Atmosphere and Climate Change

1
Atmosphere and Climate Change

• Chapter 13
• Environmental Science

2
What is Climate?

• Weather vs. Climate
• Weather state of the atmosphere at a particular
  place at a particular moment
• Day-to-day conditions of the atmosphere
• Climate the long-term prevailing weather
  conditions at a particular place based upon
  records taken
• Year-to-year average weather patterns

3
Climate

• In Seattle and Phoenix it may be raining, warm,
  or windy in both places. But their climates are
  quite different. Seattles climate is cool and
  moist, whereas Phoenixs climate is hot and dry

4
What determines climate?

• Determined by a host of factors
• Latitude
• Atmospheric circulation patterns
• Oceanic circulation patterns
• Geography
• Solar activity
• Volcanic activity
• Distance from the equator

5
Latitude

• Distance from the equator measured in degrees
  north or south of the equator
• Equator is located at 0o
• North pole 90o north
• South pole 90o south

6
(No Transcript)
7
Low Latitudes

• More solar energy falls on areas near equator
  than those closer to poles
• Solar energy is more highly concentrated
• Night and day are both 12 hours long year long
• Temps are high year-round
• No summers or winters

8
High latitudes

• Amount of energy received here is reduced
• Sun hits at an oblique angle which spreads over a
  larger surface area but is LESS concentrated than
  those rays found at the equator
• Low yearly average temps
• At 45o north and south latitude there can be as
  much as 16 hours of sunlight during the day in
  summer and as little as 8 hours of sunlight
  during the winter
• At the poles the sun sets for only a few hours
  each day during the summer and rises for only a
  few hours each day in the winter

http//youtu.be/ZZcafg-meJA
9
Atmospheric circulation

• 3 properties of air that affect climate
• Cold air sinks because it is more dense than warm
  air
• As it sinks it compreses and warms
• Warm air rises
• It expands and cools as it rises
• Warm air holds more water than cold air
• So when warm air cools precipitation is formed

10
wind

• Solar energy heats the surface and warms the air
  above
• This warm air rises and cool air replaces
• This movement causes the winds
• the earth rotates and different latitudes receive
  different levels of solar radiation causing a
  global wind pattern and determines the
  precipitation pattern as well

11
Hadley Cell

• The Hadley Cell involves air rising near the
  equator, flowing toward the North and South
  Poles, returning to the surface of the Earth in
  the subtropics, and flowing back toward the
  equator at the surface of the Earth. This
  produces winds called the trade winds and the
  tropical easterlies.

12
http//youtu.be/Ye45DGkqUkE
13
Prevailing winds

• Winds that blow predominantly in one direction
  throughout the year
• Are affected by the coriolis effect
• Trade winds, westerlies, and polar easterlies

14
Oceanic circulation patterns
15
El Nino Southern Oscillation

• Short-term (6-18 month) periodic change in
  location of warm and cold water masses in the
  Pacific ocean
• During El Nino, weak winds in the western pacific
  intensify and push warm water eastward
• La Nina is the opposite affect
• El Nino warm phase
• La Nina cold phase

http//youtu.be/7FVZrw7bk1w
16
Pacific Decadal Oscillation

• Long term, 20-30 year change in the location of
  warm/cold water masses in the Pacific ocean
• Influences climate in northern Pacific Ocean and
  North America
• Affects
• ocean surface temps
• Air temps
• Precipitation patterns

17
(No Transcript)
18
Topography

• Height above see level (elevation) affects temps
• Temps fall by 6oC (11oF) for every 1000m increase
• Can influence climate by affecting air/wind
  circulation and can affect precipitation

19
(No Transcript)
20
Other influences

• Both the sun and volcanoes have influenced the
  worlds climate
• Sun
• emits UV radiation, creates ozone and heats the
  stratosphere and can also heat the surface a
  little
• Volcanic eruptions
• in large scale may release enough SO2 into the
  upper atmosphere and reacts with water vapor and
  dust
• This reaction forms a bright layer of haze that
  reflects enoguh sunlight to decrease global temps

21
Seasonal changes
22
Ozone layer

• High concentration of O3 found in the
  stratosphere
• Absorbs most UV light from sun
• UV radiation is harmful and affects genetic
  material in cells
• Earths sunscreen

