WCC: Carbon Cycle - Natural Causes of Change in the Carbon Cycle

Question 1

How would cold conditions impact chemical weathering?

Answer 1

It would be more active as cold water can hold more carbon dioxide

Question 2

How would cold conditions impact decomposition? How would this impact the carbon cycle?

Answer 2

It would decrease as decomposers would be less effective, so carbon transfer to soils would be reduced.

Question 3

How would cold conditions impact ocean stores? How would this impact the carbon cycle?

Answer 3

Ocean stores would be smaller as less water would have flowed into the oceans due to it being locked up as snow and ice on land. There would be less sediment transfer along rivers and less build-up of sediments on the ocean floor, reducing sedimentary rock stores.

Question 4

How would cold conditions impact soil? How would this impact the carbon cycle?

Answer 4

Soil would be frozen over vast areas of land, stopping transfers of carbon.

Question 5

How are wildfires started?

Answer 5

Lightning strikes

Human accidents or arson

Question 6

What are the 3 main natural variations that cause change in the carbon cycle over time?

Answer 6

Natural climate change - temperature
Wildfires
Volcanic activity

Question 7

How have global climates changed throughout the Quaternary geological period?

Answer 7

Climates have fluctuated considerably between warm interglacial periods and cold glacial periods

Question 8

Briefly describe the nature of the relationship between CO2 and temperature

Answer 8

Trends in temperature and CO2 over time mirror each other. Increased CO2 levels increase temperatures and lower CO2 levels decrease temperatures, but temperature change also has an impact on CO2 levels.

Question 9

Give evidence for the mirrored relationship between CO2 and temperature

Answer 9

Data obtained from ice cores in the Antarctic ice sheet shows that over the past 800,000 years, there have been several regularly occurring glacial periods interspersed with warmer interglacial periods. CO2 levels have risen and fallen along with these temperature changes.

Question 10

Name the carbon stores and transfers which would be directly impacted by temperature changes.

Answer 10

Weathering (chemical)
Vegetation 
Decomposition
Ocean store
Soil transfers
Permafrost

Question 11

How would colder conditions impact vegetation? How would this impact the carbon cycle?

Answer 11

Forest coverage would differ in total area and geographical location. This would affect the significance and distribution of photosynthesis and respiration.

Question 12

Where has the recent rise in temperature been particularly noticeable?

Answer 12

High latitudes for example tundra regions in Siberia, Russia

Question 13

What noticeable effect has the recent rise in temperatures had on tundra regions?

Answer 13

Melting permafrost resulting in a positive feedback loop

Question 14

Describe the positive feedback loop occurring in tundra regions due to recent rises in temperature.

Answer 14

Carbon stored within the permafrost is being released as it melts in the form of CO2 and methane. In the atmosphere, these gases further enhance the greenhouse effect, leading to increased warming and subsequent .melting.

Question 15

What is biomass combustion?

Answer 15

The burning of living and dead vegetation

Question 16

What are the 4 different cycles the carbon cycle can be divided into?

Answer 16

Fast organic carbon cycle
Fast inorganic carbon cycle
Slow organic carbon cycle
Slow inorganic carbon cycle

Question 17

Dsecribe the fast organic carbon cycle.

Answer 17

Operates from months to centuries and includes transfers of carbon via living things between atmosphere, soil and biosphere

Question 18

What is the fast inorganic carbon cycle?

Answer 18

Ocean-atmosphere exchange of carbon dioxide through diffusion

Question 19

What is the slow organic carbon cycle?

Answer 19

The long-term sequestration of carbon in the remains of plants and animals over hundreds of millions of years

Question 20

What does the slow organic carbon cycle create?

Answer 20

Fossil fuels - coal, oil, natural gas

Question 21

What is the slow inorganic carbon cycle?

Answer 21

The sequestration of carbon from the atmosphere in the hydrosphere and then sedimentary rocks which are brought back to the surface through tectonic activity and then weathered

Question 22

What 5 areas does biomass combustion occur most frequently in?

Answer 22

• Boreal forests in North America, Russia, Scandinavia
• Savannah grasslands in Africa
• Tropical forests in Africa, SE Asia, South America
• Temperate forests of US and Europe
• Agricultural areas of US and Europe

Question 23

In what ways do wildfires emit carbon?

Answer 23

Combustion of vegetation

Decomposition of vegetation (soil respiration)

Question 24

In what ways do wildfires result in the storing of carbon?

Answer 24

Production of new vegetation

Decomposition of vegetation (soil storage)

Question 25

What percentage of a forests carbon does a wildfire emit into the atmosphere?

