•Ayesha Maqsood•Fareeha Aftab•Hira Sattar•Madiha Ramzan•Maryam Habib•Sundas Waheed

CONTENTS: Introdution Climate change in past years. Pre-Holocene (1.5 million years) Time scale its Event and Climatic

conditions Five Perspective of climate change Evidences and records Conclusion.

INTRODUCTION:

A millennium – Latin word “mille” means thousand. 

Is a period of time equal to one thousand years.

The term refer to an interval of time beginning on any date.

Climate change:

The earth climate has been changed throughout history.

Just in the last 650,000 - seven cycles of glacial advance and retreat

Causes: very small variations in Earth’s orbit change the amount of solar energy

our planet receives. The current warming trend is of

particular significance because most of it is very likely human-induced.

Pre-Holocene(1.5 M.years) 15,000 BC to 5,000 BC - time of

transition, and swift and extensive environmental change.

Planet was moving from an Ice age, towards an interstadial(warm period). 

Sea levels rose dramatically. Land that was depressed by glaciers

began lifting up again Forests and deserts expanded. and the climate gradually became

more modern.

Warming Process lead to:

“cold snaps” and “warm snaps”- Older Dryas and the Holocene climatic optimum

Heavier precipitation. The Pleistocene megafauna became extinct

due to environmental and evolutionary pressures from the changing climate.

11,700 years ago (9700 BC) is widely - end of the old age (Pleistocene, Paleolithic, Stone age, Wisconsin Ice Age), and the beginning of the modern world as we know it.

Some major events and climate changes:

19000 BC: Last Glacial Max, Sea level Min.

17000 BC: Oldest Daryas stadial, glaciation in Europe.

12000-11700: Oldest Dryas stadial 13000-11000: Melting of glaciar, Lake Agassiz form.Floods into Arctic Ocean 10800: Younger Dryas begins. 10000: Sea level rise, FloodingEnd of most recent Glaciation.

10th Millennium:(9700-9000BC) Lake Agassiz reforms from glacial

meltwater Bering Sea: Land bridge

from Siberia to North America disappears as sea level rises.

Younger Dryas cold period ends. Pleistocene ends and Holocene begins.

The Younger Dryas as stretching from 10,800 BC to 9500 BC. This cool period was possibly caused by a shutdown of the North Atlantic thermohaline circulation (Gulf Stream/Jet Stream), due to flooding from Lake Agassiz as it reformed.

End of the pre-Boreal period of European climate change.

Temporary global chilling, as the Gulf Stream pulls southward, and Europe ices over (1990 Rand McNally Atlas).

In Antarctica, long-term melting of the Antarctic ice sheets is commencing.

9th millennium BC8500-800BC Last glacial period ends. Long term melting of Antarctic ice

sheets. Rising sea levels in Asia Wisconsin glaciation had withdrawn

completely in North America. Due to glacier melting, Inland

flooding occur.

8th millennnium BC7900-3000BC Lake Agassiz refills due to glacial

retreat north Neolithic Subpluvial begins in

northern Africa. Untill about 500BC, the Sahara

Desert is wetter than today.

7th millennium BC6600-6000bc Kurile volcano on Russia’s Kamchatka

has erupted. A sudden cooling episode was occurred. The Storegga Slide causing a

megatsunami in the Norwegian Sea. Rising sea levels from the Torres Striat,

separate Australia from New Guinea. Increasing desiccation of the Sahara. Rising sea levels from glacial retreat

flood will become the Irish Sea.

6TH MILLENNIUM BC5600-5000BC The Black Sea floods with salt water. Desertification lead to the creation of

Sahara Desert. A global warm period begins.

4TH MILLENNIUM BC3900-2800BC

Intense Aridification triggered worldwide migration to river valleys

Return of extremely hot and dry conditions in Sahara Desert

Burckle Crater is formed in Indian Ocean

3rd Millennium BC

Floods at Shurupak stretching as northern Kish, as far as south Uruk, associated heavy rains Nineveh.

Sahara becomes fully dessicated. Severe Droughts in nouthern Africa ,

Southwestern Asia and mid-continental North America.

2nd Millennium BC1900BC-1000BC

Babylonian flood… Evidence of major droughts Eastern

Mediterranean.. Sarasvati river dries up…

Desertification in thar region begins

1st Millennium Bc800-200BC Sub Atlantic sea level rise. Cooler and more humid climates ,and

dominance of beech forest.

1st Millennium AD

1st century(year 79 AD) Mount Vesuvius erupts ..

Pompeii and cities affected by eruptionPompeii located around base of volcano..

2nd century

Eruption in newzealand…

6th Century(year 535- 536)

Global climate abnormalities.. These changes were due the ashes or

dust thrown into air after impact of comet or meteorite, or after eruption of valcano..

9th century (Yr :850)

Severe drought exacerbated soil erosion as the result of which the central america collaps.

13th century (1250-1850)

Little Ice Age starts a stadial period within our interglacial warm period

15th century (1453)

Eruption of kuwae in pacific. Environmental science developed.