23
Ozone depletion

• During the 1970s scientists began to worry about
  CFCs (Chlorofluorocarbons) damaging the ozone
  layer
• Were popular in coolants found in refrigerators
  and air conditioners and propellants in spray
  cans
• CFCs are stable at surface but in the
  stratosphere they break down and these sub-parts
  destroy the ozone
• Each CFC contains 1-4 chlorine atoms
• 1 Cl atom can destroy 100,000 O3 molecules

24
(No Transcript)
25
The ozone hole

• In 1985 an article in Nature depicted the hole in
  the stratospheric ozone layer over the south pole
• Although O3 concentrations fluctuate throughout
  the year scientists went back through satellite
  data starting from 1978 and saw a growing opening

26
(No Transcript)
27
(No Transcript)
28
How does the ozone hole form?

• During the polar winter strong circulating winds
  called the polar vortex isolate cold air from
  surrounding warm air and becomes extremely cole
  with the vortex
• When temps fall below -80oC polar stratospheric
  clouds form (H2O Nitric Acid)
• Here, CFCs are converted to molecular chlorine
• In spring, sunlight splits these molecules into
  Cl atoms and they rapidly destroy O3

29
Why doesnt O3 pollution fix this?

• O3 is super reactive
• It will react and form other substances at the
  surface or in the troposphere long before it ever
  reaches the stratosphere

30
Effects of thin ozone layer

• Humans
• More UV radiation
• UV radiation affects and changes DNA
• Cataracts
• Can lead to higher levels of caner or other
  damaging effects to the body
• Weakened immune response

• Plants and animals
• More UV radiation
• Can kill single-celled organisms like
  phytoplankton
• Can disrupt food chains and increase CO2 in
  atmosphere
• Especially damaging to amphibians due to their
  nesting habits and lack of shells
• Can affect photosynthesis

31
Protecting the ozone layer

• 1987 an agreement called the Montreal Protocol
  was put in place to limit the use of CFCs
• Many nations have banned together to reduce or
  eliminate the use of CFCs
• Considered an international environmental success
  story by many people

32
Global Warming

• A result of increasing global avg. temps
• Has always fluctuated but the rate and the extent
  is most worrisome
• We ARE impacting this
• Global warming is mainly dependent upon the
  properties of the Greenhouse Effect

33
Greenhouse effect
34
Greenhouse Effect
35
Major greenhouse gases

• Water vapor
• CO2
• CFCs
• Methane
• Nitrous oxide
• Of these water vapor and CO2 absorb the most heat

36
Major GHG sources
F-gases
CO2
N2O
Methane
37
Measuring CO2 in the atmosphere

• Most CO2 released into the air is absorbed by
  plants and the oceans
• CO2 levels, because of this, vary seasonally
• Summer, plants use more CO2 for photosynthesis
  than is released during respiration lower
  levels of CO2
• Winter, dying grasses and fallen leaves decay and
  release the carbon that has been stored from
  summer higher levels of CO2

38
Rising CO2 levels

• CO2 levels have increased over 20 in less than
  50 years
• Largely due to burning of fossil fuels

http//www.youtube.com/watch?vvA7tfz3k_9Afeature
player_embedded
39
(No Transcript)
40
Global warming

• Average surface temps have increased during the
  twentieth century
• Rising at similar rate with greenhouse gas levels
• Temps are not rising at a constant rate or the
  same across the world
• Natural climatic variability is cannot be
  entirely ruled out
• Computer models are used to make predictions
  about global warming

41
Consequences of global warming

• In North America, tree swallows, Baltimore
  orioles, and robins are nesting 11 days earlier
  than they did 50 years ago
• In Britain, at least 200 species of plants are
  flowering up to 55 days earlier than they did 40
  years ago
• Changing weather patterns
• Melting Ice and rising sea levels
• Human health
• These changes are not uniform everywhere

42
Rising sea levels

• Melting ice is causing sea levels to rise
• Coastal areas could be flooded
• Enormous s of people live near the coast and
  would lose their homes and sources of income
• Beach erosion
• Salinity levels increasing in wetlands
• Coastal freshwater aquifers could become too salty

http//youtu.be/hHSuXCqUnj4
43
(No Transcript)
44
Global weather patterns

• Warming temps cause rise in ocean temp due to
  more heat absorption
• Could increase frequency and severity of
  hurricanes and typhoons
• Could change ocean currents (i.e. shut off the
  Gulf Stream)
• Sever flooding in some areas and major droughts
  in others