Understanding the Earth's Atmosphere and Climate

1. Chapter 23 The Atmosphere, Climate, and Global Warming

2. The Atmosphere • Thin layer of gases that surrounds the Earth • Several layers - different temperatures, pressures, and composition • Atmosphere at sea level more dense due to Earth’s gravity pulling on gas molecules • Atmospheric pressure decreases with higher altitude as gas molecules less dense at higher altitudes NASA atmosphere animation from NASA/Goddard Space Flight Center Conceptual Image Lab and from PBS Atmosphere Layers

3. Troposphere: Life Giver and Weather Breeder • Innermost layer of Earth’s atmosphere, closest to Earth’s surface; about 17 km (11 mi) above sea level at equator and 8 km (5 mi) above over poles • 75-85% of Earth’s air mass • Composition: 78% Nitrogen; 21% Oxygen; Water vapor (0.01% frozen poles to 4% humid tropics); 0.93% Argon; 0.038% CO2; traces of dust, soot, methane (CH4), ozone (O3), and nitrous oxide (N2O). • Involved in chemical cycling of many of Earth’s vital nutrients • Winds and turbulent air currents here as responsible for our short-term weather and long-term climate. Animation

4. Stratosphere: Our Global Sunscreen • 2nd layer of Earth’s atmosphere; extends from about 17-48 km (11 to 30 miles) above Earth’s surface • Similar composition to troposphere except has 1/1000th the amount of water vapor and much higher ozone (O3) concentration • Ozone layer 17-30 km above sea level produced when oxygen interacts with UV radiation, keeps 95% of sun’s harmful UV from reaching us. Ozone animation • Allows life to exist on Earth: Protects us from sunburn, skin and eye cancer, cataracts, immune system damage. Prevents much of oxygen in troposphere from being converted to photochemical ozone, a harmful air pollutant. Photochemical smog video – sound is low but slides good

6. Atmospheric Circulation • Atmospheric circulation produces weather and climates • Global Atmospheric Circulation Animation • Coriolis Effect impacts atmospheric circulation • Coriolis Effect

7. Climate • Climate: • the representative or characteristic atmospheric conditions for a region on Earth over long periods of time • Important because similar climates support similar ecosystems (Biogeography Ch 7); useful in predicting types of organisms who do or could survive there • Microclimate • The climate of a very small local area, could even be as specific as beneath a tree

8. World Climates and Major Climate Types Based on Precipitation and Temperature

9. Climatic Change • Major climatic changes have occurred during the past 2 million years, temperatures fluctuating by several degrees Celsius • Appearances and retreats of glaciers • During the past 100 years, the mean global annual temperature has increased by 0.5 degrees Celsius • Not yet clear whether our current warm climate marks end of the ice ages or is merely an interglacial period with another glacial age due

15. Oceanic Conveyor Belt Red = warm surface water, transported westward and northward to Greenland Blue = water cools after contact with cold Canadian air, cold and salty (more dense) water sinks, flows south then east to Pacific, upwelling occurs in North Pacific Masses of sinking and upwelling waters balance Heat released to atmosphere from warm water keeps northern Europe warmer than if conveyor belt were not present

16. Tools for Studying Global Change • Evaluation of Geologic record • Real-Time Monitoring • Mathematical Models (GCM’s)

17. Average Concentration of Atmospheric Carbon Dioxide 1500-2000 Based on Geological Record of Glacial Ice Cores

18. Real-Time Monitoring • Monitoring is regaular collection of data for specific purposes • Collect data to provide baseline conditions to evaluate changes in future • See p. 500 “Monitoring of Atmospheric Carbon Dioxide Concentrations” at Mauna Loa Observatory

19. GCM – Global Circulation Model • Goal is to predict atmospheric changes on a global scale • Earth’s surface divided into large cells; uses several layers of data and mathematical calculations using supercomputers to make predictions of future change • May not be accurate predictions, but a good starting point: helps pinpoint what other data may be needed to predict future changes. Good at predicting what areas may be wetter or drier if certain atmospheric changes occur A – B is a few km in elevation E – C is a few hundred km in longitude C – D is a few 100 km in latitude

20. Global Warming • A natural or human induced increase in the average global temperature of the atmosphere near the earth’s surface • 4 factors • Amount of sunlight Earth receives • Amount of sunlight Earth reflects • Retention of heat by atmosphere • Evaporation and condensation of water vapor • BBC’s guide to climate change animations