Answer 25

10-20%

Question 26

Why do wildfires only emit a small percentage of a forest’s carbon into the atmosphere?

Answer 26

Wildfires kill trees but do not entirely consume them

Question 27

What determines whether a forest becomes a net source or a net sink after a wildfire?

Answer 27

The balance between production and decomposition

Question 28

What type of carbon cycle are the impacts of wildfires involved in?

Answer 28

Fast organic carbon cycle

Question 29

What 3 factors make wildfires more likely to turn forests into carbon sources?

Answer 29

Larger fires
More frequent fires
Presence of peat

Question 30

Which 5 carbon cycle stores and transfers are directly affected by wildfires?

Answer 30

Vegetation storage
Decomposition
Soil respiration
Combustion
Atmospheric storage

Question 31

Give 2 reasons for the increase in magnitude and frequency of wildfires.

Answer 31

Warming temperatures

Changing precipitation levels

Question 32

How much of the Earth’s land area do wildfires burn annually?

Answer 32

3-4 million km^2

Question 33

How much carbon do wildfires release into the atmosphere annually?

Answer 33

Over 1 billion tonnes

Question 34

Give an example of how wildfires can regional impacts.

Answer 34

In 1997-98 and 2013 many huge fires in Indonesia affected the lives of millions of people as smoke spread across SE Asia

Question 35

How much CO2 do volcanic eruptions emit annually?

Answer 35

130-380 million tonnes

Question 36

What do the USGS say about the contriubtion of volcanic activity to global warming?

Answer 36

The CO2 released in recent volcanic eruptions has never cause detectable global warming of the atmosphere?

Question 37

What are 2 reasons for recent volcanic eruptions not causing a detectable increase in the Earth’s temperatures?

Answer 37

CO2 emissions are counterbalanced by sulphur dioxide emissions
Not enough CO2 compared to human activities

Question 38

Why do sulphur dioxide emissions counterbalance the warming effect of CO2 emissions from volcanic eruptions?

Answer 38

Sulphur dioxide is converted into sulphuric acid, which forms fine droplets. This increases the reflection of radiation from the Sun back into space, cooling the Earth’s lower atmosphere.

Question 39

Give evidence to support that not enough CO2 has been emitted from volcanic activity compared to human activity to cause detectable global warming

Answer 39

Present-day sub-aerial and submarine volcanoes have released less than 1% of the CO2 released currently by human activities

Question 40

How does volcanic activity release carbon?

Answer 40

Carbon rich sediments are dragged into the mantle during subduction. Volcanic eruptions release the carbon into the atmosphere as volcanic gases e.g CO2

Question 41

How can volcanic activity result in the absorption of carbon from the atmosphere?

Answer 41

Volcanoes erupt lava, forming igneous silicate rocks that will slowly weather. This converts atmospheric CO2 to carbonate minerals in solution. These become ocean sediments and may become sedimentary rocks,

Question 42

Briefly describe what impacts volcanic activity has on the carbon cycle.

Answer 42

Large quantities of CO2 are immediately returned to the atmosphere. However CO2 can be very slowly absorbed from the atmosphere due to the formation of igneous rocks.

Question 43

By looking at temperature changes and atmospheric CO2 changes over time, which change appears to occur first?

Answer 43

Temperature change

Question 44

What do some scientists believe causes the cycle of glacial and interglacial periods?

Answer 44

Orbital change

Question 45

How does orbital change cause the cycle of glacial and interglacial periods?

Answer 45

Regular cycles of orbital eccentricity causes slight variations in the amount of sun’s radiation that warms up the Earth.

Question 46

How does the cycle of glacial and interglacial periods cause changing atmospheric CO2 levels?

Answer 46

Orbital change triggers temperatures to rise at the end of a glacial period. The warming of oceans and melting of frozen land surface releases a surge of CO2 into the atmosphere.

Question 47

Explain the relationship between temperature and atmospheric CO2 over time through cycles of glacial and interglacial periods.

Answer 47

Rising temperatures at the end of glacial periods causes a surge of CO2 into the atmosphere. This enhances the greenhouse effect, amplifying the warming trend and creating a positive feedback loop.

Question 48

How much of the most recent post-glacial warming is believed to have occurred after the rise in atmospheric CO2? What does this suggest about the relationship between atmospheric CO2 and climate?

Answer 48

90%, suggesting rises in atmospheric CO2 are a major cause of global warming, rather than increased temperatures being the reason for increased atmospheric CO2.