ATMOSPHERE AND CLIMATE CHANGE

Environmental Science

I. Definitions A. Weather = state of the

atmosphere at a particular place at a particular moment

B. Climate = the long-term prevailing weather conditions at a particular place

based upon records taken

II. Factors that determine climate

A. Latitude – the distance from the equator measured in degrees north or south

1. the most important factor determining climate

2. the amount of solar energy an area of Earth receives depends on its latitude

3. Low Latitudes

A. More sun falls on this area than others

B. Night and day are both about 12 hours long throughout the year

C. Temperatures are high throughout the year

D. No distinct summer or winter

4. High Latitudes – regions closer to the poles

A. Sun is lower in the sky B. Sunlight hits Earth at an

oblique angle and spreads over a larger surface area than at the equator

C. Yearly average temperatures near the poles are lower than at the equator

d. Hours of daylight vary 1. 45 degrees north and south

latitude, there is 16 hours of daylight during the summer and 8 hours of sunlight during the winter

2. near the poles, sun sets for only a few hours each day in summer and rises for only a few hours during the winter

3. Creates a large yearly temperature range

B. Atmospheric Circulation 1. Three important properties

of air illustrate how air circulation affects climate

A. Cold air sinks because it is denser than warm air

1. as it sinks, it compresses and warms

B. Warm air rises 1. it expands and cools as it

rises

C. Warm air can hold more water vapor than cold air 1. when warm air cools, the

water vapor it contains may condense into liquid and form rain, snow or fog

2. Solar energy heats the ground which warms the air above it

3. warm air rise and cooler air moves in to replace it

4. Wind = the movement of air within the atmosphere created by the above (#2 and 3)

5. pattern of global atmospheric circulation results because Earth rotates and because different latitudes receive different amounts of solar energy

A. Circulation pattern determines Earth’s precipitation pattern

6. Global circulation patterns A. Cool normally sinks

1. over equator cool air cannot descend because hot air is rising below the cool air

2. the cool air is forced away from the equator and toward the poles

B. At 30 degrees N and S latitudes air begins to accumulate in the upper atmosphere

1. some of the air sinks back to the Earth’s surface and becomes warmer as it descends

2. warm, dry air moves across the surface causing water to evaporate from land below

3. Descending air either moves toward the equator or flows toward the poles

A. Air moving toward the poles warms while it is near Earth’s surface

C. At 60 degrees N and S latitude, this warmed air collides with cold air traveling from the poles

1. the warm air rises 2. a small part of this rising air

returns back to the circulation pattern between 60 and 30 degrees north and south latitudes

3. Most of the uplifted air is forced toward the poles

A. Cold, dry air descends at poles (very cold desert)

7. Prevailing Winds

Winds that blow predominately in one direction throughout the year

A. Do not blow directly northward or southward

1. Because of the rotation of the Earth

A. Winds are deflected to right in Northern Hemisphere

B. Winds are deflected to left in Southern Hemisphere

B. Trade winds – belts of prevailing winds in both hemispheres between 30 degrees north and south

1. blow from northeast in Northern Hemisphere

2. blow from southeast in Southern Hemisphere

C. Westerlies – prevailing winds produced between 30 and 60 degrees north and south latitudes

1. blow southwest in the Northern Hemisphere

2. blow northwest in the Southern Hemisphere

D. Polar easterlies

blow from the poles to 60 degrees north and south latitude

C. Oceanic Circulation Patterns

1. surface ocean currents have a great effect on climate because water holds large amount of heat

A. Movement of surface ocean currents is caused by winds and the rotation of the Earth

B. Surface currents redistribute warm and cool masses of water around the planet

C. Some surface currents warm or cool coastal areas year round

D. Affect the climate in many parts of the world

2. El Nino – Southern Oscillation

- the short term (6-18 month period) periodic change in the location of warm and cools water masses in the Pacific Ocean

