4.1: The cause of longer and short-term climate change Flashcards
Where is there identifiable evidence of glaciation within Europe?
The North European Plain
How can ice cores be used to determine past climate events?
And what does their contents indicate?
Air bubbles trapped within the ice contain atmospheric carbon dioxide and the ice itself proves a record of oxygen isotopes - low contractions of carbon occur during glacial periods whereas much higher ones indicate an interglacial period.
When did the Quaternary period begin?
2 million years ago
Why did the tertiary period end?
there was an onset of global cooling and ice-house conditions
What is a glacial period?
cold, ice-house period within the Pleistocene
what is an Interglacial
Warner periods similar to the present, i.e greenhouse periods
what are Ice-house conditions?
very cold gacial conditions
what are Green-house conditions
much warmer interglacial conditions
Quaternary period is divided into 2 epochs of geological time. Name them.
Pleistocene and Holocene
Describe the span of the Pleistocene period
covers the time span from the Quaternary to 11,500 years ago when the most recent continental glacial ended
Describe the Holocene period
interglacial period (we are living in now) is similar climatically to previous interglacials, but is distinctive a it is noted for the growth of human civilisation
Glaciers and their meltwater to create erosional and depositional features. But can these be changed over time?
And how does this affect scientists ability to understand glacial process’
landforms produced have been changed by later glaciations and post-glacial geomorphic processes making reconstructing past patterns of glaciation challenging.
Define what a Stadial is
colder periods that lead to ice re-advancement
Define what an Interstadial is
short term fluctuations within in ice-house-greenhouse conditions
Name the three elements of the Milankovitch cycles
- Eccentricity
- Axial Tilt
- Axial Precession
Explain Eccentricity and the timescale in which it happens
state how this affects global temperature
The orbit of the earth changes from elliptical to circular and back again over a period of 100,000 years. This changes the amount of radiation received from the sun to the earth due to the changes in distance between them
Explain Axil Tilt and the timescale in which it happens
state how this affects global temperature
It varies from 21.8 to 24.4 degrees (currently the earth is tilted at 23.5) over 41,000 years. This changes the intensity of sunlight received at the poles and, therefore, the seasonality of the earth’s climate. The greater the tilt the greater the difference between summer and winter.
Explain Axil Precession and the timescale in which it happens
state how this affects global temperature
The earth wobbles on its axis changing the point in the year at which the Earth is closest to the sun over 21,000 years. This causes long-term changes to when different seasons occur along the earth’s orbital path.
Change in orbit are impactful to global climate however by how much do these changes change global temperature?
0.5 to 1 degrees
What are climate feedback mechanisms?
Describe them both and what affect they have
Feedback effects are those that can either amplify a small change and make it larger (positive feedback) or diminish the change and make it smaller (negative feedback)
Does positive feedback increase or decrease warming or cooling rates?
Increase
Does negative feedback increase or decrease warming or cooling rates?
Decreasing
Explain 2 factors of positive feedback and their effects
Hint: to do with snow and ice cover
- Increase in snow and ice cover
Small increases in snow/ice cover raise surface albedo (reflectivity) so more solar energy is reflected back into space leading to further cooling, which can lead to further snow and ice cover - Melting of snow and ice cover
The melting of snow and ice covered by CO2 emissions decreases albedo. Methane is emitted as permafrost melts and warming seas lead to calving of ice sheets, which all lead to loss of snow/ice cover and surface albedo decreasing reflectivity and accelerating further warming
Explain 2 factors of negative feedback and their effects
Hint: to do with snow and ice cover
- Global dimming
Increase in global warming leads to more evaporation and, over time, pollution from industrialization adds to global cloud cover. Increaly cloudy skies could reflect more solar energy back to space and diminish the effect of global warming - so may become less intense because of this global dimming - Thermohaline Circulation
Ice sheet dynamics can disrupt the thermohaline circulation (THC). warming water in the arctic disrupts ocean currents; less warm water from the gulf stream is drawn north, which could lead to cooling in europe - therefore slowing down the effects of global warming
What is the thermohaline circulation system?
a global system of surface and deepwater ocean currents driven by differences in temperature (thermo) and salinity (haline) between areas of oceans. Sometimes called the ocean conveyor.
How do solar sunspots affect global temperatures?
The amount of energy emitted by the sun varies as a result of the number and density of sunspots (dark spots on the sun’s surface caused by intense magnetic stores). The more sunspots there are and the more intense they are the greater the rise in global temperature
2 historical examples of the impacts of solar sunspot
- A longer period with no sunspot activity, the Maunder Minimum, occurred between 1645 and 1715, at the height of the Little Ice Age
- The proceeding mediaeval warm period has been linked to more intense sunspot activity
How does Volcanic Activity affect global temperatures?
Violent volcanic activity can alter global climate.
Eruptions with high volcanic explosivity index (VEI) eject huge volumes of ash, sulphur dioxide, water vapour and carbon dioxide into the atmosphere (volcanic aerosols), which high level winds distribute around the globe
2 historical examples of the impacts of volcanic activity affecting global temperatures
- In 1815 Tambora in Indonesia ejected 200 million tonnes of sulphur dioxide into the atmosphere and for the following three years, temperature were recorded 0.4-0.7 degrees lower - so short lived global cooling occurred
- Laki Fissure eruption in Iceland from 1783-84. The size of volcanic aerosol and length of the eruption were linked to the exceptionally cold winter in the northern hemisphere in 1785 - (which contributed toward the French revolution)
Describe the Loch Lomond Stadial
State when it happened, the change in temperature it caused, its effects and what caused it?
- Around 11,500 years ago glacial conditions occurred
- Temps 6-7 degrees lower
- Glacial re-advancement occurred in many parts of the world; formation of ice caps in the Scottish highlands, from which cirque and valley glaciers flowed. Smaller areas of cirque glaciers formed in the lake district and north wales
- One possible cause was the drainage of the huge proglacial lake Agassiz disrupted the THC, thus cutting off the poleward heat transportation from the gulf stream
Describe the Little Ice Age
State when it happened, the change in temperature it caused, its effects and what caused it?
- Between 1350 and 1900 conditions were slightly colder - on average 1 - 2 degrees - than at present
- Between 1550 and 1750 there was a low trough of very cold conditions causing the little ice age
- Widespread abandonment of upland farms in scandinavia and iceland
Arctic ice sea spread further south with polar bears frequently seen in Iceland
Rivers in the UK, lowland europe and the New York Harbour froze over
Researchers argue that the little ice age could have developed into a stadial but this was prevented by the industrial revolution, fired by coal. The release of C02 triggered climate warming, which halted the cold period.
