Ch 20 Global Warming Part one

Global Warming PLAY VIDEO

Core Case Study: Studying a Volcano to Understand Climate Change NASA scientist correctly predicted that the 1991 Philippines explosion would cool the average temperature of the earth by 0.5Co over a 15 month period and then return to normal by 1995. Figure 20-1

Core Case Study: Studying a Volcano to Understand Climate Change The NASA model was correct. The success convince scientists and policy makers that climate model projections should be taken seriously. Other climate models have shown that global temperatures are likely to rise several degrees during this century.

PAST CLIMATE AND THE GREENHOUSE EFFECT Over the past 900,000 years, the troposphere has experienced prolonged periods of global cooling and global warming. For the past 1,000 years, temperatures have remained fairly stable but began to rise during the last century.

PAST CLIMATE AND THE GREENHOUSE EFFECT Figure 20-2

Average temperature over past 900,000 years Average surface temperature (°C) Figure 20.2 Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration) Thousands of years ago Fig. 20-2a, p. 465

Average temperature over past 130 years Average surface temperature (°C) Figure 20.2 Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration) Year Fig. 20-2b, p. 465

Temperature change over past 22,000 years Agriculture established Temperature change (C°) End of last ice age Average temperature over past 10,000 years = 15°C (59°F) Figure 20.2 Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration) Years ago Fig. 20-2c, p. 465

Temperature change over past 1,000 years Temperature change (C°) Figure 20.2 Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration) Year Fig. 20-2d, p. 465

How Do We Know What Temperatures Were in the Past? Scientists analyze tiny air bubbles trapped in ice cores learn about past: troposphere composition. temperature trends. greenhouse gas concentrations. solar, snowfall, and forest fire activity. Figure 20-3

Ice Cores PLAY VIDEO

How Do We Know What Temperatures Were in the Past? In 2005, an ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years. Figure 20-4

Concentration of carbon dioxide in the atmosphere (ppm) Carbon dioxide Variation of temperature (C°) from current level Figure 20.4 Science: atmospheric carbon dioxide levels and global temperature. Estimated long-term variations in average global temperature of the atmosphere near the earth’s surface are graphed along with average troposphere CO2 levels over the past 160,000 years. The rough correlation between CO2 levels in the troposphere and temperature shown in these estimates based on ice core data suggests a connection between the two variables. In 2005, an ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years. QUESTION: What are the implications of these data on your lifestyle now and in the future? (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and Physics Institute at the University of Bern, Switzerland) Temperature change End of last ice age Thousands of years before present Fig. 20-4, p. 466

PLAY ANIMATION

The Natural Greenhouse Effect Three major factors shape the earth’s climate: The sun. Greenhouse effect that warms the earth’s lower troposphere and surface because of the presence of greenhouse gases. Oceans store CO2 and heat, evaporate and receive water, move stored heat to other parts of the world. Natural cooling process through water vapor in the troposphere (heat rises).

Major Greenhouse Gases The major greenhouse gases in the lower atmosphere are water vapor, carbon dioxide, methane, and nitrous oxide. These gases have always been present in the earth’s troposphere in varying concentrations. Fluctuations in these gases, plus changes in solar output are the major factors causing the changes in tropospheric temperature over the past 400,000 years.

CO2 Levels

Major Greenhouse Gases Increases in average concentrations of three greenhouse gases in the troposphere between 1860 and 2004, mostly due to fossil fuel burning, deforestation, and agriculture. Figure 20-5

Figure 20.5 Science: increases in average concentrations of three greenhouse gases—carbon dioxide, methane, and nitrous oxide—in the troposphere between 1860 and 2005, mostly because of fossil fuel burning, deforestation, and agriculture. The fluctuations in the CO2 curve (top) reflect seasonal changes in photosynthetic activity, which cause small differences between summer and winter concentrations of CO2. (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and World Resources Institute) Fig. 20-5a, p. 467

Figure 20.5 Science: increases in average concentrations of three greenhouse gases—carbon dioxide, methane, and nitrous oxide—in the troposphere between 1860 and 2005, mostly because of fossil fuel burning, deforestation, and agriculture. The fluctuations in the CO2 curve (top) reflect seasonal changes in photosynthetic activity, which cause small differences between summer and winter concentrations of CO2. (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and World Resources Institute) Fig. 20-5b, p. 467

Figure 20.5 Science: increases in average concentrations of three greenhouse gases—carbon dioxide, methane, and nitrous oxide—in the troposphere between 1860 and 2005, mostly because of fossil fuel burning, deforestation, and agriculture. The fluctuations in the CO2 curve (top) reflect seasonal changes in photosynthetic activity, which cause small differences between summer and winter concentrations of CO2. (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and World Resources Institute) Fig. 20-5c, p. 467