booklet 3 +4 - factors leading to change

• human factors causing change in carbon cycle: Land use change - deforestation, farming, urbanisation

  hydrocarbon fuel extraction
• changes in the carbon cycle - deforestation: - estimates 13 million hectares (same size as greece) are cut down every year

  - over 361 mha cut down between 2001 and 2018 - this has released approx 98.7 Gtc of CO2 into atmosphere

  - however, planting of trees has meant forests are being established / extended
• changes in carbon cycle - farming practices: - when soils ploughed, it results in soil matter breaking down, releasing carbon

  - agriculture + forestry cause 1/4 of human emissions

  - 1/3 of soils are degraded, releasing 78 Gtc

  - livestock accounts for 14.5% of all human carbon emissions
• changes in the carbon cycle - urbanisation: - as cities grow, land use changes to built up land

  - CO2 emissions are increasing from urbanisation

  - estimates that 75% of global emissions are due to urban areas
• changes in the carbon system - hydrocarbon fuel extraction: - fossil fuels extracted and burnt producing CO2 and water

  cement industry produces around 5% of global anthropogenic CO2 emissions.

  
  

  need a lot of heat and energy to break down the limestone for cement

  - rising pops mean more urbanisation = more reliance on cement

  100kg of cement = 900kg of co2
• changes in the carbon cycle - burning fossil fuels: in 18th cent burn coal for industry - industrialisation

  Burn coal for transport

  An increasing population = more reliance on energy

  
  

  half the population in rich countries responsible for 86% of all fossil fuel emissions
• natural factors causing change in carbon cycle: natural climate change - impacts of warm/cold conditions

  wildfires - lightning + human causes

  volcanic activity
• changes in the carbon cycle - volcanic activity: - warming effect of CO2 emitted is counterbalanced by sulphur dioxide released

  - this converts to sulphuric acid which increases radiation reflection + lowers earths temp

  - CO2 released hasnt been enough to produce detectable global warming

  - produced less than 1% of CO2 released
• changes in the carbon cycle - wildfires: - can start by lightning strikes or human activity

  - have regional impacts

  - can turn forests from carbon sinks to carbon source as combustion releases large amounts into atmosphere
• changes in the carbon cycle - impacts on warm conditions: - global temps have risen, creating melting of permafrost in tundra regions

  - CO2 + methane in permafrost are released, enhancing greenhouse effect, leasing to more melting (+ve feedback)
• changes in the carbon cycle - impacts on cold conditions: - chemical weathering processes = more active due to cold water holding more carbon

  - soil would be frozen, stopping transfer of carbon

  - forest coverage would change, affecting photosynthesis + respiration levels
• Industry waste: industrial processes produce methane which is 30x more powerful than c02

  as waste breaks down from, industrial process (wood, oil, paper, food) methane is released
• How are the cryosphere changes in the Siberian tundra creating a positive feedback loop? as summer and winter temps rise --> snow and ice cover reduces --> lower ice albedo --> increased solar radiation absorbed --> air gets warmed --> temps rise
• What has caused a vast amount of carbon to be locked up in the permafrost? - organic matter has accumulated in the Siberian tundra

  - ice sheets ground up and pulverised exposed rock in fine particles that were blown by winds to form thick deposits

  - vegetation grew rapidly in each new accumulation deposited on top of the permafrost that contained plants from the previous glacial period

  - in next advance the most recent layer of top soil was frozen and became part of the permafrost
• different conditions that result in the release of co2 and methane: High global temps caused rapid melting go the permafrost which releases organic matter back into active layers with microorganism present

  
  

  Decomposition that takes place when Co2 is present leads to bacterial digestion of the thawed vegetation which relates co2

  methane is released in the anaerobic conditions of the swampy surface layer of thawed tundra
• Why is the Yedona region of Siberia important and how does it compare to global permafrost? Yedona region is important as deposits are high - 50-90% carbon

  covers 1 million square km

  contains between 210-450 gt of carbon

  
  

  entire global permafrost is approx 1400 gt - twice as much as atmospheric content at 850 gt
• the tundra is acting as a carbon sink. Why is this? the growth of tundra is stimulated as growing seasons are much linger meaning more carbon is absorbed by active vegetation than melting permafrost releases
• What are the future concerns and what might happen when the 'tipping' point is reached? if atmospheric temps rise and more permafrost melts than exchange will become revered with greater output of carbon into atmosphere from co2 and ch4 than plant growth absorbs

