ENV1800 7: Carbon cycle & Climate Change

Define carbon stores

Places where carbon remains for long periods of time before moving to the next step in the carbon cycle

• Not all Co2 is taken up by plants is immediately respired and released back into the atmosphere

What are the 3 carbon stores/reservoir? (Big Hunky Latino)

1. Biosphere - Includes all living organisms (plants, animals, microorganisms, fungi)

• Carbon stored in organic molecules (carbohydrates, proteins and fats)

Hydrosphere - ocean, river and lakes

• ocean is carbon sink stores carbon in dissolved form and marine organisms

Lithosphere - earths crust and soil

• Rocks, sediments and fossil fuel or organic soil for hundred and millions of years

Elaborate on the biosphere

Includes all living organisms (plants, animals, microorganisms, fungi)

• Includes carbon in living tissues as well as organic material in the soil (dead too)

• Carbon is stored in organic molecules (carbohydrates, proteins, and fats)

How can the carbon stored in the biosphere be categorized?

Above-ground carbon storage

• Carbon contained in molecules forming tree trunks and branches, leaves, and wood on the forest floor

• Respiration and decomposition emit some CO2, but the majority of forest carbon remains part of living plant tissue

Below ground carbon storage

• Carbon is contained in molecules in living tree roots and soil (partially decomposed materials)

How does the below-ground carbon vary in peatlands and mangroves?

Decomposition occurs very slowly due to waterlogged soil

• Large amounts of carbon accumulate and can be stored for centuries

Waterlogged soil fills the pores in the soil, preventing oxygen from entering —> anoxic soil

• microbes for decomposition are less efficient in anaerobic conditions —> slower rate of decomposition

Explain the hydrosphere

Co2 from the atmosphere dissolves into ocean surface waters (important carbon stores)

• holds 50x more carbon than the atmosphere

• some dissolved CO2 from the atmosphere is taken up by seaweed, seagrass, and marine phytoplankton (tiny photosynthetic organisms)

What do phytoplankton do?

Fix carbon into organic molecules —> take loose inorganic co2 from air or water to turn it into solid, energy-rich organic compounds

using SUNLIGHT

• e.g sugar / proteins

Form base of marine food web which can be consumed by the next trophic levels

What happens when marine animals or phytoplankton die? 2 paths

1. Some sink to the seabed —> decompose and release CO2

2. Some buried by layers of sediment —> over millions of years, organic carbon inside the molecules form sedimentary rocks and, under specific conditions (low oxygen areas), may form fossil fuels

What is the difference between the process of obtaining natural gas and petroleum as compared to coal?

Natural Gas & Petroleum

• Marine organisms such as phytoplankton

• Big oil companies usually located in the middle of the ocean

Coal

• Plants in peat swamps

• low oxygen areas causing less decomposition

Why do marine organisms sink down to the seabed?

Gravity and biofouling

Biofouling - undesirable accumulation of microorganisms such as algae and plants or small animals on surfaces

Two pathways for the hydrosphere carbon store

Gas diffusion in the ocean

• exchange of CO2 between the atmosphere and the surface of water

• bidirectional controlled by concentration gradients and temperature

Weathering

• CO2 gas mixes with H2O from rain to form carbonic acid

• Acidic rain falls on rocks and dissolves ions (calcium, silicon) —> river —> sea

• Ca + Co3 used by marine animals to make shells/skeletons/external plates (molluscs, corals, coccolithophores)

What happens to CaCO3 when marine animals die?

Shells (CaCO3) fall to the ocean floor and become compressed to form limestone rocks

Hydrospheres act as both short term _____ and long term _____? Explain.

Short-term carbon sinks

• gas exchange and dissolution

• bidirectional
  
  

Long-term carbon storage

• when marine organisms die and sink and majority of the carbon is kept at the seafloor and eventually turn into sedimentary rock

• last thousand to million of years

Lithosphere carbon store

Stored in rocks; fossil fuels (coal, oil and gas)

Process of Natural gas and Petroleum formation

1. Tiny marine plants and animals died and were buried on the ocean floor

• Overtime, animals were covered by layers of stilt and sand (no oxygen)

2. Over millions of year, remains were buried deeper and deeper. Enormous heat and pressure from earths interior turned kerogen into hydrocarbon (compound made to form natural gas and oil)

• lighter hydrocarbon - natural gas

• heavier hydrocarbon - crude oil

• substance migrated through porous rocks until trapped between impermeable rock formations known as cap rocks

3. Now we drill down through layers of sand, stilt and rock to reach rock formations that contain oil and natural gas deposits

Process of coal formation

1. Many giant plants died in fell into swamps (low oxygen prevent from fully decaying)

2. Over millions of years accumulation dead plants (peat) buried under water and dirt

3. Heat and pressure from the earths interior turned the dead plants into coal

What are coal deposits?

