1. Chapter 13: Atmosphere & Climate Change 13-1 Climate & Climate Change
Weather: state of the atmosphere at a particular place at a particular moment
Climate: long-term prevailing weather conditions at a particular place (based on records)

2. Climate is determined by:
1) Latitude: distance north or south of the equator
Low latitudes = direct sunlight = concentrated on a smaller surface = warmer
High Latitudes = indirect sunlight (at an angle) = spread over a larger surface = colder

3. Climate is determined by:
2) Atmospheric Circulation
cold air sinks (denser) – it compresses and warms
warm air rises – it expands and cools
warm air holds more water than cold air (forms rain, snow, fog when it cools)
wind: movement of air within the atmosphere

4. Atmospheric Circulation (cont.)
Determines Earth’s precipitation pattern
Cool air over the equator cannot sink because hot air is rising below – it rises and is forced toward the poles
It accumulates and sinks at about 30° north & south
Warming air moves across the land toward the equator or toward the poles
Cold air from the poles collides with this warm air at about 60° N & S
Prevailing Winds: winds that blow predominantly in one direction throughout the year
Trade winds: belts of prevailing winds (produced in both hemispheres)

5. Climate is determined by:
3) Oceanic Circulation Patterns
Ocean currents have a great effect on climate because water holds lots of heat
Caused mostly by winds & Earth’s rotation
Currents That Change Their Pattern of Circulation over Time:
El Niño: short-term (6-18 mos.) change in the location of warm & cold water masses in the Pacific ocean
Winds strengthen and push warm water eastward
Increases rainfall in the southern ½ of the U.S.
La Niña: the cold phase of the cycle – water in the eastern Pacific is cooler than usual

6. Climate is determined by:
4) Topography
Altitude: temperature decreases as elevation increases
Rain Shadow Effect
as air moves across a mountain range it rises, cools, and drops the water it is carrying
dry air descends, warms, and draws up moisture creating an dry area with little rainfall

7. Seasonal Changes In Climate
Because of the Earth’s tilt, the angle at which the sun’s rays strike the Earth changes as the Earth orbits the sun.
This change in angle creates the seasons.

8. 13-2 The Ozone Shield Ozone: 3 oxygen atoms
Ozone layer: highly concentrated area of ozone in the stratosphere
Absorbs most of the ultraviolet UV light from the sun
“Sunscreen”
UV light harms organisms by damaging DNA in cells
Chemicals That Cause Ozone Depletion
Chlorofluorocarbons (CFCs): man-made, used as coolants in refrigerators and AC, used as propellant in spray cans
O3 + CFCs  O2

9. Satellite Images of the ozone hole (purple).
The Ozone Hole: a thinning of the ozone layer that occurs over the poles during spring
Why doesn’t “bad” ozone (ozone pollution) repair it? Ozone produced by pollution breaks down before it can reach the stratosphere.
Satellite Images of the ozone hole (purple).

10. Damaging Effects of UV Light
Humans
Increased incidence of skin cancer
Premature aging of the skin
Increased incidence of cataracts
Weakened immune response
Amphibians
Death of eggs
Genetic mutations among survivors
Reduction of populations
Marine Life
Death of phytoplankton in surface water
Disruption in food chain
Reduction in the # of photosynthesizers
Land Plants
Interference with photosynthesis
Reduced crop yields

11. Ozone Help! The Montreal Protocol (1987)
An Environmental Success Story!
Group of nations agreed to limit CFC production
Eliminate most CFCs by 1995
U.S. banned all by 2000
Chemical companies developed CFC replacements
The battle isn’t over CFCs remain active in the stratosphere for yrs.

12. 13-3 Global Warming
Greenhouse Effect: Earth’s atmosphere acts like the glass in a greenhouse
Sunlight heats the earth’s surface
short wavelength radiation from the sun (UV and Visible light)
Heat radiates back up as long wavelength radiation (infrared)
Some escapes into space
Some is absorbed by gases in the troposphere, warming the air

