Climate change

Climate change

1. Climate change is the long-term change in the weather

   • Global climate change occurs very slowly over thousands of years
     • The earth's surface temperature has increased by approximately 1 degree over the last 100 years

2. Evidence for climate change

   • Ice cores
     • Layer upon layer of compacted snow and ice contain information about temperature and gases
       • Oxygen isotopes in the ice cores are commonly used to estimate what the temperatures would have been
       • When the ice cores are melted trapped carbon dioxide and methane are released
         • Can be compared to current levels to see the difference in climate
   • Graphs
     • Keeling curve
       • Shows the increased level of CO2 in the atmosphere
     • Hockey stick graph
       • Shows the increase in the earth's temperature over the last 1000 years
     • The increase in CO2 is almost identical to the temperature increase
   • Melting ice sheets
     • Melting will affect the salinity of the oceans which will affect the currents
       • This could stop the Gulf Stream which currently heats the UK
   • Glacier retreat
     • Melting due to rising global temperatures causing them to retreat
       • E.g. Patagonia - Uppsala glacier
   • Changing weather
   • Sea level rise
     • Due to warmer temperatures- the oceans will expand
     • Ice sheets melting from the land

3. Causes of climate change

   • Natural phenomenon
     • Climate change has been happening throughout the Quaternary period, before humans were present on the planet
       • Long-term climate change is a result of natural causes
     • Solar output
       • Measured by observing sunspots on the Sun's surface
         • Sunspots- caused by magnetic activity inside the Sun which results in dark patches on the surface
       • Output increased slightly from 1900 to 1940 but has barely changed in the last 50 years
         • Solar output cannot be responsible for the cause of climate change seen from the 1970s
     • Orbital changes
       • The distribution of the sun's energy on the Earth changes due to the earth's orbit
     • Volcanic activity
       • Eruptions can temporarily cause climate change
         • When sulfur dioxide mixes with water vapour it becomes a volcanic aerosol
           • Reflect the sunlight away and reduce the sun's heat energy entering the atmosphere
   • Enhanced greenhouse effect
     • Greenhouse effect - naturally occurring phenomenon that keeps the earth warm enough for life to exist
       • The natural layer of greenhouse gases traps some of the sun's infrared heat
     • Human activity has increased the layer of greenhouse gases which naturally exists
       • Fossil fuels
         • Account for the majority of greenhouse gas emissions
         • Burning these releases carbon dioxide into the atmosphere
         • As the world's population grows and wealth increases people are demanding more and more energy which increases the level of fossil fuels and carbon dioxide
       • Agriculture
         • Contributes to approximately 20% of global greenhouse gas emissions
         • As the world's population increases more food is required which will increase the release of greenhouse gases
         • Large amounts of methane
       • Deforestation
         • Leaves fewer trees to absorb carbon dioxide
         • Stored carbon dioxide also released when trees are burned

4. Managing climate change

   • How can the causes of climate change be reduced?
     • Alternative energy production
       • Renewable energy sources
         • E.g. Wind, solar, geothermal, wave and tidal and biomass
         • More expensive (but becoming cheaper) but don't produce CO2
       • Solar energy
         • In 2013 15% of the UK's electricity was generated by renewable energy sources
         • A typical home saves a tonne of CO2 per year as there are no greenhouse gas emissions to contribute to climate change
         • However can't be relied on to produce electricity all the time such as at night
     • Carbon capture
       • Captures CO2 from emission sources and stores it safely
         • Can also remove CO2 from the open atmosphere by converting it into anliquid
           • It is then injected into sedimentary rock
       • Can be used with existing and new power plants and could provide 10 to 55% of the world's total mitigation until 2100
     • Planting trees
     • International agreements
       • UN negotiated a new international climate change agreement for all countries at the 2015 Paris climate conference
       • European Commission - reduce global emissions by at least 40% below 2010 levels by 2030 and 60% by 2050
   • How can climate change be managed through adaptation?
     • Change in agricultural systems
       • Moving production to another location due to changing temperatures and extreme weather
       • Changing crops and varieties grown and the time of year they are planted
     • Managing water supply
       • Reducing demand
         • By 2030 all of London homes should have been offered a retrofit package of water-efficient devices
         • Water Strategy to reduce London's water demand
       • Increasing supply
         • Thames Water opened a desalination plant in 2010
           • Water is taken from the Thames at low tide (least salty)
           • Reverse osmosis produces drinking water for 400,000 homes
     • Reducing risk from rising sea levels
       • Thames Barrier to stop tidal surges entering London