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Fluctuations in the Earth's Climate Change Past - Coggle Diagram
Fluctuations in the Earth's Climate Change Past
Oligocene period, 35 million years ago
rapid transition to colder conditions
related to a major reduction in atmospheric greenhouse gases
A summary of fluctuations in the earth’s past climate
Icehouse conditions
Low CO2 levels, low global temperatures and large part of the continental surfaces covered by ice.
Within these periods there are glacial and inter-glacial periods which are on a smaller timescale.
1 Greenhouse conditions
High CO2 levels, high global temperatures and high sea levels.
Long term transition to colder conditions
100 million years ago – Mid-Cretaceous Period
average global temperatures were 6–8°C
higher than today
Sub-tropical conditions extended from Antarctica to Alaska and there were no polar icecaps
atmospheric CO2 levels five times higher than
today’s, lasted for tens of millions of years
the continents had a very different configuration.
55 million years ago – Palaeocene – Eocene Thermal Maximum
short-lived, spike in global temperatures occurred 55 million years ago
average global temperatures peaked around 23-25°C.
The globe warmed 9 to 11°C. Most ecosystems were able to adapt to this.
Glaciation of Antarctica 35 million years ago
largest glacial system on the planet, containing 25–30 × 106 km3 of glacial ice.
transition to icehouse conditions has been explained by changes in atmospheric CO2 and tectonic processes.
Continental drift
CO2 levels dropped abruptly 35 million years ago, from 1000–1200 parts per million (ppm) to 600–700 ppm
Quaternary Glaciation - the Pleistocene Epoch
The Quaternary period spans the last 2.6 million years ago.
Quaternary is cyclical changes of climate with long cold periods (glacials) with shorter, warmer inter-glacials.
Glacials – have lasted for around 100,000 years
Inter-glacials for 10,000 – 15,000 years.
Over the past 450,000 years there have been four major glacial episodes and four inter-glacials. The most recent glacial was known as the Devensian – and it reached its maximum around 20,000 years ago – at this point one third of the continental surface was covered by ice and snow.
In Scotland – ice sheets were up to 1km deep and most of N England, W Midlands, Wales and Ireland were covered by ice sheets.
Gradually as temperatures warmed the ice thinned and retreated and the end of the last ice age was reached 10,000 years BP.
Ocean Currents
vital component of the global energy budget transferring surplus energy from the tropics to the pole
continental drift can modify ocean circulation and energy transfer
happened around 5 million years ago with the formation of the Isthmus of Panema which joined the North and South American continents and closed the gateaway between the pacific and atlantic oceans
this event intensified the Gulf Stream conveying warm surface water from the Caribbean to the North Atlantic
The Holocene – Our present interglacial
90% of the current Quaternary period has consisted of glacial periods. The Holocene, which began at the end of the last glacial (11,700 years ago) is an inter-glacial period.
During the Holocene, with warming temperatures, ice sheets and glaciers have shrunk and sea levels have risen over 100m. This mostly occurred during the Flandrian transgression (coasts recap)
Since then temperatures and sea level have risen to their present level. This period of significant sea level rise is known as the Flandrian Transgression which mostly occurred 11,000 to 6,000 years ago
Short lived episodes of warming and cooling
6,000 years ago temps 1-2 degrees higher
1100 – 1300 – medieval warm period
1550 – 1850 – ‘little ice-age’ – average temperatures fell by 1 degree and winters in Europe were sent into a deep freeze.