Sedimentary rocks: types of rocks that form by the accumulation of small particles of pre-existing rocks or organic materials and the compression of these particles on the floor of oceans and peat swamps at the earth’s surface.

What is the process used to turn peat into different grades of coal called and what are the requirements

Coalification.

• time

• pressure

• heat (earths interior)

Coalification process with increasing pressure and heat

1. Peat

2. Lignite (brown coal) - soft and low carbon content

3. Sub-bituminous and bituminous coal - thicker and denser

4. Anthracite - hardest and highest carbon content

Why is the carbon cycle about balance?

• process that remove co2 from the atmospshere - photosynthesis

• process that add co2 to the atmosphere - combustion of fossil fuel

What are greenhouse gases?

Atmospheric gases that trap heat, raising the surface temperature of the earth. Absorb the infrared radiation the earth emits after being heated by the sun, resulting in the greenhouse effect.

What are the 5 major GHG in the

1. Water vapour - the most abundant major greenhouse gas, warm gas holds more water vapour

2. CO2 -

3. Methane, CH4 - powerful but short lived

4. Surface-level ozone, O3 harmful air pollutant

5. Nitrous oxide (N2O) - agricultural fertilizer and fluorinated gases - human made used in fridges

How is surface-level ozone different from the ozone layer in the atmosphere?

Ozone layer: a beneficial shield in the upper atmosphere stratosphere

Surface-level ozone is a harmful air pollutant in the troposphere.

The effect of each gas on Earth’s temperature depends on 3 factors:

1. Concentration/number of gas molecules in the atmosphere

2. Strength - how effective each molecule traps heat

3. Lifetime - how long it can last in the atmosphere before broken down

Determine whether the molecule have a large or small effect on the climate.

Greenhouse effect

Natural process that warms the earth’s surface

• some energy from the sunlight is absorbed and re-radiated as infrared energy by GHG

What does the earths surface temperature depend on?

How much heat energy (infrared radiation) is trapped near the surface by GHGs in the atmosphere

What are the increases in carbon dioxide seen throughout the years?

2023 may: 424 ppm

2024 may: 426.90 ppm

2025 may: 430.51 ppm

Co2 concentration now and back in 1750s is?

2025 - 430.51 ppm

1750 - 280 ppm

• Last time Co2 concentrations were 350 ppm was approx. 1 million years ago

• Change in atmospheric CO2 is 100x faster than natural fluctuations in CO2

When did the industrial boom happen? What year

1950s

The increase of GHG throughout the years anthropogenic

CO2 - increase by 80-90%

Methane - increase by 20-30%

Nitrous oxide - 30-40%

Flourinated gas - 400-500%

CO2 remains____

CO2 remains the largest anthropogenic source of GHG emissions

Why do short-lived fluorinated gases have high global warming potential?

Intense radiative efficiency

• trap infrared radiation much more effectively per molecule than carbon dioxide

The largest sector for the greenhouse gas emissions

1. Electricity and Heat

2. Transport

3. Manufacturing and construction

Impacts of human alteration to the carbon cycle

1. Combustion of fossil fuels for electricity, transport and industry

2. Land use change (clearance of tropical forests for agriculture, livestock farming)

Combustion of fossil fuels

• release carbon dioxide from underground carbon stores

• increase carbon dioxide concentration

Land use change 2 effects

Conversion of land to agricultural land

• Reduces biomass of trees (carbon sequestration is reduced)

• Soil disturbance - peat soils drained or burned to make way for plantations
  -soil rich in stored carbon releases co2 and ch4 into the air

In undisturbed water-logged peatland, what happens and when drained what happens?

Anaerobic soil conditions prevent full decomposition; carbon remains stored in peat for thousands of years

• some methane is produced by microbes

When drained,

• oxygen enters the soil

• causes decomposition —> massive amounts of carbon released

4 key impacts of climate change

1. Increasing global temperature
   - loss of snow and ice cover
   - mass coral bleaching
   - sea levels rise
   
   

2. Changes in precipitation
   - flood risk
   - drought
   
   

3. Food production

4. Ocean acidification

Increasing global temperatures

• According to NASA earth temperature has increased by approx. 1 degree celsius since 1880s

• 2/3s of the global warming has occurred since 1975, at a rate of 0.15 to 0.25 per decade (10 yrs)

• Asia predicted to rise 3 degree celsius by 2050, and 5 degrees by 2080 based on current CO2 emissions

• Increased temperature, working outside over 35 degree celsius hazardous to human health

• India has already lost 3% of available daylight working hours annually due to high temperatures

