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Climate Change, Less solar radiation reaches Earth's surface, creating…

- - - - Seafloor sediments and oxygen isotopes
        
        Earth formed 4.6B years ago
        
        past 650,000 years, temp. and CO2 lvls in atm increase and decrease in cyclical pattern
        
        through extracting and analysing oxygen isotope lvls
        
        Sediment cores record past climate
        
        varying oxygen isotope lvls in layers of sediment
        
        Higher concentrations of light oxygen (i.e. oxygen-16 isotope) in ocean
        
        warmer climate
        
        Higher concentration of heavier oxygen (i.e. oxygen-18 isotope) in ocean
        
        cooler climate
  - - - determined using most important parameter:
        
        temperature
        
        Example:
        
        18,000 yrs ago, Earth experienced Cooler temp (glacial period)
        
        large ice sheets formed over continents
        
        continental ice sheets melted
        
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        Currently
        
        rising sea surface & air temp.
        
        TC zone expanding in coverage
        
        increase in places experiencing drier-than-usual weather conditions
        
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  - - - changes in
        
        Earth's orbit
        
        stretches from circular to an elliptical shape and back again
        
        Most elliptic --> more solar radiation at its closest approach to the Sun than furthest departure from the sun
        
        cycle: 100,000 yrs
        
        Earth's angle of tilt
        
        varies back and forth between 21.5 and 24.5 degrees
        
        cycle: 41,000 yrs
        
        angle increase --> more extreme seasons
        
        Hemisphere receive more solar radiation during summer when tilted toward Sun
        
        Hemisphere receives less solar radiation during winter when tilted away from Sun
    - - Occurrence of sunspots
        
        Variations in solar output
        
        periods of max sunspot activity correspond to times of high annual temp of Earth
        
        rises and falls w a cycle of every 11 years
        
        Higher sunspot activity --> higher amt of solar radiation emitted from Sun
        
        area around surrounding sunspot radiate more energy
        
        Compensate for lower temp of sunspot areas
        
        short-term increase in avr temp.
      - Large-scale volcanic eruptions
        
        Release large vol. of CO2, water vapour, sulfur dioxide, dust and ash into atm
        
        sulfur-based particles, dust and ash spread around lower atm area
        
        Absorb and reflect solar energy back into space
        
        temporarily offsets greenhouse house effect
        
        Lower temp until particles grow large enough and fall down to Earth
        
        volcanic ash reflect more solar radiation back into atm
        
        Example: Mount Pinatubo in 1991
        
        drop in avr global temp. of 0.6 degree celsius over 15 months after eruption
- - - - increase in greenhouse gases in atm
        
        Example: CO2, CH4, N2O (nitrous oxide)
      - Examples: Coal, oil, natural gas
      - create energy for human activities
        
        agriculture
        
        operate farm machinery that harvest and transport crops
        
        industries
        
        Industrial Revolution in 1880
        
        burn fossil fuels for various activities became dominant source of energy
        
        run machinery/ factory processes that produce goods and services
        
        contribute 43% of GHG emission yearly
        
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        urbanisation
        
        power high concentration of vehicles/ household activites
        
        Cities consume 78% of world's energy and contribute significantly to emission of GHG
      - since 1970s, sudden steep increase in amt of CO2 emission to > 35B tonnes per year by 2020
    - - demand for resources and land increases
        
        use of land to support anthropogenic activities
        
        GHG increase
        
        each yr, tropical tree cover loss due to deforestation
        
        contribute to 20% of annual GHG emissions
        
        why increase?
        
        reduce no. of trees that absorb CO2 via phtosynthesis
        
        trees store carbon --> cut down or burned --> stored carbon release back into atm as CO2
        
        expose soil beneath to sunlight resulting in carbon oxidation
        
        make space for agriculture to meet rising demand for food
        
        contribute to 30% of annual GHG emissions yearly
        
        crop fertilisation using chemical fertilisers
        
        nitrogen in fertilisers convert to N2O (one of the most potent GHG) --> emitted into atm
        
        trap heat and contributing significantly to climate change
        
        lvls risen by 20% since 1960s, coinciding w Green Revolution
        
        Livestock rearing and natural decomposition processes
        
        emit methane
        
        around 40% of all athropogenic methane emission
        
        through burping/ release of waste gas
        
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        Paddy rice farming/ wet rice cultivation
        
        cultivation of rice in flooded fields
        
        contribute to total methane emissions from all anthropogenic sources
        
        CH4 produced when organic material decompose & escape into atm during growing season
    - - suggests CO2 concentration increase, global temp increase as well
- - - - Since 1850s, global mean temp. consistently higher than the previous decade
        
        match w increase in concentration of CO2 in atm
  - - - Most reach Earth's surface and is absorbed
        
        warms surface
        
        At night, Earth surface emit radiation it absorbed (longwave radiation)
        
        longwave radiation escape towards space
        
        Some absorbed by greenhouse gases in atm
        
        re-emitted back down to surface, keeping Earth warm at night
      - Some reflected and absorbed by clouds in atm
- - - - More heat trapped in atm
        
        result in unprecedented increase in global temp.
        
        threaten Earth's ecosystem/ ppl's way of life
        
        Ocean vv huge, temp change seem small --> over last century --> sea surface warmed by 1 degree celsius
        
        increase in ocean surface temp not uniform
        
        serious consequence on aquatic ecosystem
        
        all of world's ocean expected to experience increase in surface temp.
        
        Global Ocean circulations to slow down
        
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        Changes in precipitation on land
        
        global precipitation patterns altered by climate change (strengthening existing patterns)
        
        wet regions are expected to get wetter/ dry regions expected to get drier
        
        warmer air (hold more water vapour due to increase evaporation) --> increased water vapour in atm
        
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        warmer atm temp. --> increase evaporation --> reduce surface water --> dries out soil & vegetation
        
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      - less LWR and heat escape into space
        
        more heat radiated back towards Earth's surface