  
  

  Tipping point - continued temp rise will lead to a negative cycle where enhanced vegetation is fertilised and will increase the amount of atmospheric c02

  This will be replaced with a destructive positive feedback loop accelerating further warming as more co2 is released
• Patterns of temperature and c02 over last 800,000 years: as temps go up = higher co2

  Strong correlation between the two
• Are the current CO2 levels reflective of past patterns? current rates are not reflective of past patterns - there is bigger range closer to present and co2 concentration has shot up
• carbon sores changing the most: Atmosphere - changing exponentially

  due to human behaviour - fossils fuel combustion and hydrocarbon extraction

  
  

  Biosphere - store ins increasing due to vegetation - extra co2 is stimulating vegetation growth
• carbon stores changing the least: cryosphere - change slowly but will change quicker in the future

  could become a carbon source

  
  

  hydrosphere - ocean is the most stable store

  thermohaline cycle circulating carbon round
• Why is it that it is difficult to predict what impact changes in carbon stores is having on the planet: because its very unpredictable
• ocean acidity - change: since 1750 the ph of ocean surface has dropped by 0.1 - a 30% change in acidity
• impact of ocean acidity on coral reefs and phytoplankton: coral reefs -

  home to 1/4 of ocean animals

  marine heatwaves are causing widespread coral bleaching which occurs when coral is under stress

  weak coral threaten whole food chain

  
  

  
  

  sea creature -

  sea creatures likes clams, their shells are getting weaker due to carbonate ions reacting with co2 to produce hydrogen ions which compete with shells for carbonate

  this process means it harder for phytoplankton to grow and fine carbonate for food

  
  

  hydrogen ions make the ocean more acidic
• ocean warming: negatives

  - kills off symbiotic algea which coral reefs need to grow

  - decrease the abundance of phytoplankton - ideal is cool temps

  --- limits the ocean ability to take carbon from atmosphere and lessen effectiveness of ocean as carbon sinks

  
  

  positives

  - co2 is essential fir plant growth = more growth and so take more co2 from water
• sea ice: in last 35 years satellites monitoring sea ice have measured retreat of 40%

  
  

  when sea ice melts it is an indicator of warming climate

  it is also part of a feed back mechanism where ice is replaced with more heat absorbent water

  when this melts the ocean starts to absorb more sun

  
  

  loss of algea found in more concentrated form in the sea ice - large impact on ocean food chain
• ocean salinity: water in far north is cold and ver saline - make sit denser and heavier

  there has been an observed decrease in salinity in the North Atlantic - diem to higher river runs off and melting Greenland ice sheet

  
  

  changes have been linked to a possible slowing down of large scale oceanic circulation in north east Atlantic
• sea level rise - causes and impact on coastal areas: melting of terrestrial ice

  thermal expansion

  
  

  if earth continues stop warm up oceans can rise by 20-60 cm by 2100

  
  

  coastal areas - increase in flooding, submergence of land, higher tides, increased coastal erosion
• What is the natural greenhouse effect? the process by which the Earth's atmosphere warms the Earth and keeps the planet habitable
• Explain how greenhouse gases warm Earth.: Solar Radiation Reaches Earth

  The Sun emits energy, mostly as visible light and shortwave radiation. This energy passes through Earth's atmosphere and reaches the surface.

  
  

  Earth Absorbs and Reradiates Energy

  Earth's surface absorbs the sunlight and warms up. It then radiates heat back into the atmosphere as infrared radiation (longwave radiation).

  
  

  Greenhouse Gases Trap Heat

  Greenhouse gases (such as carbon dioxide (CO₂), methane (CH₄),
• What is the enhanced greenhouse effect? The enhanced greenhouse effect, is the impact on the climate from the additional heat retained due to the increased amounts of carbon dioxide and other greenhouse gases that humans have released into the earths atmosphere since the industrial revolution.
• What is radiative forcing and how has it changed? if the balance between incoming and outgoing energy is nothing other than zero, there has ti be warming going on

  
  

  the amount that the earths energy budget is out of lawn is called the radiative forcing