Natural causes of climate change
1) The sunspot theory
The output of energy from the sun varies, when the sun has lots of sunspots on its surface, it is giving out more energy
There are links between years with low solar output and colder temperatures.
2) The eruption theory
Volcanic eruptions produce ash and gases that affect the way heat and light reaches us on earth.
If ash and gases rise high enough, they an spread around the earth in the stratosphere.
Therefore this will stop some light reaching us, cooling the temperature.
Sulphur dioxide>Sulphate aerosols>Reflect solar radiation>absorb radiation reflected from earth
Natural causes of climate change
The Orbital Theory (milankovitch cycles)
1) Shape of the orbit (eccentricity)
elliptical or round, this alters the distance from the sun and therefore the temperature of the earth
The tilt of the axis changes from 22.5 degrees to 24.5 degrees. The tilt can alter temperature and precipitation. Tilting away from the sun is colder, towards is warmer.
3) Wobble (Precession)
The earth wobbles on it's axis. 23,000 years cycle. This alters the distance from the sun, thus climate.
Evidence for a changed climate
Evidence showing that climate used to be different:
- Samples from ice sheets of Greenland and Antarctica
- Lanforms such as the U-shaped valleys left, as a result of retreating glaciers
- Fossilised animals, plants and pollen that no longer exist in the UK
- Newspaper articles
- Old photos and drawings
- Recorded dates of harvest, blossom and bird migration.
The Little Ice Age
- 'Erik the red' and approximately 500 other vikings found Greenland, which at the time was free of ice.
- by 1100, Greenland had
- over 200 farms (goats, sheep, cows etc)
- 3000-4000 vikings
- Trade links with Iceland and Norway
The vikings survived over 4 centuries
- De-forestation lead to soil erosion, meaning that the viking farms produced little food.
- The vikings were too dependant on trade with Norway and Iceland, when the sea ice stopped the trading, this became a problem
- They did not adapt to their environment
Effects of Climate change on Ecosystems
65 million years ago, many dinosaurs suddenly became extinct. Two possible causes are
- A strike by a massive asteroid in Mexico
- A huge volcanic eruption in India, lasting up to 1 million years
Both of these possibilities lead to the cooling of the earth, thus plants struggled to survive, breaking down the food chain
Mega fauna- big animals, over 40kg, e.g woolly mammoth, ground sloth etc
When the last major ice age ended, animals migrated to a climate in order to find suitable food. However, this disrupted food chains, and it was difficult for these animals to find suitable food in a new climate. Humans also hunted mega-fauna for tusks and goods. As a result, many species became extinct.
Effects of Climate change on an LEDC
- could lead to floods. As a result of the floods, crops are destroyed and farmers experience a lack of income, leading to hunger.
Higher temperatures- temperatures have risen by 2.3% since 1970
- This would mean that traditional crops are not suited to this climate, meaning these crops would fail, leading to hunger. In addition, farmers would have to change their types of crops which could cost more to farm, giving a lower profit.
Shorter rainy season
- could result in not enough water for crops, a fall in yields and less money.
- It could also lead to the community travelling further for water, and therefore having less time for education or tending crops.
Effects of Climate change on an MEDC
Costs of a warmer UK
- Drought and water shortages in the summer, especially in the South
- More illnesses such as skin cancer and heat stroke
- Farmers might have to change crops to ones that need less water
- Some species could die out
Benefits of a warmer UK
- Heating costs could fall in the winter
- More people could take Holidays to the UK, bringing money to the tourism industry
- New crops could bring new opportunities for farmers.
The UK could experience more heatwaves, flooding and storms, causing more economical damage to property. This weather is difficult to predict.
National- The Stern Review
- written in 2005, the report was commissioned by the British Government to study the economic effect of climate change
- It recommended that we spend 2% of GDP reducing GHG pollution
- It warned that the effects of global warming could reduce our GDP by 20%
- the poorest will suffer the worst
International- Kyoto Agreement
- Kyoto protocol
- 181 countries signed to reduce emission by 5.2%
- It has put climate change on the worldwide agenda for government
- the effects of global warming will be felt polluting and non-polluting countries, therefore an international agreement is needed
The Greenhouse Effect
The greenhouse effect is a natural process. Without it, the earth would be unable to retain enough heat to sustain life.
The enhanced greenhouse effect is caused by GHGs that are emitted from burning fossil fuels and agriculture. These all trap more heat and radiation from the sun than is normally required. The earth radiates infrared energy from the sunlight that reaches the surface which should escape off into space, but due to the enhanced greenhouse effect, this radiation is trapped. Therefore, the overall temperature of the globe rises.