21. Electromagnetic Radiation and Earth’s Energy Balance • Electromagnetic spectrum • The collection of all possible wavelengths of electromagnetic energy, considered a continuous range • the ones we are most concerned with in greenhouse effect: visible, UV (from sun’s radiation), infrared (heat). We can’t see UV or infrared. Much infrared is emitted by organisms as by-products of biological processes as waste heat • Infrared radiation and greenhouse effect link

22. Earth’s Energy Balance 30% incoming solar radiation reflected immediately in atmosphere by clouds and Earth’s surface. Of 70% remaining: 25% absorbed in upper atmosphere, 45% absorbed at Earth’s surface by plants, soil, rocks, water, etc. Some gets transformed to heat (infrared radiation) and radiates into space, while some is reabsorbed by greenhouse gases (eventually goes to space as well). About 2/3rd’s of incoming solar radiation is available to drive processes at or near Earth’s surface, including winds, hydrologic cycle Page 502, Fig 23.10

23. The Greenhouse Effect • Greenhouse Effect • The process of trapping heat in the atmosphere • Water vapor and several other gases warm the Earth’s atmosphere because they absorb and emit radiation • Greenhouse Gases • Gases that have a greenhouse effect • Water vapor, carbon dioxide, methane, CFCs (chlorofluorocarbons - aka freons – from AC, aerosol propellants – banned but still a problem from lingering and landfills – also known for stratospheric ozone destruction )

24. Emission of Energy From Sun vs. Earth

25. Greenhouse Effect

26. Global Warming • Negative and Positive feedback cycles affect the atmosphere • Increase in emission of greenhouse gasses • Solar Forcing, Natural Cycles, Aerosols (global dimming), Volcanic Eruptions, El Nino

27. Albedo Effect • Albedo refers to the reflectivity of a surface • Surfaces with high albedo, such as ice and snow, reflect great deal of sun’s radiation back into atmosphere – allowing surface to stay cooler. Surfaces without snow and ice absorbs more heat – allows surface to get warmer

28. High Correlation Between Temperature and CO2 as seen from evidence gathered in Antartica

29. Negative Feedback (1-4 top) and Positive Feedback (5-7 bottom) Cycles • Negative = cooler Earth due to: 1) algae growth 2) terrestrial vegetation growth 3) more precipitation in polar regions due to warm air = more snowpack and ice 4) water vapor evaporation = more clouds = more solar radiation reflected • Positive = warmer Earth due to 5) water vapor trapping heat in greenhouse effect 6) permafrost melting releases methane, another greenhouse gas 7) results in additional warming so 8) urban areas use more AC, burn more fossil fuels, releasing more CO2 = more warming

30. Feedback Effects • discusses feedback effects, cloud formation, and possible CO2 reduction methods, as well as government involvement, legislation, treaties Basics of climate feedback loops and detailed info on atmospheric feedbacks

31. Global temperature change during past 1000 years taking anthropogenic forcing from greenhouse gases into account but after solar and volcanic forcing removed

32. Effects of Global Warming • Changes in climatic patterns • Rise in sea level • Changes in biosphere

33. Projected change in annual temperatures to 2050 (top) Projected change in annual precipitation to 2050(bottom)

34. Adjustments to Global Warming • Mitigate warming through reduction of greenhouse gasses • Energy conservation • Alternative energy sources • Danger: rapid climatic change

35. Exponential Growth of sea-level rise, temperature stabilization and CO2 stabilization predicted after peak CO2 emissions are reached in 50-100 years

36. El Nino • Normal upwellings of deep ocean waters in Eastern Pacific are disrupted. Upwellings normally release CO2 to atmosphere as deep CO2-rich ocean waters reach surface. El Nino reduces CO2 outgassing so CO2 cycle affected. This affects weather patterns. oceanRead in text and watch this video link: • El Nino Animation • El Nino Information

37. Urban Dust Dome • Polluted urban air produced by the combination of lingering air and abundance of particulates and other pollutants in the urban air mass; holds the heat due to thermal inversion – see animation on one of the first slide animations in this Powerpoint of city next to mountain range. Relates between this chapter and the next one – heat plus air pollution