Chapter 4

Question 1

What four gases compose the atmosphere?

Answer 1

Oxygen (21%), nitrogen (78%), carbon dioxide (0.04%), and rare and other gases (1%)

Question 2

What is dynamic equilibrium?

Answer 2

When natural processes are in a state of balance it will maintain the average composition of the atmosphere e.g. Photosynthesis and aerobic respiration balance each other out

Question 3

(1) How does the atmosphere support life ?

Answer 3

1. Gases for natural processes
   - atmosphere contains oxygen, nitrogen, carbon and hydrogen which are all needed to make biological molecules used by living organisms
2. Delaying the escape of infrared energy
   - much of visible light is absorbed, converted to heat, and then re-emitted at infrared energy. Atmospheric gases absorb this infrared energy and convert it to heat, increasing atmospheric temperatures. This then raises the temperature of earth by; 1) warm atmosphere emits infrared energy which is absorbed by earths surface and 2)warm atmosphere reduces heat loss by conduction from land and oceans
3. Ocean currents
   - winds blowing over oceans creates currents that distribute heat by carrying warm water from tropical areas to higher latitudes, such as the north Atlantic conveyor belt. These currents can also distribute dissolved nutrients.

Question 4

(2) how does the atmosphere support life ?

Answer 4

1) transport of water vapour
- winds transport water vapour to areas that would otherwise get little or no precipitation

2) heat distribution
- most of the energy from the sun that is absorbed in the earths surface is absorbed in tropical regions. The warm surface heats the atmosphere above and this heat is distributed to higher latitudes by warm winds such as the south westerly winds that bring heat to the UK from the Caribbean Sea.

3. Absorption of electromagnetic radiation from the sun
   - UV lights that passes through the atmosphere is prevented from reaching earths surface by the various forms of oxygen in the stratosphere (O,O2,O3). These form the ozone layer and absorb the UV light

Question 5

What does atmospheric pressure do

Answer 5

It controls the ease with which water molecules can evaporate and escape from the water surface.
If atmospheric pressure were lower there would be no liquid water on earth.

Question 6

Why is the structure of the atmosphere important ?

Answer 6

Altitude affects the composition and physical features of the atmosphere resulting in a series of layers.
Different layers include :
- troposphere (80% of gas in the atmosphere)
-stratosphere (99.9% of gas in the atmosphere)

Question 7

What are the energy processes in the atmosphere ?

Answer 7

-solar energy arriving at earth and the energy being radiates back into space are generally in a state of dynamic equilibrium
-wavelengths of electromagnetic radiation arriving are mainly, UV, visible light, and near infrared. The wavelengths of radiation leaving earth mainly involve long wavelength far infrared radiation
-this energy, and the processs it drives, control factors such as the climate, ocean currents and therefore the distribution of species
-any human actives that affect the movement of energy could affect any of these factors and thus the survival of living organisms

Question 8

What are human activities increasing the concentrations of ?

Answer 8

Increasing the concentrations of greenhospuse gases that absorb infrared radiation and warm the atmosphere

Question 9

What are the major anthropogenic sources of greenhouse gases and how do human activities increase the atmospheric concentration?

Answer 9

1) carbon dioxide
- combustion of fossil fuels and wood, ploughing of soils, drainage of marsh’s and bogs

2)methane
- anaerobic respiration by microbes in paid fields, landfill sites, and the intestines of livestock

3)Oxides if nitrogen
-oxygen and nitrogen in the air react at high temperatures in locations such as vehicle engines. They’re then released into the atmosphere in exhaust gases.

4)Chlorofluorocarbons (CFCs)
-CFCs were used as aerosol propellants, refrigerants, solvents,named in expanded foam plastics

5) tropospheric ozone
- produced by the photochemical breakdown of NO2 and subsequent reactions with oxygen

Question 10

What does the North Atlantic conveyor (the Gulf Stream) involve ?

