(During Geological, Pleistocene, pre-historical and historical)
1. Cretaceous period (137-67 m (million) years ago): It had warm moist climate and it helped in spreading of Gileyaequator, to high altitudes. The Indian peninsula not yet hitting Himalayas, Asia and causing disc of was separated by more than 700-800 km wide sea. This reduced temperatures in the tropics by 3ºC and correspondence increase in high altitudes temperatures was also 3ºC.
2. Paleoqene or Palecene period (67-60m. years ago): It marked the beginning of gradual cooling of earth’s surface. Humid forests extend to 47 degree N, against 20ºN of the present.
Cold resistant tropical forests now extend to 32ºN, where as during this period they occupied most of the Europe.
Savannas which now are situated 8 o to 18ºN, existed between 35o and 52ºN. The coal field in Raulkot series belong to this period.
3. Eocene period (60-37 m years ago): During this period climate was still warm and wet. Savannas with spare tree growth developed in Saharan, Arabian, Irani Baloachi and Rajasthan deserts, Sindh was part of these Savannas as and Sahran and Rajasthan deserts joined together in Sindh.
4. Oligocene (37-26 m. years ago): During this period there was progressive fall in temperature. Savannas stretched across whole of Sahara, and Rajasthan desert and also to Eastern Deccan.
5. Neogene i.e Oligocene to Pliocene: during this period, earth surface temperatures further dropped by 8ºC.
6. Miocene (26-12 m. years ago): During this period anthropoid apes (pongids), orang-out-dangs, gorillas, chimpanzees and hominies appeared in ever-green forest remains of 15 apes have been found from Siwaliks.
7. Pliocene (12-4 m. years ago): High pressure developed at 30º North and South altitudes. Monsoon circulation developed. Permanent deserts developed in the tropical and subtropical zones. To the north of these were steepest and to the south Savannas.
8. Eopleistocene (4-1 m. years ago): In the upper Eopleistocene (4-1.5 m. years ago), ancestors of hominids left forests in search of food in Savannas and tried to walk erect. Man also appeared then. Australopithecus who had separated from other hominids then, became extinct some time probably in second part of Eopliestocene (2-1.5 m. years ago).
Ramapithecus, having brain of 600 cms could not be classified as man, because of a low skull volume, (700-800 cms) being dividing line between man and ape and also because he did not use any weapons but used his hands and teeth.
Ramapithecus disappeared prior to ground 1.0 million years ago. Man is not more than 1 million year old.
9. Pleistocene (1.0.8 m. years ago to 10,000 [ya]: The lower Pleistocene (1 - 0.4 m. years ago) is characterized by further drop in temperature and reduction in aridity in the tropics and during 800-600 thousand years ago man developed shell or Abberivillian culture of Archanthropus i.e the following:
Pithecanthropus. In Java.
Sinathropus. In China.
Atlanthropus. Mauritania.
Zeidielburg Pithecanthropus. In Western Europe.
Old wan Pithecanthropus. In East Africa.
The volume of their brain was over 2000 cm2 being twice that or Ramapithecus, Australopithecus and Pre-sinjuncthropus.
10. 600-400 thousand years ago: There was further drop in temperature. The average temperature in the plains of Northern Europe was 5-6ºC lower than it is today and flaciation started. In the tropics and subtropics it was wet.
11. End of (Likhvin) glaciations: At this time developed the paleoanthropus or Neanderthal man using improved tools, hunting and food gathering. His brain cavity was 1450 cm3.
12. Middle Pleistocene (400-120) thousand years ago: Fire and clothing from skin were protected man against cold.
13. 220-120 thousands years ago or danieper Glaciations (Rise, Illinois): Existence of a 100 m thick glacier on Khirthar range between Dad and Gaj river is possible.
14. Upper Pleistocene or late Paleolithic, 120-100 thousand years ago: Inter glacial period lasted from 120-70 thousand years.
Neanderthals developed division of work according to sex, age and domestication of animals. Permanently wet warm climate produced rich flora and fauna and the evolution of material culture was slow.
15. 70-10 thousands years ago or Wisconsin glaciations: The man reached maximum stage of development 15,000 years ago. He developed tribal system.
The cultural changes in man were as under:
- Neanderthal man and Aurignacian - 70,000-40,000 years ago.
OR
- Cro-Magnon man - 40,000-25,000 years ago.
- Solutrean man - 25,000-15,000 years ago.
- Development and presence of modern man
42,000 years ago in Southern Africa.
39, 000 years ago in Kalimantan Island.
38,000 years ago in Poland.
35,000 years ago in France.
36,000 years ago in Australia.
15,000 years ago is South America.
Average span of life of man was not more than 40 years. Pal-eolith is characterized by mud huts, surface dwelling of animal-bone and wood and cloths sewn from animal skins.
Ice cap receded and melted by 10,000 years age.
16. Holocene 10,000 years ago to present day: An early Holocene or Mesolithic (12,000-7,000 years ago) is characterized by:
- Primitive community system ended.
- Material family (material chate) ceased.
- Parental family started.
- Slave owning society began to take shape.
- Pottery production arose.
- Cooking of food became systematic.
