease-carrying insect populations The Effects of Global Warming on Wisconsin Because the models scientists use to study climate change are not precise enough to offer specific predictions for an area as small as the state of Wisconsin, the following discussion is taken from predictions for the upper Midwest region. While it’s fairly safe to say that global climate change won’t turn our state into a tropical paradise, scientists agree that it could significantly alter the way we live. Weather and Climate The upper Midwest may become warmer and wetter, with the 7 average temperature increasing by about 40 F. The increase doesn’t mean we’d simply up the daily temperature by 4 degrees. A more likely scenario is that summer heat waves would be longer and hotter and nighttime winter temperatures would not sink so low. Precipitation could increase by as much as 10% on average, but much of the increased precipitation would come in the form of intense storms, leading to flooding and more runoff. Precipitation patterns could also change, with more rain coming in the winter and less in the summer. Less rain in the summer, paired with increased evaporation caused by warmer temperatures, could trigger severe summer droughts. Water Resources Lake Superior water levels could drop over time by 1 to 1.5 feet, while Lake Michigan levels could fall 3 to 8 feet. Such drops could result from longer and drier summers during which more of the lakes’ waters would be claimed by evaporation. Winters might have less snow and shorter periods of snow cover. Lowered Great Lakes levels could strike a heavy blow to industries like shipping and hydropower generation. Smaller inland lakes could also get shallower. Some ponds and wetlands might disappear, jeopardizing wildlife habitat, tourism and recreation industries. Groundwater levels could drop significantly threatening drinking water quality and quantity due to increased concentrations of pollutants. Warmer water would encourage algae blooms and other aquatic plant overgrowth in the summer. This would transform clear blue waters into a thick, smelly pea soup that turns off boaters, anglers and swimmers. Algae blooms also make survival difficult for fish and other aquatic species. Coldwater species like trout could decline in number or disappear from their traditional areas altogether. Decreased winter ice cover could disturb both lake ecology and the ice fishing season. Agriculture Anything that affects farming affects the state’s economy. Southern Wisconsin farms may begin to resemble those in present-day Kansas. Wheat would do well, but the ideal range for corn and soybeans would shift northward, and these crops might not grow as well in the soils of northern Wisconsin. High levels of carbon dioxide in the atmosphere may actually increase crop production, because certain plants can become larger and more productive in a CO2–rich environment. However, gains in crop productivity might be counter-balanced by more frequent and severe droughts, and by more weed, pest and disease problems. Dairy and other livestock farmers might see productivity decline as their herds suffer from heat stress, the feed supply is disrupted (from changing crop yields), and the water supply reduced. Warmer, longer summers might encourage the growth of pest populations that could further stress livestock and spread disease. Forests and Wildlife As temperature and precipitation patterns change, habitat ranges for plants and animals are expected to shift northward. Some species might be able to migrate with their ideal habitat, but others, especially those already endangered, could face extinction. Researchers predict that mixed northern hardwood and oak forests would be transformed to oak savannas and grasslands within 30 to 60 years. Typical northern forests could completely disappear from Wisconsin along with the eastern hemlock and the sugar maple. 8 Human Health More frequent and severe heat waves would threaten the elderly, especially those living alone, and people suffering from cardiovascular and respiratory diseases. The U.S. Environmental Protection Agency (EPA) projects that a 30 F warming could almost double heat-related deaths in Milwaukee during a typical summer, from 30 to about 55. A longer, hotter summer, along with increased emissions from power plants trying to keep up with greater air conditioning demands, would likely intensify air pollution problems. This could result in more and more serious cases of asthma, emphysema and lung disease for Wisconsin residents. Wisconsin’s allergy season could lengthen because some plants would flourish in the extended summer. Warmer weather might also be beneficial to disease-carrying insects like mosquitoes and ticks, leading to more cases of Lyme disease, tick-borne encephalitis and possibly even malaria. Finally, more frequent severe weather events like forest fires, floods and dangerous storms could cause injuries and take lives and damage properties. All of these would increase insurance rates. Responding to a Global Threat The Wisconsin Department of Natural Resources (DNR) has completed several studies showing that the use of energy-efficient technologies could reduce the state’s emissions of greenhouse gases with little or no net cost. One study showed that if Wisconsin adopted improved energy efficiency measures, we could realize a 12.5 million ton decrease in the growth of greenhouse gas emissions by 2010 (compared to projected levels) and save $490 