Answer 10

The North Atlantic conveyor involves the movement of layers of surface and deep water in the North Atlantic Ocean which distribute heat energy and control the climate
Warm water from the tropical Atlantic Ocean travels north eastwards towards north west Europe. Two processes drive this movement:
1) friction with the prevailing winds blowing over the ocean surface from the south west to the north east causes surface water to flow in the same direction
2) water in the north east Atlantic sinks as it cools and becomes denser, drawing water in to replace it.
-UK is warmed by this conveyor belt which brings water from tropical regions

Question 11

What changes in the North Atlantic conveyor are caused by global warming?

Answer 11

-Higher atmospheric temperatures cause land ice on Greenland to melt and flow into the sea
- it dilutes the seawater causes salt concentration to go down. This less saline water is less dense than normal seawater so it’s less likely to sink
-this reduces the flow rate of the water current which could cause NW Europe to be older

Question 12

What is el niño?

Answer 12

• it occurs typically every 2-7 years
• normal conditions: trade winds blow west across the Pacific Ocean near the equator so ocean currents flow in the same direction
• it causes deep cold water to be drawn upwards near the coast of South America. This water is rich in nutrients and causes algae blooms. These blooms feed a rich food web, which is important for commercial fisheries which provide food for local human population.
  -current continues to move west and becomes warmer as it travels towards the east coast of Australia
• current also affects rainfall patterns as warm water causes more precipitation

-during El Niño this is the opposite: the trade winds blow east across the pacific instead. This means that the rich food web in South America collapses as nutrient upwelling stops
-rainfall in eastern Australia is reduced while coastal parts of South America which are normally deserts may have heavy rain and floods.

Question 13

What are some of the global impacts of El Niño?

Answer 13

-droughts in NE Africa, S Africa, and China
-fewer hurricanes in the North Atlantic
- fewer tropical cyclones in Japan

Question 14

What is La Niña?

Answer 14

La Niña occurs when the trade winds blow more strongly in the normal direction, so water currents speed up and temperature differences between the western and eastern pacific and increased

Question 15

What are the two reasons that rising temperatures cause an increase in sea level?

Answer 15

1) thermal expansion of sea water
- the warmer atmosphere heats the seawater which therefore expands, causing sea levels to rise
-however, only the water at the surface can be heated by direct contact with the atmosphere, so cold deep water can only be heated when the slow ocEan currents bring it to the surface

2) melting land ice
- as the earth warms up ice will melt. Ice that is floating on the sea surface does not cause sea levels to rise when it melts as it occupies the same volume as the volume of ice that was below water level
-however ice that is on land will cause sea levels to rise as the water flowing into the sea increases its volume

Question 16

What are the changes in cryopshere

Answer 16

(A3 sheet for full explanations)
1) reduced snow cover
2)glaciers: changes in extent and speed of movement
3)changes in ice thickness and area
4) loss of ice shelves

Question 17

How does more heat in the atmosphere cause changes in rainfall?

Answer 17

-increased temperatures cause more evaporation, which causes more precipitation either in the same area or somewhere else
-which higher temperatures, the air may have to move further towards a cold area before the water vapour cools enough to condense and fall as either rain or snow
-changes in wind direction and velocity may also affect precipitation by carrying the humid air to new areas causing increased rainfall in one area but reduced rainfall in another.

Question 18

How does more heat in the atmosphere cause changes in wind pattern?

Answer 18

-jet streams are strong winds that blow from west to east along a meandering path in the upper troposphere
-they’re caused by difference in temerpatures and density between two air masses such as warm air in mid latitudes and cold air in polar regions
-rotation of the earth creates a Coriolis force which causes winds to blow in a spiral fashion
-the jet streams control the movement of air bodies that create rain which as the cyclonic storms that are carried across the Atlantic to the UK.

Question 19

What are negative feedback loops?

Answer 19

-they reduce the size of the original change
-takes place when environmental changes cause other changes which decreases the rate of the initial change. It reduces its effects and helps it to re establish the original equilibrium
- for example:
1) increased low level clouds
- higher temperatures increase evaporation, leads to increased condensation and produces more clouds. Clouds have a high albedo so more sunlight is reflected away and the amount of warming is reduced

2)increased photosynthesis
-higher temperatures increase rate of photosynthesis which removes more carbon dioxide from the atmosphere. This CO2 is stored in trees so CO2 levels decrease in the atmosphere and therefore warming is reduced.