14. Greenhouse Gases: gases that absorb and radiate heat
Millions of tons of CO2 are released annually from coal burning power plants, gas burning cars, trees burned to clear forests for farming, etc.
More greenhouse gasses = increased global temperature
*Without the greenhouse effect Earth would be too cold for life.*
Major Greenhouse Gases and Their Sources
Carbon Dioxide, CO2: burning fossil fuels & deforestation
Water Vapor, H2O: evaporation, plant respiration
Methane, CH4: animal waste, biomass burning, fossil fuels, landfills, livestock, rice paddies, sewage, wetlands
Nitrous Oxide, N2O: biomass burning, deforestation, burning of fossil fuels
Chlorofluorocarbons (CFCs): refrigerants, aerosols, foams, propellants, solvents

15. Global Warming: increase in global average temperature

16. Discovering long-term trends in atmospheric CO2
Ice is laid down in layers, year-after-year. As such, it preserves a record of environmental conditions at the time of deposition. Scientists search this ice for clues about the Earth's past environments.
Source:

17. Ancient Air is trapped in the ice. Scientists drill for it.
Scientists dig in the ice for clues about the chemical composition of ancient atmospheres. Tiny bubbles in Antarctic ice store remnants of ancient atmospheres. Scientists extract ice cores, determine their age, then crush them in a vacuum. Liberated air from bubbles is sampled for gas composition.
Source:

18. Bubbles in a section of ice from an ice core
Bubbles in a section of ice from an ice core. The bubbles are filled with air from an ancient atmosphere. Scientists crush the ice in a vacuum. The freed air is analyzed for the ancient mix of atmospheric gases.
Source:

19. National Ice Core Laboratory, University of Nevada, Reno.
Source:

24. Natural Causes
Natural climatic variability does occur. Widespread fluctuations in temperature have occurred throughout geologic time.

25. The Consequences of a Warmer Earth
1. Melting Ice and Rising Sea Levels
Amt. of ice and snow at the poles would decrease
Sea lvls. Would rise
Coastal wetlands and low-lying areas might be flooded
People who live near coastlines could lose their homes & sources of income
Beaches could be extensively eroded
Salinity of bays and estuaries might increase – negatively affecting marine fisheries
Coastal freshwater aquifers could become too salty to be sources of freshwater

26. The Consequences of a Warmer Earth
2. Global Weather Patterns
Surface of the oceans will absorb more heat
May make hurricanes and typhoons stronger
Cause a change in ocean current patterns – could significantly affect the world’s weather
Some regions might have more rainfall than normal, while other regions have less
Severe flooding in some places while others have devastating drought.

27. The Consequences of a Warmer Earth
3. Human Health Problems
Increased heat-related deaths
Concentrations of ground-level ozone could increase
Respiratory illnesses would increase, especially in urban areas
Insectborne diseases could spread (might enable mosquitoes, which carry diseases such as malaria to greatly increase in number

28. The Consequences of a Warmer Earth
4. Agriculture
Extreme weather events (like droughts) could become more frequent
Higher temps. could = decreased crop yields
Irrigation demands would increase (further depleting aquifers)

29. The Consequences of a Warmer Earth
5. Effects On Plants and Animals
Could alter the range of plant species and could change the composition of plant communities
Trees could colonize northward into cooler areas – forests would shrink in the southern part of the range and lose biodiversity
May shift geographical range of some animals
i.e. birds may not have to migrate as far south during winter
warming in the surface waters of the ocean might cause a reduction of zooplankton (tiny shrimplike animals that many marine animals depend on for food)
May kill the microscopic algae that nourish corals destroying coral reefs

30. Recent Findings The Intergovernmental Panel on Climate Change (IPCC)
a network of approx. 2,500 of the world’s leading climatologists from 70 countries
Predicted that human influences will continue to change the composition of the Earth’s atmosphere and continue to warm the Earth throughout the 21st century.
Reducing the Risk
The Kyoto Protocol
Required developed countries to decrease emissions of CO2 and other greenhouse gases by an average of 5 percent below their 1990 levels by 2012
In march 2001 the US and Australia decided not to ratify the Kyoto Protoco

31. Summary of Global Warming
Global Warming: an increase in global temperature caused by increased levels of greenhouse gases (the Greenhouse Effect) – could lead to climate change, melting of polar ice-caps -->rising sea levels
 Greenhouse Gases (carbon dioxide CO2 & others) warm the atmosphere by trapping heat
 Humans are producing greenhouse gases at a rapid rate by BURNING FOSSIL FUELS
 Solutions: decrease greenhouse gas production – car pool, walk, alternative energy sources (solar, wind, etc.)