Climate and Change

Climate and Change

1. Past climate change

   • Natural causes of climate change
     • Earth's orbit changes slightly once every 100000 years (Milankovitch cycles)
     • Every 11 years, sun changes amount of energy emitted
     • Volcanic eruption pump ash into atmosphere, cooling it
     • Large asteroid collisions block sunlight, Fires from asteroids release CO2
     • Ocean current changes
   • How it's changed
     • When temp is cooler for a long time, more of the Earth covered in ice (Ice Ages/Glacials)
     • Now, we're in a warmer period (interglacial)

2. Impact of climate change

   • Little Ice Age, 15th-19th century
     • Winters were cold and summers were short. Crops didn't grow well so there was less productivity and food.
     • Could be caused by fewer sunspots or volcanic ash in atmosphere. But probably not humans because not a lot of industry.
     • Evidence from diaries, newspapers and paintings. Also, tree's rings are thinner in cold years.
   • Impact on megafauna
     • 1. Megafauna like mammoths and sabre-tooth tigers evolved during Ice Age.
     • 2. After Ice Age, temps rose 5C in 10000 years.
     • 3. Megafauna couldn't adapt and became extinct (hunting could also be a cause)

3. Present and future

   • Rise in greenhouse gases
     • CO2 and CH4 (Methane) are linked to human activity
     • Rise in greenhouse gases matches the start of industrial revolution
     • Current levels of CO2 thought to be at their highest for 650000 years
     • For CH4, highest in 900000 years
     • Methane is 21 times more potent than CO2
   • Reasons for rise
     • More greenhouse gases are released as a country becomes more developed
     • More CO2 because: More industry, more energy from fossil fuels needed, more transport, land is needed so there's deforestation (trees burned)
     • More CH4 because more animals are raised for meat
   • How greenhouse effect works
     • 1. Sun warms earth's surface
     • 2. Some warmth radiates into atmosphere
     • 3. Without gases warmth espaces into space
     • 4. But with gases, some warmth is trapped, we need them but not too much

4. Climate change challenges

   • UK climate
     • Latitude affects how much sun we get
     • North Atlantic current (drift) keeps UK warmer than other places on same latitude.
     • Air masses bring weather to UK from where they originated. UK affected by 5 air masses
     • Prevailing winds from Atlantic in south west pick up moisture and bring rain to the UK.
   • UK climate change
     • Possible changes include: Average temp rises, less predictable rainfall patterns, drier summers and changing seasons
     • Changes will happen because...
       • North Atlantic current likely to move, less rainfall
       • More air masses from north, more storms and extreme cold in winter
       • Paths of depressions (which bring rain) may be altered because of this.
   • Predicting effects
     • In 2008, global CO2 levels reached 380 ppm
     • If conc goes over 550 ppm, global temp may rise by 6C or more
       • Consequences: Millions of home losses due to sea level rises
       • Changes to weather patterns cause storms and droughts leading to famine and disasters
       • Animals and plants wouldn't be able to adapt
     • If conc stays under 550, global temp may not go over 2C
       • Sea levels may rise 1m, leading to costal flooding
       • More storms/ hurricanes
       • Some species might become extinct, others would shift to new zones

5. Case Study: UK

   • Environmental impacts
     • Sea levels rise, loss of coastal land and increased erosion. Low-lying cities like London may flood
     • Severe storms and longer droughts during summer
     • Fishing industry changes because species move to different waters
     • Some plant and animal species may move and invasive species could emerge
     • Warmer temp could encourage diseases like malaria
   • Economic impacts
     • Increase in refugees from countries hit hard by climate change
     • Warmer weather means farmers can grow different crops and have a longer growing season
     • Hotter summers, more people holiday in UK rather than overseas
     • Damage from flooding to cities like London would be expensive and disruptive
     • Cost of protecting places from flooding is expensive and sometimes not practical
     • Housing design may need to be altered so less water wastage

6. Case study: Bangladesh

   • Environmental impacts
     • River flooding could worsen because of rainfall and sea level rise
     • Tropical storms could be more frequent and move inland
     • Dry season already getting longer, more droughts
   • Economic impacts
     • More tropical storms would lead to increased damage to homes, lives and infrastructure
     • Bangladesh has large, growing population, many farm so land is needed
     • Cost of protecting from flooding is more than people or government can afford
     • Coastal flooding makes farmland too salty to grow crops
     • More flooding means more homes damaged and lives and economy disrupted
     • Even a few cm rise in sea level could reduce Bangladesh's agricultural output by a lot
     • Shrimp farming, which is important, could be affected by sea temp
     • Increased flooding spreads water-borne diseases like cholera

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