Climate Change and its Causes

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  • Created by: em42
  • Created on: 26-04-15 12:46
1. What is long-term (geological) climate change?
It refers to the cycle of ice ages, beginning around 450 000 years ago. Ice ages and the in between interglacials, occurred at almost regular intervals throughout the geological period known as the Quaternary period.
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2. How are ice cores used as evidence for long-term climate change?
Air can be sampled from bubbles trapped in the ice and CO2 levels from the former atmosphere can be reconstructed. During the ice ages, CO2 levels are very low (180 ppm), rising to 280 ppm in interglacials. Current levels are around 384 ppm.
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3. How is pollen from sediment cores from peat bogs used as evidence for long-term climate change?
Pollen grains are preserved in waterlogged peat. Different-shaped pollen grains signify different trees, some of which lived in Arctic conditions (birch) & others in warmer conditions. However, the evidence is incomplete and long sequences are rare.
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4. What is medium-term (historical) climate change?
From 1000AD-1650, there is no direct climate evidence. So, scientists rely on evidence e.g. from paintings, poems, diaries etc. to reconstruct the climate. These suggest that there was a 'Little Ice Age' from around 1500-1800, Thames froze regularly.
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5. How is the pattern of reteating glaciers evidence for medium-term cimate change?
They can be seen from paintings of the Alps, suggesting that their most recent maximum extent was around 1850.
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6. What is one of the best indicators of medium-term climate change?
The thickness of tree rings. In higher temperatures, with more sunlight and abundant precipitation, trees grow well and have thicker tree rings. In colder periods, their growth is stunted.
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6. What is one of the best indicators of medium-term climate change? [continued]
For some trees, such as the ancient bristlecone pines in W.rn.USA, evidence goes back 4 500 years.
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7. What evidence is there for short-term (recent) climate change?
For the last 100 years, there has been quality intrusmental records as well as detailed records of the response of ice sheets & glaciers. The ice sheets of Greenland, the Canadian Arctic & Antarctica are all aerially surveyed and monitored
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8. What are the basic causes of long-term climate change?
Milankovitch cycles (orbital eccentricity, axial precision & axial tilt).
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9. What are Milankovitch cycles?
They are variations in the Earth's orbit around the sun that cause a change in the amount, distribution & seasonal timing of solar radiation. The theory is called astronomical forcing.
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10. What support is there for the teory of astronomical forcing?
The regular pattern of ice ages & interglacials. The actual impact of these changes is enough to change global temperatures by 0.5°C. Records show that ice ages were about 5°C colder than interglacials. The cycles must have been enough to trigger the
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10. What support is there for the teory of astronomical forcing? [continued]
bigger climate changes. Feedback mechanisms (e.g. gretaer reflection of solar radiation from increased snow that has a higher albedo) could tip the Earth into an ice age.
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11. What is said to be the main natural cause of medium-term climate change?
Changes in solar output at timescales longer than the regular 11-year sunspot cycle. Sunspots (intense magnetic storms) have been well recorded over the last 400 years. The Little Ice Age can be linked to a long period of almost no sunspot activity.
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12. How can volcanic activity at a super-volcano scale alter global climate?
Volcanoes eject huge volumes of ash, water vapour, sulphur dioxide & CO2 into the atmosphere which reduces the amountof sunlight recieved at the Earth's surface. Even for a very large eruption such as Krakatau (19th centruy), the temperature changes
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12. How can volcanic activity at a super-volcano scale alter global climate? [continued]
only last 1-2 years. Patchy historical records suggest increased volcanic activity during the Little Ice Age but it is unlikely to be its cause.
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13. What is the cause of short-term climate change?
The unprecedented scale & rate of change is linked to the huge rise in greenhouse gas emissionsand is therefore a direct result of the enhanced greenhouse effect.
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14. What is the enhanced greenhouse effect?
The extra, unnatural, greenhouse effect caused by humans because concentrations of greenhouse gases have grown significantly since pre-industrial times.
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Card 2

Front

2. How are ice cores used as evidence for long-term climate change?

Back

Air can be sampled from bubbles trapped in the ice and CO2 levels from the former atmosphere can be reconstructed. During the ice ages, CO2 levels are very low (180 ppm), rising to 280 ppm in interglacials. Current levels are around 384 ppm.

Card 3

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3. How is pollen from sediment cores from peat bogs used as evidence for long-term climate change?

Back

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Card 4

Front

4. What is medium-term (historical) climate change?

Back

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Card 5

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5. How is the pattern of reteating glaciers evidence for medium-term cimate change?

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