Changing Climate

Changing Climate

1. Past Climate Change

   • Know has changed in past by...
     • Fossils of animals and plants that no longer exist
     • Evidence of Glaciation in now ice free regions
     • Evidence of rocks showing climate conditions when the rocks were formed
     • Evidence from ice cores in Greenland and Antarctica showing how much CO2 was in the atmosphere
   • In the past 400,000 years there has been a Quarternary period.
     • Temperatures varied 1.5 degrees either side of the average
       • This small change makes a huge difference in what can be grown

2. Causes of Climate Change

   • Volcanic Eruptions
     • Large eruptions emit vast quantities of dust
       • Emitting gases such as sulphur dioxide into the atmosphere
         • This blocks out or absorbs solar radiation, so the Earth cools.
   • Sunspot activity
     • Sunspots are darker areas on the sun's surface
       • They are a sign if greater solar activity
         • They come and go in 11 year cycles
           • However, they have been observed in longer periods such as 1645-1715
             • A period which coincides with the Little Ice Age
   • Changes in Earth's orbit and rotation
     • The shape of the earth's orbit changes
       • It becomes more or less circular
         • This happens over 100,000 year periods, known as Orbital Eccentricity
           • The Earth wobbles on its axis over 26,000 years, known as precession.
             • The tilt of the axis varies between 21-24 degrees over 40,000 years
               • When used together these effects change the amount of solar energy the Earth's surface receives

3. Little Ice Age

   • Approx 1300-1870,
     • Approx 1 degree lower average temperature than today.
   • Impacts
     • The Baltic Sea froze over in winter
       • Many other rivers in Europe did the same.
     • Sea Ice from the North reached as far south as Iceland
     • Winters were much colder and longer
       • This reduced the growing season dramatically
       • Led to widespread crop failure and famine
         • The price of grain increased everywhere
           • Leading to social unrest and revolt
     • Remote areas abandoned
       • Such as Greenland, as survival became impossible
     • Glaciers advanced in the Alps and Northern Europe
       • Overran towns and farms

4. Megafauna and the Ice Age

   • 10,000-15,000 years ago the Ice Age ended
     • Temperatures rose as much as 5 degrees
       • Many megafauna disappeared completely.
         • It was a mass extinction event
           • EG: Mammoths, Sabre-tooth tigers and giant beavers became extinct.
             • WHY?
               • Their preferred food disappeared so they died out.
               • Humans hunted them
                 • We know this from evidence from remains

5. UK Climate today

   • UK has a maritime climate
     • Is mild and wet
     • Precipitation every month of the year
     • Low average temperatures in winter but never below freezing
     • Summers are warm but not hot
     • WHY?
       • Prevailing South-Westerly winds produce precipitation
       • Surrounding seas reduce summer temperatures
         • Make winters mild
       • Gulf Stream current brings warm water across the Atlantic, warming the air
       • 5 main air masses
         • Polar Maritime is wet and cold, causing cold and showers from the Greenland Arctic sea.
         • Arctic Maritime ic wet and cold, causing snow in winter from the Arctic
         • Polar Continental is cold in winter, hot in summer, causes snow in winter and dry in summer, from Central Europe.
         • Tropical Continental is hot and dry, causing dry summers from North Africa
         • Tropical Maritime is warm and moist, causing clouds, rain and mildness, from the Atlantic

6. Greenhouse Effect

   • Greenhouse gases retain heat from the sun
     • Without them the planet would be too cold to sustain life
       • Solar energy passes through the atmosphere without an effect
         • 1/2 is absorbed by the Earth. The rest is reflected back by the cloud or upper atmosphere into space
           • The other half is absorbed by the ground and radiated into the atmosphere
             • Some is trapped by greenhouse gases
   • Greenhouse gas emission is increasing due to industrial revolutions
     • EG: Deforestation produces CO2
       • Reducing trees lowers Earth's ability to absorb CO2
     • Is predicted to heat the Earth too hot to survive in by 2090

7. Impacts

   • Sea levels rise due to melting ice caps
     • Cause floods
   • Developed countries
     • New species migrate
     • Increased storminess increases erosion
     • Costs pf protecting low lying areas
     • Costs to NHS due to heatwaves
     • Domestic tourism increases
     • More frequent floods
     • Farmers have to alter crops to suit climate
   • Developing Countries
     • Rising sea levels erode swamps
     • Areas more prone to drought
     • Flooding more common
     • Rising sea levels cause land loss
     • Water shortages could lead to famine