Carbon cycle

Question 1

Carbon cycle

Answer 1

Flows of C between stores in a biogeochemical cycle that drives and is driven by others

Question 2

How much C does Earth have

Answer 2

65,000b metric tonnes C, 4th most abundant element. Hydrosphere, lithosphere, atmosphere, biosphere most to least

Question 3

Physical causes of C flows

Answer 3

Natural climate change, wildfires, volcanic activity

Question 4

Human causes of C flows

Answer 4

Fossil fuel combustion, de/afforestation, urbanisation, agriculture, land use change

Question 5

Carbon budget

Answer 5

Balance of exchange between 4 C stores. Estimated amount CO2 (1000 Pg C) we can emit and limit global temperature rise to 2C from 1750, UNFCCC target. Used over 50%, use by 2045 if rates continue

Question 6

Radiative forcing

Answer 6

Difference between insolation absorbed by Earth and energy radiated back to space, increased 84% in past decade. CO2 65% contribution

Question 7

Weathering

Answer 7

Part of slow C cycle. Chemical e.g. carbonation with CaCO3. Biological e.g. burrows. Physical e.g. freeze thaw

Question 8

Volcanic activity

Answer 8

Part of slow C cycle. 130-380m tonnes CO2 released annually from eruption and subduction

Question 9

Oceanic C sequestration

Answer 9

Part of slow C cycle. C dissolved in ocean used in shells and skeletons that sink to floor, forming rocks like limestone and coal (plants), oil and gas from heat and pressure over time

Question 10

Diffusion

Answer 10

Part of slow C cycle. CO2 diffuses in and out of ocean driven by physical (current) and biological (photosynthesis) C pumps

Question 11

Fossil fuel burning

Answer 11

Part of fast C cycle. Only significant decrease

Question 12

Photosynthesis, respiration and decomposition

Answer 12

Part of fast C cycle. Affect atmosphere and biosphere stores

Question 13

Wildfires

Answer 13

Part of fast C cycle. Burn 3-4m km2 land annually, increase with radiative forcing, some species and old trees more susceptible so less biodiversity and C storage, controlled with fire breaks and suppression

Question 14

1959-2010 N hemisphere atmospheric CO2 conc variation

Answer 14

3ppm total, Feb dip exception from pattern, -2ppm in August, +1ppm in August

Question 15

Annual worldwide C changes due to plants

Answer 15

Equatorial constant, deciduous trees in Winter affect, opposite Summer

Question 16

How old are the first fossil fuels

Answer 16

650m year old organisms

Question 17

How much CO2 released annually from burning

Answer 17

21 Pg, 60% naturally absorbed

Question 18

How many Pg CO2 added to atmosphere annually

Answer 18

8

Question 19

Emission increases since 1750

Answer 19

40% CO2, 150% CH4, 20% N2O

Question 20

Carbon sequestration

Answer 20

Natural or human capture and long term storage of atmospheric CO2 to mitigate global warming

Question 21

Natural carbon sequestration

Answer 21

Iron fertilisation, urea fertilisation, mixing ocean layers, peatland restoration, agriculture, wetland restoration, reforestation

Question 22

Human carbon sequestration

Answer 22

Subterranean injections, deep basalt storage, (BE)CCS, acid neutralisation, biochar

Question 23

Positive effects of not tilling soil

Answer 23

40% C that plants absorb into soil, less desertification that displaces 40m annually, 1930s dust bowl, less water retained