Global climate - natural greenhouse effect + natural variations in solar radiation

Question 1

What does the natural greenhouse effect do?

Answer 1

• Regulates Earth’s climate
• Keeps Earth’s surface at 15 degrees C average (ideal for life)
  
  • which would otherwise be 33 degrees C lower (-18 degrees C = impossible for life)

Question 2

How long has the natural greenhouse effect been taking place? and what causes it?

Answer 2

Caused by greenhouse gases
- A natural process that has always been present + predates human activity on Earth

Question 3

What are greenhouse gases and examples of them?

Answer 3

They occur naturally in Earth’s atmosphere
Include:
- Methane
- Carbon dioxide
- Water vapour
- Nitrous oxide

Question 4

How do greenhouse gases work?

Answer 4

Allow solar radiation to pass through/into the atmosphere - but then trap the heat like a ‘blanket’
- UV shortwave radiation passes through, but they absorb (trap) long-wave infrared radiation
- this infrared radiation is then re-radiated/ re-emitted by the Earth (heat energy).

Question 5

What are the stages of the natural greenhouse effect?

Answer 5

1. Short-wave radiation passes through atmosphere
2. Some short-wave radiation is absorbed and is converted into long-wave radiation
3. Some long-wave radiation passes back into space
4. Some long-wave radiation is reflected off greenhouse gases back to Earth, heating Earth up

Question 6

What kind of energy system does our atmosphere have?

Answer 6

The atmosphere is an open energy system, receiving energy from the sun
- Energy can enter and leave the atmosphere

• Inputs: insolation (solar radiation)
• Outputs: re-radiation

Question 7

How much energy is lost to space through reflection?

Answer 7

31% (other 69% is lost later on)

Question 8

How much energy is absorbed at the surface (which is then later lost to space)?

Answer 8

46%

Question 9

Why is the Earth’s solar budget due natural conditions?

Answer 9

It’s a balanced system
- Radiation Input = Radiation output
(the Earth is neither heating nor cooling)

Question 10

Where on Earth is the most solar energy received?

Answer 10

Most solar energy is received at the equator

Question 11

Where is the least solar energy absorbed?

Answer 11

At the equators

Question 12

What are the reasons for the Earth’s energy balance (places on Earth where more energy is absorbed than other areas)?

Answer 12

• Effect of latitude on insolation
• Seasons affecting amount of insolation
• Effect of cloud cover on insolation

Question 13

What is the effect of latitude on insolation?

Answer 13

• Sun’s energy = more concentrated at equator than poles, where it spreads over larger area (less heat per km^2 at poles)
• Sun’s energy travels through more atmosphere at poles + more energy absorbed by dust and pollen particles before it reaches surface
• Angle of the sun is lower in the sky at the poles + more energy reflected into space
• Snow + ice at poles also reflects more insolation than the land and sea at the equator

Question 14

How do warm and cold currents redistribute energy around Earth?

Answer 14

• Warm water moves from equator to poles
• Cold water moves from the poles towards the equator

Question 15

Why does the UK experience milder winters than expected?

Answer 15

For its latitude, winters should be colder, but due to the warming influence of the North Atlantic Drift, the winters are much milder than expected

Question 16

How do seasons also affect the amount of solar radiation (insolation) reaching different parts of the Earth?

Answer 16

Spring Equinox - 21 March
Winter Solstice - 21 December
Autumn Equinox - 23 September
Summer Solstice - 21 June

• This is because of the tilt of the Earth’s axis in relation to the sun

Question 17

How is the effect of insolation reaching Earth affected by seasons exampled in the month of December?

Answer 17

• Northern hemisphere is tilted away from the sun
• Further north from the equator, days are shorter, less insolation received (e.g. UK)
• Southern hemisphere is tilted towards the sun
• Further south from the equator, days are longer, more insolation receiver (e.g. Australia)

Question 18

What is the effect of cloud cover on insolation in Earth?

Answer 18

Stratocumulous clouds
- Less cloud cover = more insolation reaches
Earth’s surface

Question 19

How long are the natural changes in the amount of solar radiation reaching the Earth?

Answer 19

Occur over different timescales (temporal patterns):
- Short-term (rapid - over years / decades)
or
- Long-term (slow - over centuries / millenia)

Question 20

What is the main example of long-term, natural variation in solar radiation + climate / temperature?

Answer 20

The glacial - interglacial cycle

Question 21

For how long have there been a series of Glacials + Interglacials?

Answer 21

Over the last 2 million years

Question 22

What are Glacial periods?

Answer 22

Relatively cool periods
100,000 years

Question 23

What are Inter-glacial periods?

Answer 23

Relatively warm periods
10,000 - 10,000 years

Question 24

What is our present Inter-glacial period called, and how long has it lasted?

