climate change

What period are we currently in & what does that mean ?

Quaternary period. Therefore we are in the last 2.6million years of the earth’s history

What glacial period are we in ?

Interglacial (ice melting)

What is the evidence for climate change ?

1. Sea level raising - thermal expansion + ice melting

   • Increased by 19cm since 1900

   • Increased by 1.8mm every year

2. Ice-melting

   • 134 billion tonnes from the arctic

   • 287 billion tonnes from Iceland

3. Ocean temperatures

   • Hottest temp recorded since 1850

4. Species decline

   • Some animals have gone extinct

5. Ice-core samples (did up columns of ice from Antarctica)

   • Analyse oxygen isotopes to determine temperature & greenhouse gas emissions

6. Dendrochronology

   • Study of tree rings - trees grow more in certain climates

7. Cave-paintings

   • Indicate climate at the time

   • Contain animals which have gone extinct

What are the natural causes of climate change ?

1. Solar output

   • Sunspots (caused by magnetic fields) can change the sun’s energy output

   • 11-year cycles

   • Responsible for very little

   • Decline in solar energy since 1970

2. Milankovitch Cycle - changes in the earths orbit

   • 100,000 year cycle (circle → oval)

     • Varies heat thought the year

   • 41,000 year cycle → tilts on axis

     • Exaggerate seasons

   • 20,000 year cycle → wobbles on axis

   • Cause ice-ages very 100,000 years

3. Volcanic activity (Short-term changes in climate)

   • Produce sulphur dioxide which prevent sun’s rays from reaching the earth’s surface

     • In 1991, Mt. Pinatubo :

       • Erupted 40km into the atmosphere

       • Caused a 2-year avg. global temp drop of 0.5. degrees

Explain The Greenhouse Effect ?

Green house gasses trap the sun’s rays within the earth’s atmosphere which increases global temperature

What other factor contribute to global warming ? (Excluding The Greenhouse Gas Effect)

• Deforestation : increases CO2 in the atmosphere

  • Trees - ‘carbon sinks’ absorb CO2

• Cows : produce CH4

  • CH4 is 25% more efficient at trapping heat than CO2

• Agriculture

  • Produces 20% of greenhouse gasses

What are the impacts of climate change ?

• Rising sea levels (1.8mm) : ice melting & thermal expansion

  • Costal areas at risk of flooding

• Changing rainfall : hotter temp = more evaporation

  • Sahel gets less rain

  • UK gets more rain

• Crops dying : hot weather → soil erosion

  • Kills crops → famine

• More tropical storms

  • Provides water temp. above 27 degrees for tropical storms

• Impact on wildlife

  • Changing environments → difficult for wildlife to cope

• War : competition for good land

• Disease : warm & wet conditions are ideal for mosquitoes.

  • More incidence of malaria