This website would like to remind you: Your browser (Apple Safari 4) is out of date. Update your browser for more security, comfort and the best experience on this site. Encyclopedic Entry global warming For the complete encyclopedic entry with media resources, visit: http://education.nationalgeographic.com/encyclopedia/global-warming/ Global warming describes the current rise in the average temperature of Earth s air and oceans. Global warming is often described as the most recent example of climate change. Earth s climate has changed many times. Our planet has gone through multiple ice ages, in which ice sheets and glaciers covered large portions of the Earth. It has also gone through warm periods when temperatures were higher than they are today. Past changes in Earth s temperature happened very slowly, over hundreds of thousands of years. However, the recent warming trend is happening much faster than it ever has. Natural cycles of warming and cooling are not enough to explain the amount of warming we have experienced in such a short time only human activities can account for it. Scientists worry that the climate is changing faster than some living things can adapt to it. In 1988, the World Meteorological Organization and the United Nations Environment Programme established a committee of climatologists, meteorologists, geographers, and other scientists from around the world. This Intergovernmental Panel on Climate Change (IPCC) includes thousands of scientists who review the most up-todate research available related to global warming and climate change. The IPCC evaluates the risk of climate change caused by human activities. According to the IPCC s most recent report (in 2007), Earth s average surface temperatures have risen about 0.74 degrees Celsius (1.33 degrees Fahrenheit) during the past 100 years. The increase is greater in northern latitudes. The IPCC also found that land regions are warming faster than oceans. The IPCC states that most of the temperature increase since the mid-20th century is likely due to human activities. The Greenhouse Effect Human activities contribute to global warming by increasing the greenhouse effect. The greenhouse effect happens when certain gases known as greenhouse gases collect in Earth s atmosphere. These gases, which occur naturally in the atmosphere, include carbon dioxide, methane, nitrogen oxide, and fluorinated gases sometimes known as chlorofluorocarbons (CFCs). Greenhouse gases let the sun s light shine onto the Earth s surface, but they trap the heat that reflects back up into the atmosphere. In this way, they act like the insulating glass walls of a greenhouse. The greenhouse effect keeps Earth s climate comfortable. Without it, surface temperatures would be cooler by about 33 degrees Celsius (60 degrees Fahrenheit), and many life forms would freeze. Since the Industrial Revolution in the late 1700s and early 1800s, people have been releasing large quantities of greenhouse gases into the atmosphere. That amount has skyrocketed in the past century. Greenhouse gas 1 of 9
emissions increased 70 percent between 1970 and 2004. Emissions of carbon dioxide, the most important greenhouse gas, rose by about 80 percent during that time. The amount of carbon dioxide in the atmosphere today far exceeds the natural range seen over the last 650,000 years. Most of the carbon dioxide that people put into the atmosphere comes from burning fossil fuels such as oil, coal, and natural gas. Cars, trucks, trains, and planes all burn fossil fuels. Many electric power plants also burn fossil fuels. Another way people release carbon dioxide into the atmosphere is by cutting down forests. This happens for two reasons. Decaying plant material, including trees, releases tons of carbon dioxide into the atmosphere. Living trees absorb carbon dioxide. By diminishing the number of trees to absorb carbon dioxide, the gas remains in the atmosphere. Most methane in the atmosphere comes from livestock farming, landfills, and fossil fuel production such as coal mining and natural gas processing. Nitrous oxide comes from agricultural technology and fossil fuel burning. Fluorinated gases include chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons. These greenhouse gases are used in aerosol cans and refrigeration. All of these human activities add greenhouse gases to the atmosphere, trapping more heat than usual and contributing to global warming. Effects of Global Warming Even slight rises in average global temperatures can have huge effects. Perhaps the biggest, most obvious effect is that glaciers and ice caps melt faster than usual. The meltwater drains into the oceans, causing sea levels to rise and oceans to become less salty. Ice sheets and glaciers advance and retreat naturally. As Earth s temperature has changed, the ice sheets have grown and shrunk, and sea levels have fallen and risen. Ancient corals found on land in Florida, Bermuda, and the Bahamas show that the sea level must have been 5 to 6 meters (16-20 feet) higher 130,000 years ago than it is today. Earth doesn t need to become oven-hot to melt the glaciers. Northern summers were just 3 to 5 degrees Celsius (5-9 degrees Fahrenheit) warmer during the time of those ancient fossils than they are today. However, the speed at which global warming is taking place is unprecedented. The effects are unknown. Glaciers and ice caps cover about 10 percent of the world s landmass today. They hold about 75 percent of the world s fresh