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Geography Lecture 6 (Annex: Evidence of a Changing Climate (Ocean (a)…

- - - - Refer to Lecture 2
    - - Arctic ice pack decreases at 209% per decade
        
        It has thinned from 3.1m to 1.8m in a decade
        
        Temps increased by 2.5 degrees, melting season increased by 2-3 weeks
        
        Glaciers are retreating almost everywhere (Alps, Himalayas, Andes, Rockies, Alaska, Africa)
        
        Spring snow cover in NH has decreased and is melting earlier
  - - - Refer to Lecture 2
    - - Refer to Lecture 2
  - - - Trees add a ring of material every year
        
        Thick ring = fertile, well-watered
        
        Thin ring = lower rainfall, not ideal
    - - Refer to Lecture 2
  - - - Refer to Lecture 2
    - - Temperatures have risen about 1 degree globally since the last 150 years
        
        Most of the warming occurred in the past 35 years
  - - - Refer to Lecture 2
    - - 10-25cm rise since the last century
        
        Relic coastlines and drowned coastlines indicate changing sea levels
        
        Rias (drowned valleys) in Cornwall
        
        Fjords (drowned glacial valleys) in Western Norway
        
        Raised beaches and drowned caves (Kings Cave on the Isle of Arran in Scotland)
    - - Oceans have absorbed much of the increase in global atmospheric temperature
        
        The top 700m of ocean has warmed 0.302 degrees Fahrenheit
  - - - Extreme weather events are increasing in frequency outside of the normal trends
        
        Number of high temperature events in the USA has been increasing while the number of low temperature events has been decreasing since 1950
        
        The USA has also witnessed increasing number of intense rainfall events
  - - - This record is limited to the age of the tree
- - - - Carbon Dioxide
        
        Chlorofluorocarbons (CFCs)
        
        Methane
        
        Nitrous Oxide
        
        Tropospheric Ozone
      - Carbon Dioxide is the most important
    - - Temperatures have increased by 0.9 degrees Celsius in the last 100 years
      - In the last 150 years, a rise in greenhouse gas concentration and introduction of CFCs have caused the EGHE. This rise in greenhouse gas emission is likely due to a larger human population, leading to more carbon producing activities such as agriculture and industrialisation.
  - - - A carbon sink is a natural reservoir that accumulates and stores carbon. It always takes in more than it gives out in the long run. It comprises of geological formations, forests, oceans among others. The process is called Carbon Sequestration
      - Plants
        
        Plants represent a global mass equivalent of about 1500 billion tonnes of carbon at any time
        
        Plants use carbon dioxide during photosynthesis and this has a net uptake of 60 billion tonnes of carbon dioxide per year
        
        As humans alter vegetation types and land-use, it reduces the carbon uptake of plants, and stores the carbon for a shorter amount of time
      - Ocean
        
        Carbon dioxide readily dissolves in water and the oceans provide a huge reservoir of carbon.
        
        About 88 million tonnes of carbon is released from the ocean every year, but about 90 million tonnes is taken in. Net uptake is about 2000 million tonnes annually
        
        Carbon is also found in bicarbonate and carbonate ions. As concentrates of carbon dioxide increase, carbonate and bicarbonate ions decrease, leading to a lower ability to absorb carbon
      - Soils
        
        Soils contain about 2000 billion tonnes of carbon
        
        About 300 billion tonnes are detritus (dead matter). Some of this carbon will be released as carbon dioxide and the rest will be converted into modified soil carbon
        
        As man converts soils to agricultural land, it reduces its carbon absorption ability and would cause rapid respiration and release large amounts of carbon
    - - When fossil fuels are mined, transported and burnt, we rapidly release large amounts of carbon into the atmosphere that would otherwise have been removed naturally through sedimentation of carbon
      - This caused a large increase in carbon dioxide concentrations (more than 400 ppm)
    - - 33% of carbon dioxide emissions over the last 250 years is due to changes in land use
      - Deforestation both reduces the amount of carbon dioxide housed by deforested regions and releases greenhouse gases directly, along with aerosols through biomass burning
      - This has produced a cumulative global loss of 200 thousand million tonnes of carbon sinks
      - By clearing forests to support agriculture, carbon in living things is transferred to the atmosphere
        
        Destruction of land to create farmland
        
        consequently leads to decline in photosynthesis
        
        When vegetation is burnt, it releases additional carbon dioxide
    - - The International Panel of Climate Change (IPCC) has greater and greater confidence that humans are the main cause of recent global warming
      - Natural changes are unable to explain the rate at which the climate is changing
      - Natural climate drivers are unable to explain the lower-level atmosphere expansion (carbon dioxide concentrations)
      - The concentration of lighter carbon molecules (those from fossil fuels) is higher near locations of fossil fuel combustion and deforested areas
  - - - Earth is warming, and it is largely due to humans and our activities (deforestation, burning fossil fuels, land-use) leading to excessive carbon release
      - The surface temperature has increased by 0.8 degrees Celsius since the last century
      - Climate change has led to many problems (sea level rise, hotter weather, more extreme weather events)
      - The impacts will last for a very long time and the severity of the impacts will depend on the follow-up actions of humans
    - - Projections of future climate change will depend on human actions within the next few years
      - Certain Earth system processes are not incorporated into current climate models as they are not fully understood
      - Climate change impacts are usually more prominent in regional and local scales, and are not as prominent in global models
      - Impacts of climate change also depend on the adaptability and vulnerability of human societies and natural systems
- - - - Solar Irradiance
        
        Earth's Geometry
        
        Milankovitch Cycles
        
        Volcanic activity
    - - Clouds
        
        Precipitation
        
        Deforestation/Reforestation
        
        Ice Albedo
    - - Thermohaline Circulation
        
        Ice loss
        
        Rapid release of greenhouse gases
- - - - Polar ice cores
        
        Advance and retreat of ice sheets
    - - Ocean floor sediment (foraminifera)
        
        Lake bed sediments (diatoms)
    - - Tree rings (dendro-chronology)
        
        Lake bed (pollen grains)
    - - Global temperature changes
        
        Greenhouse gases and Greenhouse effect
    - - Isotopic record
        
        Sea level changes
        
        Changing sea-surface temperatures
    - - Extreme weather events