Climate and Change
Past Climate Change
Climate is the average weather condition over a long period of time
We can see the climate has changed over the history of Earth by:
- Fossils of plants and animals in regions that are not found today
- Evidence of glaciation that are now ice free today
- Evidence shown from the rocks, showing the climate they were formed today
- Evidence from ice cores, they show the levels of oxygen and carbon dioxide when the ice were formed.
Figure 1: Temperature over 400,000 years:
As you can see from figure 1 you can see there is a direct correlation between carbon dioxide levels and the average temp, this shows that when there is a higher concentration of carbon dioxide present then the average temp will be higher than normal and when CO2 is lower the average temperature will be lower as well.
Figure 2: Temperature over recent times
As you can see from figure 2 there has been a lot of fluctuation (almost cyclical). As at 0 years the average temp was below 0°C, then the average temp grew and by the medieval warm period it averaged 0.4°C, then the temp shrank back down to below 0°C this was known as The Little Ice Age, and now more recently the temperature started growing again.
The Causes of Change
There are many theories proposed on what causes climate change, these theories can vary a lot in time scale length and also to how severe the climate change can be. The three most important climate changes are:
1) Volcanic Eruption
- Large eruptions release a lot of sulphur dioxide and carbon dioxide into the atmosphere.
- This forms a thicker blanket which reduces the sunlight radiation received to Earth, thus making it slightly cooler.
- E.G. Mount Pinatubo, Philippines, was believed to have reduced the average temperature by 0.5°C
- This is a short term theory happens over a few years
2) Sunspot Activity
- Sunspots are darker areas of the sun, they show greater solar activity in those concentrated areas
- They are a medium term length as they have a 11 year cycle
- E.G. There was a reduced amount of sunspot activity during 1645-1715 (Little Ice Age)
3) Changes in the Earth's orbit and rotation (Milankovitch Mechanism)
- Shape of the Earth's orbit changes every 100,000 years from circular orbits to ellipses -- Orbit Eccentricity
- The Earth wobbles on its axis every 26,000 years -- Precession
- The tilt (obliquity) can vary from 21° to 24°
- Put together, these can affect the solar energy received onto the Earth's surface.
Case Study: Little Ice Age
Due to the changing climate, it has had a major effect in famine and harvest patterns. One famous study was the Little Ice Age and due to the North Atlantic oscillation and reduced sunspot activity, it lasted from 1300-1870 and average temperature was at least 1°C below than today.
Impacts from it:
- Baltic sea and the Thames river froze in the winter
- Sea Ice…