water. If all of this ice melted, sea levels would rise by about 70 meters (230 feet). The IPCC reported that the global sea level rose about 1.8 millimeters (0.07 inches) per year from 1961 to 1993, and 3.1 millimeters (0.12 inches) per year since 1993. Rising sea levels could flood coastal communities, displacing millions of people in areas such as Bangladesh, the Netherlands, and the U.S. state of Florida. Forced migration would impact not only those areas, but the regions to which the climate refugees flee. Millions more people in countries like Bolivia, Peru, and India depend on glacial meltwater for drinking, irrigation, and hydroelectric power. Rapid loss of these glaciers would devastate those countries. Glacial melt has already raised the global sea level slightly. However, scientists are discovering ways the sea level could increase even faster. For example, the melting of the Chacaltaya Glacier in Bolivia has exposed dark rocks beneath it. The rocks absorb heat from the sun, speeding up the melting process. 2 of 9
Many scientists use the term climate change instead of global warming. This is because greenhouse gas emissions affect more than just temperature. Another effect involves changes in precipitation like rain and snow. Patterns in precipitation may change or become more extreme. Over the course of the 20th century, precipitation increased in eastern parts of North and South America, northern Europe, and northern and central Asia. However, it has decreased in parts of Africa, the Mediterranean, and parts of southern Asia. Future Changes Nobody can look into a crystal ball and predict the future with certainty. However, scientists can make estimates about future population growth, greenhouse gas emissions, and other factors that affect climate. They can enter those estimates into computer models to find out the most likely effects of global warming. The IPCC predicts that greenhouse gas emissions will continue to increase over the next few decades. As a result, they predict the average global temperature will increase by about 0.2 degrees Celsius (0.36 degrees Fahrenheit) per decade. Even if we reduce greenhouse gas and aerosol emissions to their 2000 levels, we can still expect a warming of about 0.1 degree Celsius (0.18 degrees Fahrenheit) per decade. The panel also predicts global warming will contribute to some serious changes in water supplies around the world. By the middle of the 21st century, the IPCC predicts, river runoff and water availability will most likely increase at high latitudes and in some tropical areas. However, many dry regions in the mid-latitudes and tropics will experience a decrease in water resources. As a result, millions of people may be exposed to water shortages. Water shortages decrease the amount of water available for drinking, electricity, and hygiene. Shortages also reduce water used for irrigation. Agricultural output would slow and food prices would climb. Consistent years of drought in the Great Plains of the United States and Canada would have this effect. IPCC data also suggest that the frequency of heat waves and extreme precipitation will increase. Weather patterns such as storms and tropical cyclones will become more intense. Storms themselves may be stronger, more frequent, and longer-lasting. They would be followed by stronger storm surges, the immediate rise in sea level following storms. Storm surges are particularly damaging to coastal areas because their effects (flooding, erosion, damage to buildings and crops) are lasting. What We Can Do Reducing our greenhouse gas emissions is a critical step in slowing the global warming trend. Many governments around the world are working toward this goal. The biggest effort so far has been the Kyoto Protocol, which was adopted in 1997 and went into effect in 2005. By the end of 2009, 187 countries had signed and ratified the agreement. Under the protocol, 37 industrialized countries and the European Union have committed to reducing their greenhouse gas emissions. There are several ways that governments, industries, and individuals can reduce greenhouse gases. We can improve energy efficiency in homes and businesses. We can improve the fuel efficiency of cars and other vehicles. We can also support development of alternative energy sources, such as solar power and biofuels, that don t involve burning fossil fuels. Some scientists are working to capture carbon dioxide and store it underground, rather than let it go into the atmosphere. This process is called carbon sequestration. 3 of 9
Trees and other plants absorb carbon dioxide as they grow. Protecting existing forests and planting new ones can help balance greenhouse gases in the atmosphere. Changes in farming practices could also reduce greenhouse gas emissions. For example, farms use large amounts of nitrogen-based fertilizers, which increase nitrogen oxide emissions from the soil. Reducing the use of these fertilizers would reduce the amount of this greenhouse gas in the atmosphere. The way farmers handle animal manure can also have an effect on global warming. When manure is stored as liquid or slurry in ponds or tanks, it releases methane. When it dries as a solid, however, it does not. Reducing greenhouse gas emissions is vitally important. However, the global temperature has already changed and will most likely continue to change for years to come. The IPCC suggests that people explore ways to adapt to global warming as well as try to slow or stop