The Greenhouse Effect. Sunlight heats the Earth. Some heat radiated by earth absorbed by gases in the troposphere, warms the air. process of heat absorption called the greenhouse effect G reenhouse gas: can absorb and radiate infrared radiation from the sun
The Greenhouse Effect • Sunlight heats the Earth. • Some heat radiated by earth absorbed by gases in the troposphere, warms the air. • process of heat absorption called the greenhouse effect • Greenhouse gas:can absorb and radiate infrared radiation from the sun • mainly water vapor, carbon dioxide, aslo CFCs, methane, and nitrous oxide.
Measuring Carbon Dioxide in the Atmosphere • Started in 1958, an instrument at the top of a tall tower on the volcano Mauna Loa in Hawaii, far away from forests and cities. • After a few, obvious that the levels were undergoing changes other than seasonal fluctuations. • High carbon dioxide levels of winter were higher, and each year, the summer levels did not fall as low.
Greenhouse Gases and the Earth’s Temperature • Greenhouse gases trap heat near the Earth’s surface, result is an increase in global temperature • Releasing more carbon dioxide than any other greenhouse gas into the atmosphere • power plants, cars, trees burned in tropical rainforest to clear land • carbon dioxide levels, average global temperatures for the past 400,00 years support view
How Certain is Global Warming? • Global warming: gradual increase in the average global temperature due to a higher concentration of gases (such as CO2) in the atmosphere. • Average global temperature increased during the 20th century, predict ion warming trend will continue • Some scientists believe that the warming is part of natural climatic variability
Modeling Global Warming • Predictions based on computer models that predict how temperature, rainfall patterns, and sea level will be affected • Models are becoming more reliable as more data are available, additional factors are considered, and faster computers are built.
The Consequences of a Warmer Earth • A global rise in sea level • Coastal wetlands, and other low-lying areas could be flooded • Salinity of bays and estuaries, freshwater aquifers might increase
A change in global weather patterns • a warmer earth makes hurricanes and typhoons more common • may cause a change in ocean current patterns, shutting off the Gulf Stream • flooding could occur in some regions, droughts other regions
Human health problems • Increase in heat related deaths • Increase ground level ozone causing respiratory illnesses, especially in urban areas • Warmer temperatures enable mosquitoes (carry malaria, encephalitis, other diseases) to increase in number
Agriculture • severely if extreme weather such as drought, became more frequent. • higher temperatures could result in decreased crop yields. • demand for irrigation could increase, further deplete aquifers that have already been overused.
Effects on Plants • alter the range of plant species, change the composition of plant communities. • forests could shrink in areas in the southern part of their range and lose diversity
Effects on Animals • a shift in the geographical range of some animals. • Northern birds may not migrate as far south during the winter. • warming of ocean surface waters might reduce zooplankton that many marine animals depend on for food • warming tropical waters may kill algae that nourish corals, thus destroying coral reefs
Recent Findings • The International Panel on Climate Change (IPCC) • average global surface temperature increased by 0.6ºC during the 20th century • snow and ice cover has dropped • global sea level has risen • atmospheric gases have continued to increase as a result of human activities
Reducing the Risk • Kyoto Protocol: International treaty. Developed countries agree to reduce their emissions of carbon dioxide and other gases that may contribute to global warming by the year 2012. • Not ratified by United States • Some nations and organizations have engaged in reforestation projects to reduce carbon dioxide.
Problems • Economic, political, and social factors faced by different countries cause conflicts in interest • Conflict over future CO2 emissions, developed and developing countries. • Developing countries projected to make up half of all CO2 emissions by 2035