million in energy expenditures at the same time. Another study predicted that investing in energy efficiency measures could create a $490 million increase in disposable income, a $41 million increase in gross state product and 8,500 new jobs in 2010. In 1992, 154 nations and the European Union adopted the United Nations Framework Convention on Climate Change. It was a voluntary agreement to stabilize greenhouse gas emissions at 1990 levels. In December 1997 at a United Nations meeting in Kyoto, Japan, some industrialized countries went a step further and agreed to the Kyoto Protocol, which required developed nations to reduce their greenhouse gas emissions to an average of 5% below 1990 levels by 2008-2012. Specific reduction commitments varied among nations. If the protocol had gone into effect for the U.S., it would have required the U.S. to reduce greenhouse gas emissions to 7 percent below 1990 levels. The U.S. refused to sign the Kyoto Protocol. At current rates of activity, our nation stands to increase its emissions to 30% above 1990 levels by 2010. Our country is already the world’s largest emitter of greenhouse gases, contributing approximately 23% of global emissions despite having only 5% of the world’s population. How Can We Help? Many of the things we can do to reduce greenhouse gas emissions offer personal benefits as well. The biggest contribution individuals can make is to use less energy. By tuning cars, insulating homes and using energy-efficient appliances, we can decrease our use of fossil fuels and save money. We can car pool, use public transportation, walk or bike to our destinations. These activities cut fuel consumption, decrease traffic congestion, decrease emissions of other air pollutants and may even help us become healthier. Finally, we can purchase items with reusable, recyclable, or 9 reduced packaging. All of these options help decrease the amount of energy and resources being used to make new packaging. Those willing to invest even more in guarding against climate change have further options. Alternative energy sources like solar power, wind power and geothermal heat pumps can supply home energy needs. Vehicles using propane, natural gas or ethanol, fuels that burn cleaner than gasoline, are already on the roads. Hybrid cars, which use electricity from batteries along with gasoline for power, are another viable alternative for transportation. Solar-powered cars and fuelcell cars, powered by hydrogen, may be available within the next 10 years. Global Warming and Sea Level Rise One of the most significant potential impacts of climate change is sea level rise that may cause flooding of coastal areas and islands, shoreline erosion, and destruction of important ecosystems such as wetlands. River water salinity may also be an issue. As global temperatures increase, sea level rise already underway is expected to accelerate due to a thermal expansion of upper layers of the ocean and melting of glaciers. Over the last 100 years, the global sea level has risen by about 10 to 25 cm. On this time scale, the warming and the consequent thermal expansion of the oceans may account for about 2-7 cm of the observed sea level rise, while the observed retreat of glaciers and ice caps may account for another 2-5 cm. Other factors are more difficult to measure. The rate of observed sea level rise suggests that there has been a net positive contribution from the huge ice sheets of Greenland and Antarctica, but observations of the ice sheets do not yet allow meaningful measurement estimates of their contributions. The ice sheets remain a major source of uncertainty in accounting for past changes in sea level because of insufficient data about these ice sheets over the last 100 years. Warmer temperatures also increase precipitation. Snowfall over Greenland and Antarctica is expected to increase by about 5 percent for every 1°F warming in temperatures. Increased snowfall tends to cause sea level to drop if the snow does not melt during the following summer, because the only other place for the water to be is the ocean. (The amount of water in the atmosphere is less than 10 Dairy and other livestock farmers may see productivity decline as a result of __43__ in their animals. If the U.S. had adopted the Kyoto Protocol, we would have been required to reduce greenhouse gas emissions to __44__% below 1990 levels by 2008-2012. However, at the current rates our nation stands to increase its emissions to 30 percent above 1990 levels by 2010. The U.S. is the world’s largest emitter of greenhouse gases, contributing approximately __45__% of global emissions despite having only __46__% of the world’s population. The biggest contribution individuals can make is to __47__. Considering all of these factors, the Intergovernmental Panel on Climate Change (IPCC) estimates that sea level will rise __48__ cm by the year 2100. List the nine potential changes Wisconsin could face if global warming continues: (write out) 49. 50. 51. 52. 53. 54. 55. 56. 57. List five of the clues scientists use to study past climates: 58. 59. 60. 61. 62. Short Answer Questions: Write the answers to these questions in your notebook. 63. What is the difference between climate and weather? 64. What is the greenhouse effect and why is it important to life on Earth? 65. What is the difference between global warming and climate change? 66. How does nature contribute to climate changes? 67. How have humans contributed to the global warming? 15