it. Some of the suggestions for adapting include: Expanding water supplies through rain catchment, conservation, reuse, and desalination. Adjusting crop locations, variety, and planting dates. Building seawalls and storm surge barriers and creating marshes and wetlands as buffers against rising sea levels. Creating heat-health action plans, boosting emergency medical services, and improving disease surveillance and control. Diversifying tourism attractions, because existing attractions like ski resorts and coral reefs may disappear. Planning for roads and rail lines to cope with warming and/or flooding. Strengthening energy infrastructure, improving energy efficiency, and reducing dependence on single sources of energy. VOCABULARY Term Part of Speech Definition abnormal adjective unusual. adapt verb to adjust to new surroundings or a new situation. aerosol can container of liquid material under high pressure. When released through a small opening, the liquid becomes a spray or foam. agricultural technology the art and science of complex machines used to perform tasks associated with farming and ranching. ancient adjective very old. atmosphere layers of gases surrounding a planet or other celestial body. biofuel energy source derived directly from organic matter, such as plants. buffer a cushion or shield. carbon dioxide greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels. carbonic acid chemical produced as carbon dioxide dissolves in water. carbon sequestration process of capturing carbon emissions and storing them underground. century 100 years. chlorofluorocarbon (CFC) chemical compound mostly used in refrigerants and flame-retardants. Some CFCs have destructive effects on the ozone layer. climate all weather conditions for a given location over a period of time. 4 of 9
climate change gradual changes in all the interconnected weather elements on our planet. climate refugee person forced to leave his or her home and community because of climate change. climatologist person who studies long-term patterns in weather. coal dark, solid fossil fuel mined from the earth. coast edge of land along the sea or other large body of water. committee group of people elected or appointed to perform a task. conservation management of a natural resource to prevent exploitation, destruction, or neglect. consistent adjective maintaining a steady, reliable quality. cope verb to handle or deal with problems. coral tiny ocean animal, some of which secrete calcium carbonate to form reefs. coral reef rocky ocean features made up of millions of coral skeletons. critical adjective very important. cyclone weather system that rotates around a center of low pressure and includes thunderstorms and rain. Usually, hurricanes refer to cyclones that form over the Atlantic Ocean. data plural (singular: datum) information collected during a scientific study. decade 10 years. decay verb to rot or decompose. desalination process of converting seawater to fresh water by removing salt and minerals. devastate verb to destroy. diminish verb to become smaller or less important. dissolve verb to break up or disintegrate. diverse adjective varied or having many different types. drought period of greatly reduced precipitation. electricity set of physical phenomena associated with the presence and flow of electric charge. emission discharge or release. encore reappearance by a performer after the end of the performance. energy efficiency use of a relatively small amount of energy for a given task, purpose, or service; achieving a specific output with less energy input. erosion act in which earth is worn away, often by water, wind, or ice. establish verb to form or officially organize. 5 of 9
European Union association of European nations promoting free trade, ease of transportation, and cultural and political links. evaluate verb to decide something's worth. farming the art, science, and business of cultivating the land for growing crops. fertilizer nutrient-rich chemical substance (natural or manmade) applied to soil to encourage plant growth. flee verb to run away. fluorinate verb to add or combine with the element fluorine (F). forest ecosystem filled with trees and underbrush. fossil remnant, impression, or trace of an ancient organism. fossil fuel coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals. freeze weather pattern of temperatures below 0 degrees Celsius (32 degrees Fahrenheit). fuel efficiency ability to produce as much power with as little fuel consumed as possible. geographer person who studies places and the relationships between people and their environments. glacier mass of ice that moves slowly over land. global warming increase in the average temperature of the Earth's air and oceans. Great Plains grassland region of North America, between the Rocky Mountains and the Mississippi River. greenhouse building, often made of glass or other clear material, used to help plants grow. greenhouse effect phenomenon where gases allow sunlight to enter Earth's atmosphere but make it difficult for heat to escape. greenhouse gas gas in the atmosphere, such as carbon dioxide, methane, water vapor, and ozone, that absorbs solar heat reflected by the surface of the Earth, warming the atmosphere. heat-health action plan public system for preventing or reducing death and disease due to extreme heat waves. heat wave period of unusually hot weather. hydrochlorofluorocarbon greenhouse gas often used as an industrial cooling material. hydroelectric power usable energy generated by moving water converted to electricity. hygiene science and methods of keeping clean and healthy. ice age long period of cold climate where glaciers cover large parts of the Earth. The last ice age peaked about 20,000 years ago. Also called glacial age. ice cap area of fewer than 50,000 square kilometers (19,000 square miles) covered by ice. ice sheet thick layer of glacial ice that covers a large area of land. 6 of 9