Question 20

What are positive feedback loops?

Answer 20

-positive feedback loops increase the size of the original change
-it takes place when an environmental change causes other changes which increases the rate of the initial change or level of impact.
-examples include:

1) melting permafrost
-warming causes melting of permafrost which releases methane gas and causes further warming

2)ocean acidification
-carbon dioxide in the atmosphere dissolves into oceans, producing carbonic acid and making oceans more acidic. This reduces coral survival and therefore reduces carbon sequestration as no carbon can be stored as calcium carbonate so more carbon is left in the atmosphere.

3)ice and snow melt
-warming reduces area of snow and ice, more sunlight is absorbed by earth surface as there’s less albedo effect, this causes further warming

Question 21

What are tipping points?

Answer 21

-A tipping point is reached when the changes caused by human activities cause further changes such that the human activities are no longer needed to maintain the changes.

Question 22

What are the effects UV-B has on living organisms?

Answer 22

-if UVB is not absorbed in the atmosphere then it will reach the Earth’s surface and may be absorbed and some is converted to chemical energy as it breaks up biological molecules causeing skin damage, DNA damage, skin cancer, leaf Tudeh damage and reduced photosynthesis

Question 23

How can evidence on ozone depletion be collected ?

Answer 23

1) ground based data collection
- first evidence of ozone depletion was collected by the British Antarctic survey at Halley station in Antarctica. The detection of higher levels of UV at ground level was evidence of this ozone depletion

2) satellite surveys
- satellites orbit the earth at greater altitudes then the stratosphere so UV passing down through the stratosphere cannot be measured. However, UV light reflected by the earth were higher suggesting ozone levels were reduced

3) air samples from the stratosphere
- air samples collected by helium gallons and high flying research air crafts can confirm the chemicals cause depletion

4) variability in ozone levels
- the concentration of ozone varies between different areas, at different times, at different altitudes.

Question 24

What is the Rowland-Molina hypothesis?

Answer 24

-In 1974 two American science suggested that the chemical properties of CFCs could lead to ozone depletion in the stratosphere.
-their theory was based on the chemical behaviour of CFCs:

1) persistence
-CFCs are chemically stable so they remain in the atmosphere long enough to be carried up to the stratosphere

2) dissociations by UV
-CFCs are stable in the troposphere, but not stratosphere as they’re exposed to higher levels of UV. They absorb the UV which breaks down carbon to chlorine bonds and releases chlorine free radicals

3) reactions of chlorine with ozone
- chlorine reacts with monatomic oxygen preventing its reaction with O2 to form O3. Further reactions prevent the formation of more ozone molecules

Question 25

Ozone depletion over Antarctica

Answer 25

-stratospheric temperatures over Antarctica are lower than anywhere else on earth, allowing the formation of stratospheric clouds and ice crystals
-these provide surfaces on which chemical reactions take place, producing chlorine molecules from the chlorine released from CFCs
-winds around Antarctica rotate to create a polar vortex, which little mixing between the air over Antarctica and the rest of the atmosphere
-this maintains low temperatures and produces higher concentrations of the chlorine that forms on the ice crystals
-it is completely dark in the Antarctic over winter. When spring arrives, sunlight splits the chlorine molecules which produce the chlorine free radicals that cause ozone depletion

Question 26

What is the Vienna convention (1985)

Answer 26

-this produces an agreement between every country in the UN to protect the ozone layer but included no legally binding goals

Question 27

What is the Montreal protocol?

Answer 27

The mains aspects were:
-the manufacture and use of CFCs and other ozone depleting substances (ODS) would be phased out and then banned
-use of HCFCs will be phased out by 2030

The success of the Montreal protocol had several causes:
- international recognition of the serious consequence of ozone depletion
- agreement between nearly every country that action must take place