A. Winds in the western Pacific which are usually weak, strengthen and push warm water

eastward

B. Rainfall follows and produces increased rainfall in southern US and in equatorial South America

C. Causes drought in Indonesia and Australia

d. La Nina – the water in the eastern Pacific is cooler than usual

E. El Nino and La Nina are opposite phases of the El Nino-Southern Oscillation (ENSO) cycle

1. El Nino is the warm phase

2. La Nina is the cool phase

3. Pacific Decadal Oscillation - a long-term (20-30 years)

change in the location of warm and cold water masses in the Pacific

A. PDO influences the climate in the northern Pacific Ocean and North America

B. Affects ocean surface temperatures, air temperatures,

and precipitation patterns

D. Topography

1. Elevation – height above sea level A. Temperatures fall about 11

degrees for every 1,000 m increase in elevation

2. Mountains and ranges also influence the distribution of precipitation

A. Rain shadow – one side of the mountain gets rain from the ocean air while the opposite side receives dry air

E. Other Influences

1. Solar maximum – the sun emits an increased amount of UV radiation

A. UV radiation produces more ozone

B. The increase in ozone warms the

atmosphere C. Increased solar radiation can also

warm the lower atmosphere and

surface of the Earth

2. Volcanic eruptions – cause sulfur dioxide gas to reach the upper atmosphere

A. The sulfur dioxide can remain in the atmosphere for up the 3 years

B. Reacts with smaller amounts of water vapor and dust in the atmosphere

C. This reaction forms a bright layer of haze that reflects enough sunlight to cause the global temperature to decrease

III. The Ozone Shield

A. Ozone layer – an area in the stratosphere where ozone is highly concentrated

1. ozone – molecule made of three oxygen molecules

2. ozone layer absorbs most of the ultraviolet (UV) light from the sun A. UV light can damage genetic material

in living organisms

B. Ozone Depletion

1. chloroflourocarbons (CFCs) – class of human-made chemicals; can damage ozone

A. Non-poisonous, nonflammable, and non-corrosive to metals

B. Used as coolants in refrigerators and air conditioners, in making plastic foams, and as propellants in spray cans

C. Are chemically stable at Earth’s surface

D. Break apart in stratosphere and absorb UV radiation which destroys ozone 1. each CF molecule contains one – four

chlorine atoms 2. a single chlorine atom can destroy

1,000,000 ozone molecules

2. ozone hole – a thinning of stratospheric ozone that occurs over the poles during the spring

A. First reported in 1985 above the South Pole 1. ozone had thinned 50-98%

B. NASA went back and looked at data from 1979 and discovered the first signs of zone thinning

C. Ozone thinning is also occurring over the Artic

D. in 1997, ozone levels over part of Canada were 45% below normal

3. How ozone holes form

A. Polar vortex – strong circulating winds over Antarctica during winter

1. isolates cold air from surrounding warmer air

2. air inside vortex grows extremely cold and fall below -80 degrees C

3. form polar stratospheric clouds – high altitude clouds made of water and nitric acid

B. On surface of polar stratospheric clouds, the products of CFCs are changed to chlorine

1. when sunlight returns in spring, chlorine is split into two chlorine atoms by UV rays

2. chlorine atoms rapidly destroy ozone

3. destruction of ozone causes a thin spot or ozone hole that lasts several months

A. Some estimate that 70% of ozone layer can be destroyed during this time

C. Ozone produced as air pollution does not repair the ozone hole

1. ozone produced by pollution breaks down or combines with other substances in troposphere before it can reach the stratosphere

4. Effects of ozone thinning on humans

A. More UV light reaches Earth’s surface which damages DNA

B. Makes body more susceptible to skin cancer

C. May cause other damaging effects to human body

5. Effects of ozone thinning on plants and animals A. Higher UV light can kill phytoplankton

1. disrupts ocean food chains 2. increases amount of CO2 in atmosphere

B. Higher UV light is damaging to amphibians

1. kills eggs which do not have shells 2. amphibians are indicator species –

species used to indicate environmental changes

C. Higher UV light can damage plants by interfering with photosynthesis

1. results in lower yield crops

6. Protecting the Ozone Layer A. Montreal Protocol of 1987

1. meeting of nations in Canada which agreed to take action against ozone depletion