- Cattle herding developed.
- Agricultural production introduced and developed.
- First cultivators were women, who used simple stick to make furrows to cultivate cereals.
- Men did hunting and tending cattle.
a) Neolithic (7,000 – 4,500 years ago).
b) Bronze Age 6,000 – 4,000 years ago.
c) Woven fabric 4,000 BC in summer in Mesopotamia.
17. Climate changes in Middles Holocene: Tundras were limited to North Siberia etc.
18. Middle Ages; 500 to 1600 AD: This is characterized by:
- Simple machines using power of
- Man.
- Animal.
- Water.
- Wind.
19. Modern times: 1600 – to-date in Sindh and 1380-1850 in Europe: It is characterized by:
- Harnessing of power from fuels.
- Capitalistic power rise and colonization.
20. 1200-1300 AD: About 2o or 3ºC displacement of latitude due to physio-geographical process from earth’s mean, also caused climatic changes.
21. Little Ice Age 1500-1700 AD: in 17th century a drop of 1 to 2ºC in average temperature brought about “Little Ice Age”.
22. Climatic patterns of past 500 years and causes of it: Taking climate of 45 years average from 1900 to 1945 and again climate of past 500 years, it was cooler before 1900 AD and also cooler from 1945 to 1990, the results are:
Between 1800 AD and 1940 difference is 0.6oC rise and between 1945 to 1990 it is a fall of 0.3ºC.
23. Causes of climatic change: Mean global temperature 18,000 years ago was 6ºC cooler and British Isles were under rice. It was the height of last glaciations.
- In deserts and poles, earth receives less radiation than it returns, but at equator it receives more than it returns.
- No part of weather system, can be dissociated from the other. Orbit of the earth around sun varies between 90,000 – 100,000 years. It is some times almost circular and at other time elliptical.
- When it is elliptical, solar radiation varies 30% during the course of the year.
- Today it is at 70º tilt on it oscillation around the sun.
- Greater the tilt more is difference between summer and winter temperatures. Last maximum was 10,000 years ago.
- Earth wobbles around its axis, cycle takes 21,000 years.
- Sun also rotates and cycle varies from 90 to 27 years.
- Sun spot cycle of 11 to more accurately 22 years is most famous.
- Sun spots having 22 years cycle vary and cause variation in the solar radiation there by climate on the earth. Between 1645–1715 AD, radiation could have been 1.4% lower than at present and there by there was difference of 1 to 2ºC. Radiation increased around 1916 AD. Differences between rotations of planets including earth, has disturbances on sun, at a rhythm of about 1700 years. Pull of earth and sun creates tides. Exceptional high tides occur at 1800 year interval patterns, and set a process in train, which takes long time to correct. The Little Ice Age may have been triggered by tidal maximum altitudes in 1433, which caused south ward drift in the polar ice and it on-set “The Little Ice Age”.
24. Climatic changes in the historical times. Four climatic Epochs since 12,000 to 10,000 BP: These changes were world-wide and in Sindh they are represented by the following:
i) Warm times 5000-3000 BC.
ii) 2900-300 BC, colder.
iii) 3090 BC – 1430 AD, warm.
iv) 1430 – 1850 cold.
v) 1850 – 1940 warm.
These are further explained as:
a) Warmest times culminating 5,000 – 3,000 BC. Between 5,000 – 3,000 BC, sea level rose rapidly as former great ice sheet kept melting after ice age. Sea kept rising further up to 2000 BC, when it may have been 3 meters higher than to-day. Between 5,000,000 BC, temperatures were higher in Europe by 2-3ºC than the present. The same was the case with Antarctic. Temperature in Sindh may have been higher by about 1 to 2ºC.
b) Colder climatic epoch of Iron Age culminating or reaching its maximum 900 BC. After 900 BC, colder period started and even upto 300 BC, it was cold.
c) Rise of Indus civilization 2300 – 1700 BC, was quick and decline was caused by drought after 2000 BC.
d) In the Southern Hemisphere 5000-3000 BC, was a cold period as per available data.
e) Around 100 BC, Italy witnessed warmer times than centuries preceding it.
f) Dust storms are recorded in the 8th century AD, which may have affected Brahman rule.
g) Rangmahal culture occupied the Indus region in the 4th century AD, showing better rainfall. The construction of stupas from 5th to 7th century in Sindh also show prosperity due to climatic change.
h) Warmest of Early Middle Age was 1000-1200 AD, Temperature started rising and optimum was reached around 1000-1200 AD. Some investigators are of the opinion, that temperatures were quite favorable in Sindh, even after 800 AD, in the northern America. The above optimum shows, the rise of Habaris and the Soomra of Sindh. The above optimum was also wetter period in America. 900-1120 AD, were a warm, though variable times. The deserts are reported to have expanded around 1000 AD, but statement is not fully verified for Sindh.
i) India witnessed a number of famine years in the 14th century.
j) Little Ice Age 1430-1850 AD, in Europe and 1500-1700 AD, in Sindh and England in late 16th century. It had its maximum effect in Sindh from 1600-1700 AD. Cooling had probably began around 1130 AD, and 1380 AD, its impact was perceivable in Central Asia and India.