Changing Climate

Changing Climate

1. Change in the distant past

   • Cycles between glacial and interglacial periods
   • 100,000 year cycles
   • CO2 levels spike in the interglacial periods

2. Changes in the recent past

   • Roman Warm Period
     • Warm enough to grow grapes
     • Temperature rose by 2 degrees celcius
     • Peaks in 200AD and falls back down to 400AD
   • Dark Ages
     • Crop failures lead to famines in Europe
     • -1 degrees in average temperatures in 700AD
     • Wet and cold weather
   • Medieval Warm Period
     • 1.7 degrees average increase at 1200AD
     • Improving yield crop as temperatures rise.
   • The little Ice Age
     • Thames regularly froze over during 1500 and 1850
     • -1 degrees in average temperature in 1600
     • Further decline to -2 degrees average temperature in 1800

3. Natural Causes of climate change

   • Eruption Theory
     • Only possible with large and explosive volcanoes
     • Two important bi-products: Ash and sulphur dioxide
     • Stops sunlight reaching the Earth's surface
     • Cools the Earth's surface and lowers the average temperature
   • Sunspot Theory
     • Dark spots show that the sun is more active than usual
     • Colder periods may have been caused by sunspot activity
     • During the little ice age there were less sunspots and over 200 were recorded in the medieval warm period
     • Sunspot activity changes climate for 100-300 years
   • Asteroid Theory
     • Asteroids throw dust into the air
     • Blocks sunlight and changes global temperatures
     • Large impacts to food chains
     • Asteroid impact ended the dinosaurs 65 million years ago
   • Orbital Theory
     • Earth's orbit transitions from a circular one to an elipse
     • Earth's axis can tilt from 22.5 degrees to 24.5 degrees
     • Takes 100,000 years for the orbit to change
     • 41,000 years for the axis to tilt and straighten

4. Impacts of past climate change in the Little Ice Age

   • Social
     • 1693 failed harvests caused million of people to die
     • Sheep and cattle struggled to adapt
     • In wet and cold summers diseases spread like St Anthony's Fire
   • Environmental
     • Trees in England and Scotland changed from oak to pine trees
     • Peat bogs became bigger and wetter so agriculture had to be abandoned
     • Soils in the north became more acidic
   • Economic
     • Price of crops and grain increased from failed harvests
     • Growing season shortened by 2 months
     • Less taxes collected from food produced

5. Impacts of past climate change with mega fauna

   • Suitable environments had plants that were difficult to eat
   • Disruption to the food chains, meagafauna weakened from climate stress
   • Hunted by humans that migrated there
   • Herbivores going extinct meant carnivores had nothing to prey on