Answer 24

The Holocene started around 12,000 years ago

Question 25

What provides us with evidence of these glacial/inter-glacial periods and how long they’ve lasted?

Answer 25

The Vostok Ice Core, Antarctica
- Evidence can be seen in the CO2 levels in the Vostok Ice Core
- provides over 400,000 years of climate data

Question 26

What is the difference in the amount of ice present in glacial vs inter-glacial periods?

Answer 26

Earth in the Devensian Glacial:
- Cooler = more ice
Earth in the Holocene inter-glacial (now):
- Warmer = less ice

Question 27

Why does Earth experience glacial and inter-glacial periods?

Answer 27

Because Earth’s orbit around the sun varies:
- from circular to elliptical

Question 28

Why does Earth’s orbit vary from elliptical to circular?

Answer 28

Because of the gravitational pull from other planets

Question 29

What are Milankovich cycles?

Answer 29

The changes in the Earth’s orbit affecting the amount of solar radiation heating Earth’s surface, and therefore Earth’s temperature:
- Elliptical = cooler = glacial
- Circular = warmer = inter-glacial

Question 30

How long do Milankovich cycles last?

Answer 30

The cycle from elliptical orbit to circular completes every 100,000 years

Question 31

What is stage one of the Milankovich cycle?

Answer 31

A change - elliptical orbit - in the Earth’s orbit kick starts the process of long-term climate change
- Less insolation
- Climate 0.5 degrees C cooler

Question 32

What is stage two of the Milankovich cycle?

Answer 32

The Albedo effect takes over, exaggerating the effect, causing temperatures to fall further and a glacial to occur
- more white snow + ice
- Earth’s albedo (reflectivity) increases
- More insolation reflected into space
- Climate 5 degrees C cooler ( = glacial)

Question 33

How is the process then reversed after the first two stages?

Answer 33

Reversed by a return to circular orbit
- more insolation
- climate 0.5 degrees C warmer

• less white snow + ice
• Earth’s albedo decreases
• less insolation reflected into space
• climate 5 degrees C warmer ( = inter-glacial)

Question 34

How does the albedo effect affect the Milankovich cycle?

Answer 34

It amplifies the Milankovich cycle / glacial - inter-glacial cycle

Question 35

When does the surface of the Earth absorb more heat?

Answer 35

When a surface doesn’t have snow or ice it absorbs more heat

Question 36

What does a low albedo cause?

Answer 36

• 30% of insolation is reflected with low albedo
• low albedo = inter-glacial

Question 37

What does a high albedo mean?

Answer 37

• 90% of insolation is reflected with high albedo
• high albedo = glacial

Question 38

What evidence is there for the glacial cycle in Britain?

Answer 38

• When ice melted in Yorkshire about 2,000 years ago -> cargo of rocks was dumped miles away from home
  
  • These rocks were picked up by the glaciers + moved until the glacier melted
  • these out-of-place rocks are called erratics
• Glaciers shaped everything in their path - gouged out some of the most spectacular landscapes in Britain

Question 39

What evidence is there for the inter-glacial cycle in Britain?

Answer 39

• Most of last 2 million years - Ice Age was cold, but..
  
  • In London in 1930, builders dug up a collection
    exotic bones
    
    • e.g. one bone is 120,000 years old (which
      would place it in the middle of an ice age
    • however it does not belong to a wooly
      mammoth or polar bear
    • Instead it’s the tooth of a hippopotamus
  • This proves that the Ice Age was punctuated by
    warmer periods (some even warmer than today)
    
    • proves that right in the middle of London,
      120,000 years ago, icy wilderness was replaced
      by Serengeti plains
• Glaciers –> Swamps
• Mammoths –> Hippos

Question 40

What are examples of natural short-term changes in the climate?

Answer 40

• Sun spots
• Global dimming / Volcanic cooling

Question 41

What are sunspots?

Answer 41

Sunspots are the result of Magnetic storms which release increased solar radiation to Earth

Question 42

How often do sunspots occur?

Answer 42

An 11 year cycle has been identified

Question 43

How do sun spots create short-term changes in Earth’s climate?

Answer 43

As the number of sunspots increases, so does the temperature on Earth
- are evidence of high energy phases in solar activity

Question 44

What provides evidence for the effect sunspots had on Earth’s climate (UK example)?

Answer 44

1694 ‘frost fair’ on the Thames in London
- The Thames often froze in winter and ‘frost fairs’ were held on the ice
- During a period of colder temperatures known as the Little Ice Age, when winter temperatures were 2 degrees C lower than normal

Question 45

What was the coldest period of the Little Ice Age called?

Answer 45

The Maunder Minimum
- a period of few sunspots = low solar energy

Question 46

How long do Northern Hemisphere changes last?

Answer 46

10,000 years (average temperatures varied, but these are relatively small + short in terms of geological time)