17th century (1600) Huaynaputina erupts in south

america. Effects the climate of the northern

hemisphere. 1601- coldest year famine in russia.

18th century (1759-1789)

The volcano Laki erupts. Sufficient SO2 and sulphate

particles- unusual cold winters in europe and western asia.

19th century (1815-1883)

Eruption of MT. Tembora- now indonesia.

Year Without Summer in N America and Europe.

Eruption of Krakatoa in Indonesia. The sound of the explosion is heard as far as Australia and China, the altered air waves causes strange colours on the sky and the volcanic gases reduce global temperatures during the following years. The vivid sunsets were captured in Edward Munch's The Scream

Temperature changes due to different forces

Major climatic events that occurred in last decade: The summers of 1994 and 1995 broke quite

some heat records e.g 24 °C recorded on south-east Greenland!

The Typhoon Faxai in December 2001, in the West Pacific, of over 285 km/h, gusts of 350 km/h and a central pressure of 879 mbar.

In the year 2005 the US were hit by two strong hurricanes: "Katrina" and "Rita"In 2010 Pakistan was hit by the largest disaster since its independence. Major floods, due to extreme monsoon rains, in the Indus valley affected more than 20 million people

A. The astronomical perspective1. Brightness of the sun:

The climate can be influenced by solar energy caught by the Earth.

During the lifetime of the Earth (the past 4.5 billion years) the sun became 25% brighter.

Modest variation of the energy output (0.05 - 0.1%) of the sun.

Correlation between weather patterns and the sun spot cycle.

During the climax of the "little ice age" (1645-1715) there will be very little sun.

The rise in solar irradiance since 1750 is estimated at 0.1 - 0.5 W/m2 (0.04 - 0.2%)

2. The orbit of the Earth Milankovitch - study on the relation

between the orbit of the Earth and its climate in the last 2 million of years.

The following variations occur in the orbit and orientation:

The eccentricity varies by 6% with a 100.000 year period. This gives rise to a 0.3% variation in solar heat flux.

The obliquity of the Earth varies between 21.8° and 24.4° with a period of 41.000 year.

The precession of the Earth's axis has a period of 25.800 year.

B.The geologic perspective 1.Continental drift and oceanic

circulation patterns The positions of the continents and

the resulting ocean circulation. The higher amount of CO2 in the

atmosphere. (maybe to a lesser extent)

The Earth is oscillating between an extreme greenhouse state and a totally frozen state. It evolves as follows:

1. Continents gatherered around the equator. Increased rainfall on the equatoral continents leads to weathering, and a falling CO2 content.

2. The albedo of the Earth rises drastically, and a run-away icehouse effect occurs. The Earths' Oceans freeze over totally, and the temperature drops to -50 °C.

3. Volcanic activity, bringing CO2. Earths' temperatures raise enough, melting the ice in the equatorial regions.

4. The ice melts quickly. The decreased albedo, combined with CO2 content of the atmosphere, causes the T to soar upwards to 50 °C.

2. Volcanism:Earth quite spectacular volcanic events

have occurred. Two examples are the formation of the "Siberian traps" during the last stage of the formation of the supercontinent Pangea (-245 Myr) and the formation of the "Deccan traps" north-east of Bombay, when India was on its way to Asia (-65 Myr). In both cases 1 to 1.5 million cubic kilometers of basaltic lava was erupted in less than 1 million years

C. The greenhouse gases' perspective The atmosphere contains greenhouse

gases. Without the presence of these gases the Earth would be as cold as -18 °C in average.

The main greenhouse gases are: Water vapour, CO2 CH4 N2O CFC's.

D.The weather patterns perspective

D.The weather patterns perspective

1.The location of ice caps After the climax of the last "glacial"

18.000 years ago, the climate recovered. The ice caps on Scandinavia and Canada

were dwindling rapidly. The climate in Europe in those days was

about as warm as it is today.E. The role of sea currents1. The Atlantic Gulf Stream (and the

little ice age)The Atlantic Gulf Stream has a profound

influence on the climate of Europe.

Eastern sides of oceans in winter are much warmer than western sides of oceans

2.El Niño and the southern oscillation

Every few years the air pressure rises in the western Pacific and drops in eastern Pacific. As a result the trade winds are weakened. Sometimes the easterly winds on the equatorial zone are replaced by western winds.

Sources of information on the climate change include:

Sources of information on the climate change include: Historical documentary records, Tree rings (width, density); Ice cores (isotopes, melt layers, net

accumulation, glaciochemistry); Corals (isotopes and other

geochemistry, growth rate); Varved lake and marine sediments

(varve thickness, sedimentology, geochemistry, biological content)

Banded speleothems (isotopes). Microfossils records.

Volcanoes and Climate Tree-Rings Records of Volcanic

Activity

A list of years characterized by low tree-ring densities, with the name of the volcano eruption immediately preceding the tree-ring event indicated in parentheses

Sun Cycles and Climate Change

Conclusion