Temperature change has been variable

Faster warming towards the Arctic Ocean (Arctic amplification)

Increasing global temperatures: Loss of snow and ice cover

• White ice and snow —> high albedo (ability to reflect solar radiation)—> less heat absorbed at Earth's surface
  
  

• exposed to the ocean and land, darker in colour, which absorbs significantly more heat

Case study loss of ice and snow

Melting of glaciers —> changes in water supply for large asian rivers

E.g Himalaya - Hindu Kush Mountains and Tibetans plateau, home to 100,000km² glaciers the melt during the N hemisphere summer

• supply water to many rivers e.g yangtze river

• increase river flow and flooding

Long term - water availability to decrease

• threaten food production and irrigation

Increasing global temperature: Mass coral bleaching case study

Coral bleaching in Australia’s Great Barrier Reef

• 22% were killed as a result of severe coral bleaching

• Economic importance (tourism and job availability)
  - 5.7 billion for the economy
  - 69000 jobs

• at least 275 million people depend on corals for their livelihood (fish)

Increasing global temperature: Sea levels rise - 3 main causes

1. Thermal expansion of seawater

2. Melting of mountain glaciers

3. Melting of Greenland and antarctic ice sheets, which flow into the sea

Sea levels rise data

Current rate of increase: approximately 3mm/year

• 30cm rise by 2050

• Up to 1m rise by 2100 if GHG continue to rise

Consequences of rising sea levels

Storm surge (high tide + storm conditions) —> amplifies the effect of sea-level rise

• Coastal flooding

• Soil erosion

• Salt water intrusion

Dangerous for coastal cities e.g., Vietnam, Jakarta, Bangkok

• home to millions

Why is Jakarata a critical hotspot for the impact of rising sea levels?

Faces compounding threats due:

• rising sea level and land subsidence from excessive ground water extraction

• fastest sinking countries in the world

Increasing global temperatures: Changes in Precipitation

Precipitation intensity: the proportion of rain that falls within a certain amount of time

• Precipitation intensity is predicted to increase in 2100 (higher rainfall in shorter amounts of time)

• rainfall more erratic and unpredictable

• Blue represents increase precipitation and brown represents decrease precipitation

Return period

Projected years between major floods (frequency of major floods) in the 21st century

• shorter return period - floods more frequent

• longer return period - floods more rare

How does changes in precipitation lead to drought?

Global temperatures rise —> increased evaporation of water —> increased risk of droughts

• not all droughts are caused by climate change; they may have other factors e.g water management

Food production

Changes in temperature and rainfall patterns will affect food production

Major crops (wheat, maize and rice) predicted to:

• Warmer temperature - increase yield at moderate temperatures increases in mid to high-latitudes

• High temperatures and irregular rainfall - decrease yield at low latitudes close to the equator

Rice yield predicted to decrease by 10% for every 1 degree celsius increase above 30 degree celsius

• increase co2 reduce nutritional quality of grains (zinc and iron)

Ocean acidification

Absorbs 30% of CO2 in the atmosphere from human activities

• co2 dissolves in water to form carbonic acids

• decrease in ocean pH due to increase in H+ ions

• More H+ ions less co32- ions

• marine animals require more energy to grow in low pH seawater

• increase death of corals, oysters and scallops

Expected atmospheric CO2 concentrations in 2050

467 - 555 ppm —> pH 7.8 from 8.1

Not small change as pH range is logarithmic

• a 0.1 drop represents a 30% increase in acidity

• lower carbonate ions present for animals to build shells, reduce amount of phytoplakton and marine life

Healthy vs non-healthy snail shell

Healthy shell - smooth contoured ridges

Unhealthy shell - cloudy, ragged with kinks

Responding to climate change

1. Adaptation - adjusting our societies and economies to cope with the changes that are already happening
   
   

2. Mitigation - addressing the root cause of the problem
   - reducing GHG emissions
   - enhancing carbon sinks

Define climate mitigation and adaptation

Climate mitigation: a human intervention to reduce the sources or enhance the sinks of GHG

• actions to limit the magnitude or rate of long time climate change

• reducing GHG emissions or increasing absorbtion of GHG from the atmosphere
  
  

Climate adaptation: The process of adjustment to actual or expected climate and its effects.

• aims to moderate harm or exploit beneficial opportunities

• reduce the vulnerability of people to the consequences

Strategies that involve mitigation and adaptation

• water conservation

• new energy systems

• local food

• education

Climate adaptation

action to manage the risks of climate change impacts

What are nature based solutions

Work with nature by protecting, restoring or sustainably to benefit biodiversity and local community

E.g countries integrate farming with rubber and fruit trees

• reduce soil erosion - extensive root systems to physcially bind soil particles

• improve resilience to drought