industrialization growth of machine production and factories. Industrial Revolution change in economic and social activities, beginning in the 18th century, brought by the replacement of hand tools with machinery and mass production. infrastructure structures and facilities necessary for the functioning of a society, such as roads. insect type of animal that breathes air and has a body divided into three segments, with six legs and usually wings. Intergovernmental Panel on Climate Change (IPCC) group of scientists who review the most up-to-date research available related to global warming and climate change. irrigation watering land, usually for agriculture, by artificial means. Kyoto Protocol (1997) international agreement to reduce greenhouse gas emissions. landfill site where garbage is layered with dirt and other absorbing material to prevent contamination of the surrounding land or water. landmass large area of land. latitude distance north or south of the Equator, measured in degrees. livestock, plural animals raised for sale and profit. manure animal excrement or waste used to fertilize soil. marsh wetland area usually covered by a shallow layer of seawater or freshwater. meltwater freshwater that comes from melting snow or ice. meteorologist person who studies patterns and changes in Earth's atmosphere. methane chemical compound that is the basic ingredient of natural gas. migration movement of a group of people or animals from one place to another. model image or impression of an object used to represent the object or system. multiple adjective many. natural gas type of fossil fuel made up mostly of the gas methane. nitrogen chemical element with the symbol N, whose gas form is 78% of the Earth's atmosphere. nitrous oxide greenhouse gas used in medicine and the manufacture of rockets. Also known as laughing gas or happy gas. oil fossil fuel formed from the remains of marine plants and animals. Also known as petroleum or crude oil. penguin bird native to the Antarctic. power plant industrial facility for the generation of electric energy. precipitation all forms in which water falls to Earth from the atmosphere. protocol series of rules. 7 of 9
rain catchment system to collect and store rainwater. ratify verb to formally approve or confirm. refrigerant substance used to keep materials cool. research scientific observations and investigation into a subject, usually following the scientific method: observation, hypothesis, prediction, experimentation, analysis, and conclusion. runoff overflow of fluid from a farm or industrial factory. sea level base level for measuring elevations. Sea level is determined by measurements taken over a 19-year cycle. seawall barrier built to protect a beach or shoreline from erosion. Also called a bulkhead. ski resort facility where people can ski for recreation or sport. skyrocket verb to increase rapidly. slurry liquid waste, such as that from the coal mining and cleaning process, also called sludge. snow precipitation made of ice crystals. solar power rate of producing, transferring, or using solar energy. spruce coniferous, or cone-bearing, tree. storm severe weather indicating a disturbed state of the atmosphere resulting from uplifted air. storm surge abnormal rise in sea level accompanying a hurricane or other intense storm. Also called a storm tide. storm surge barrier walls or obstacles built to prevent ocean or river water from flowing into an area after a storm. Also called levee or floodgate. surveillance observation of a person, community, or situation. temperature degree of hotness or coldness measured by a thermometer with a numerical scale. tourism the industry (including food, hotels, and entertainment) of traveling for pleasure. tropical adjective existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south. United Nations Environment Programme organization whose mission is to provide international leadership and encourage partnerships in caring for the environment. unprecedented adjective never before known or experienced. vital adjective necessary or very important. water shortage reduction in the amount of fresh water available for drinking, hygiene, and industrial and agricultural use. 8 of 9
water supply amount of available fresh water for drinking, hygiene, and industrial and agricultural use. weather pattern repeating or predictable changes in the Earth's atmosphere, such as winds, precipitation, and temperatures. wetland area of land covered by shallow water or saturated by water. World Meteorological Organization United Nations agency that studies the Earth's atmosphere, its interaction with the oceans, the climate, and the distribution of water resources. For Further Exploration Audio & Video National Geographic Video: Global Warming 101 Images Food and Agriculture Organization: FactFile Global Warming Worksheets & Handouts United Nations Environment Programme: Climate Change Toolkit Websites National Geographic Environment: Global Warming 1996 2015 National Geographic Society. All rights reserved. 9 of 9