1.1.2 Natural Climate Change | Edexcel GCSE Geography: B (1GB0) Revision Notes 2018

Natural Causes of Climate Change

The global climate conditions of the Earth change over time leading to colder and warmer periods
The last 2.6 million years are the Quaternary period when there have been 60 cold periods and warmer interglacial periods
The last ice age ended approximately 25,000 years ago

historical-climate-change-1

Ice core data: changes in temperature over the last 11,000 years

Water vapour: Evaporation from the oceans, seas and plants
Carbon dioxide: Volcanic eruptions, wildfires and respiration
Methane: Emitted from oceans and soils as part of decomposition, termites also emit methane
Nitrous oxide: Soils and oceans

Causes of Natural Climate Change

Cause	Impact
Milankovitch Cycles	Long term changes to the Earth's orbit and position. This changes how much solar radiation the Earth receives The Earth's orbit changes every 100,000 years a more circular orbit leads to cooler periods and an elliptical orbit leads to warmer periods The Earth's tilt varies every 40,000 years and the greater the tilt the hotter summers are and colder the winters are Every 24,000 years the Earth wobbles on its axis and this can affect the seasonal temperatures
Volcanic eruptions	Large scale eruptions lead to vast quantities of ash being ejected into the atmosphere Ash in the atmosphere blocks solar radiation leading to a decrease in temperatures
Sunspot activity	Increased sunspot activity is linked to higher average temperatures
Atmospheric dust and asteroids	Asteroids and meteors entering the Earth's atmosphere may increase the amount of dust which decreases temperatures Large asteroid collisions can cause fires which release CO₂emissions and the dust sent up into the atmosphere can also lead to cooling as dust particles block solar radiation
Ocean Currents	Ocean currents affect temperature, warm currents such as the Gulf Stream lead to warmer temperatures. If these currents shift it can lead to changes in climate

Mean Antarctic temperatures and atmospheric CO2 concentration over the past 200,000 years

Mean Antarctic temperatures and atmospheric CO₂concentration over the past 200,000 years

You will be awarded 1 mark for identifying a natural cause of climate change and a further mark for the explanation.

Volcanic eruptions (1) cause cooling as incoming solar radiation is blocked by volcanic dust (1)
Asteroid collisions (1) can cause cooling as large quantities of ash and dust are kicked up into the atmosphere (1)
Increased/decreased sunspots/solar flare activity (1) cause warmer/cooler periods as more/less solar energy is released towards the earth (1)
Changes in the earth’s orbit / Milankovitch cycles (1) can cause cooling or warming of the earth as the amount of solar radiation received by the earth varies (1)
Volcanic eruptions (1) can lead to a warming of the earth as more carbon dioxide is released (1)

These trap ash, air bubbles and microbes.
- The air bubbles contain CO₂ providing information about past temperatures
- Ice cores give information regarding the climate for the last 2.6 million years

Allows scientists to know which plants were located where
- The climate requirements of those plants can then be used to know what the climate conditions were

Diaries and art: such as paintings of the Thames river frost fairs
- These are subjective and so may be inaccurate

Each ring of the tree shows a year's growth
- During warmer and wetter years trees grow more and so the rings are larger
- Fossilised tree remains enable scientists to examine the climate over thousands of years