Climate Change

  • Created by: chebarnes
  • Created on: 18-05-18 09:34
Sea-floor sediments
Fossil shells of tiny sea creatures called 'foraminifera'. - can be used to reconstruct past climates because the chemical composition indicates the ocean temperatures in which they were formed.
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Ice Cores
From the polar regions, contain tiny bubbles of air - Scientists can measure the relative frequency of hydrogen and oxygen atoms with stable isotopes... The colder the climate, the lower the isotope frequency.
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Lake Sediments
Pollen grains, spores, diatoms and varves in lake sediments. Identifies past vegetation types.
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Tree rings
The dating of past events such as CC through the study of tree ring growth (annule). Annules vary in width each year depending on temp conditions and moisture availability.
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Fossils
Can be used as proxies for climate.. analysed to see what animals lived in those conditions.
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Greenhouse conditons
Atmospheric CO2 concentrations, global temps and sea levels = high
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Icehouse conditions
Low global temperatures & large parts of the continental surface submerged by ice. (Opposite to Greenhouse)
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How long did the Pleistocene last for? And what was it?
Interglacial period - lasted for around 1 million years.
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When was the mid-cretaceous period?
~ 100 million years ago
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How much higher were av. global temps in the mid - cretaceous period?
6-8 degrees higher than present day.
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How long did the mid-cretaceous period last?
Tens of millions of years
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Last 2.5 million years known as?
Quaternary period
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How long ago did ice sheets cover most of NW Europe?
20,000 years ago
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Palaeocene-Eocene themal maximum
Spike in global temperatures - Occurred 55 million years ago - Average global temps peaked @ around 23 degrees.
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Oligocene period
35 million years ago - rapid transition to colder conditions, which have continued to the present day
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What was the Oligocene period related to?
A major reduction in atmospheric GHG's (especially CO2)
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Antarctica - 40 million years ago, the fossil record shows that the continent experienced what conditions?
Sub Tropical
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Descent of Antarctica into a permanent icehouse state occurred rapidly when?
35 million years ago
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Antarctica's transition to icehouse conditions due to (1):
CO2 levels dropped abruptly 35 million years ago _from 1000-1200 ppm to 600-700 ppm.
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Antarctica's transition to icehouse conditions due to (2):
Continental drift
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Antarctica's transition to icehouse conditions due to (3):
Growth of the South Sandwich Islands - submerged volcanic arc disrupted deep-water ocean currents around Antarctica, isolating the continent from warmer water from the S Pacific, Atlantic and Indian Oceans.
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External forcings
Astronomical shifts in the Earth's orbit and axial tilt, the precession of the equinoxes and fluctuations in solar output.
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What do the external forcings control?
The incidence and distribution of solar radiation on the Planet's surface.
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Internal forcings
Volcanic eruptions, continental drift, changes in ocean circulation and fluctuations in atmospheric CO2
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Milankovitch Cycles - Argument
Milankovitch argued that long term climatic shifts, eg glacial cycles are caused by astronomical events such as changes in the Earth's axis and orbit and the precession of equinoxes.
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What do the external forcing mechanisms affect regarding solar radiation?
Affect the amount of solar radiation reaching the planet's surface and its spatial and temporal distribution.
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What time scales do external forcing mechanisms work on?
Vary from 10,000 to 100,000 years.
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Obilquity (tilt of the Earth's axis)
Over a period of ~ 40,000 years, the axial tilt varies from 22 degrees - 24.5 degrees (currently 23.4)
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What happens when the Earths axial tilt is close to 22 degrees?
Seasonal temp differences are reduced, i.e summers = cooler and winters = warmer. As a result, snow and ice accumulated during winter, do not melt during the summer, allowing glaciers and ice sheets to expand. - This has a positive feedback effect
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Eccentricity of the Earth's orbit
Follows an elliptical path (around the sun). Varies from near circular to markedly elliptical over periodicities of 96,000 and 413,000 years. Ice ages correspond to periods of maximum orbital eccentricity
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Precession of the equinoxes
Earth gyrates on its axis, so that the point in the Earth's orbit when the planet is closest to the sun changes over time. This shift of precession which occurs with a periodicity of ~ 22,000 years is due to the gravitational influence of the Moon
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What does the shift or precession of equinoxes affect?
Intensity of seasons
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Pangaea
Single Huge Land Mass - 250 Million Years Ago
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Other cards in this set

Card 2

Front

Ice Cores

Back

From the polar regions, contain tiny bubbles of air - Scientists can measure the relative frequency of hydrogen and oxygen atoms with stable isotopes... The colder the climate, the lower the isotope frequency.

Card 3

Front

Lake Sediments

Back

Preview of the front of card 3

Card 4

Front

Tree rings

Back

Preview of the front of card 4

Card 5

Front

Fossils

Back

Preview of the front of card 5
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