2. agreed to limit the production of CFCs

B. A second Conference was held in Copenhagen, Denmark in 1992\

1. Developed countries agreed to eliminate most CFCs by 1995

2. US pledge to ban all substances that endanger the ozone layer by 2000

C. Chemical companies have developed CFC replacements

1. spray cans no longer use CFCs as propellants

2. air conditioners are becoming CFC free

D. There has been a decline in CFC production since Montreal Protocol

E. CFC molecules remain active in stratosphere for 60-120 years

1. CFC released 30 years ago are still destroying ozone today

2. it will be many years before the ozone layer recovers

IV. Global Warming

A. Greenhouse Effect - the process of heat absorption in

which sunlight streams through the atmosphere and heats the Earth

1. some of the heat escapes into space

2. some of the heat is absorbed by gases in the troposphere and warms the air

3. Greenhouse Gases – gases that absorb and radiate heat A. Water vapor B. Carbon dioxide C. Chlorofourocarbons D. Methane E. Nitrous oxide F. Water vapor and carbon dioxide

account for most of the absorption of heat that occurs in the atmosphere

B. Measuring carbon Dioxide in the Atmosphere 1. First measured in 1958 by

Charles David Keeling in Mauna Loa in Hawaii

A. 1st measurement was 314 parts per million of carbon dioxide in air or .0314%

1. levels fell and rose seasonally

B. By 2000 the average level of carbon dioxide was about 368 parts per million

1. in 42 years, carbon dioxide increased 54 parts per million

2. 17% increase 3. Largely due to burning of

fossil fuels

C. Greenhouse gases and Earth’s temperature 1. scientists believe that greenhouse gases trap heat near the Earth’s surface and increase the temperature

2. Comparisons of carbon dioxide and average global temperatures for past 400,000 years support this view

3. Today, we are releasing more carbon dioxide than another other greenhouse gas A. Results of power plants and vehicles B. We are also releasing CFCs, methane and nitrous oxide

D. Global Warming – predicted increase in global temperatures

1. Earth’s average global temperature increased in the 20th century

2. Most agree it will continue during 21st century

3. not all scientists agree that it is caused by greenhouse gases

A. Some believe that the warming is due to part of natural climatic variability

B. This type of fluctuations in temperature have occurred throughout time

E. Modeling Global Warming 1. scientist cannot make

accurate predictions about the rate of global warming

A. Climatic patterns are too complex

B. Too many variables

V. Consequences of a Warmer Earth A. Melting ice and rising sea

levels

1. would cause sea levels around world to rise

2. coastal areas may flood 3. people who live near coastline

would lose homes and sources of incomes

4. beaches are eroded 5. salinity of bays and

estuaries may increase and thus affect marine fisheries

6. coastal freshwater aquifers may become salty

B. Global Weather Patterns 1. oceans may absorb more heat, making hurricanes more common

2. may alter ocean currents

3. could affect weather patterns

C. Human Health Problems

1. Heat related deaths may increase

2. Increase in ground level ozone may cause more respiratory problems

3. warmer temperatures may enable insects, such as mosquitoes, to increase causing more disease

D. Agriculture

1. Extreme weather patterns may become more common affecting crops

E. Effects on Plants and Animals 1. could alter range of plant

species and change composition of plant communities

2. may cause shift in geographical range of some animals

3. warming tropical waters may affect coral reefs

VI. Reducing the Risk A. 1997, 160 countries met and

set time tables to reduce emissions of greenhouse gases

B. Kyoto Protocol – requires developed countries to decrease emissions of carbon dioxide and other greenhouse gases by an average of 5 % below their 1990 levels by 2012

C. US did not ratify treaty