Download Atmosphere and Climate Change

Environmental Science
ATMOSPHERE AND CLIMATE
CHANGE
I.
Definitions
Weather = state of the atmosphere at
a particular place at a particular moment
 A.
 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.
 1.
Topography
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