1.11. Changes To The Carbon Cycle Flashcards
Fossil fuel extraction and combustion evidence
- Burning of coal, oil and gas releases 90% of Co2 into the atmosphere
- Annual emissions are 61% higher than 1990 - China (28%), USA (14%) and India (7%)
How does fossil fuel extraction and combustion affect the carbon cycle?
The biosphere and hydrosphere are only able to absorb half of this excess, resulting in the atmospheric carbon store swelling by 80ppm since 1960.
Cement manufacturing evidence
- Cement production releases 5% of all Co2 emissions into the atmosphere
- For each 1000kg of cement produced, 900kg of Co2 is released into the atmosphere
How does cement manufacturing affect the carbon cycle?
Calcium carbonate is heated to separate lime and carbon dioxide -> heat often comes from burning fossil fuels
Farming processes evidence
- 44% of agricultural Co2 comes from Asia, 25% from Americas
How do farming processes affect the carbon cycle?
- Animals release Co2 and methane when respiring and digesting food
- Ploughing can release Co2 -> microbial activities increase in soil layers inverted by ploughing, resulting in increased respiration
- Growing rice in paddies releases methane
- Increased population increases food production
Deforestation evidence
- 13 million hectares of forests cleared for agriculture, logging or way to make developments
- 3% of forests lost between 1990 and 2005 at 200km squared per day
How does deforestation affect the carbon cycle?
Clearance reduces the size of the carbon store and if cleared forest is burned, there’s a rapid flow of carbon from biosphere to atmosphere
Land use change evidence
- Urban areas grow by 1.3 million people every week -> more than 50% of the population
- 2012: cities responsible for 47% of global carbon emissions
How does land use change affect the carbon cycle?
- Come from switch from natural vegetation to urban surfaces
- Increased energy consumption for transport, industry and domestic use
- Cement manufacture for urban dwellings
Carbon sequestration evidence
- Power station built in Canada -> burns coal, captures the emissions and powers 100,000 houses in the area
How does carbon sequestration affect the carbon cycle?
- Injecting captured Co2 as a liquid deep underground into a variety of stores
- Terrestrial sequestration-> use of plants to capture Co2 from the atmosphere, carbon stored as biomass in stems, roots and nearby soils -> stored carbon can be lost through forest fire -> slow growing and not permanent
Natural wildfires evidence
- Negative feedback loop
How do natural wildfires affect the carbon cycle?
- Rapidly transfer large quantities of carbon from biomass to atmosphere
- Loss of vegetation decreases photosynthesis so less carbon removed from the atmosphere
- Long term -> fires can encourage growth of new plants, take in carbon from atmosphere for photosynthesis
- Fires can have a neutral effect on amount of atmospheric carbon
Volcanic activity evidence
- Recent eruptions have released much less Co2 than human activities (1% of total)
How does volcanic activity affect the carbon cycle?
- Releases carbon stored within the earth in magma in the atmosphere
- There is potential for a very large eruption to disrupt the carbon cycle significantly
- Intense Co2 release in the geological past caused enough increase in atmospheric Co2 levels to cause a rise in temperature and possible mass extinctions
Natural climate change evidence
- Over the last 2.6 million years, global climates have fluctuated between warm and cold periods
- Milankovitch cycles - every 100,000 years, Earth’s orbit become more elliptical, triggering ice ages
How does natural climate change affect the carbon cycle?
During cold periods:
- Carbon stored as biomass would have become incorporated into permafrost = less atmospheric Co2
- Increased chemical weathering (cold water holds more Co2). As a result, more Co2 is transferred from the atmosphere
- Oceans are more saline during cold periods. They take up greater amounts of carbon from the atmosphere via the oceanic pump.
