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Climate change Climates have changed and still are constantly changing at all scales, from local to global, and over varying time spans, both long term and short term. CLIMATE IS STILL CHANGING EVEN NOW
CLIMATE CHANGELONG INTERMEDIATE AND SHORT TERM TRENDS The atmosphere is constantly changing so it is necessary to make a distinction between genuine climate changes and day to day fluctuations in the weather. Long term and permanent trend will get more attention than temporary variation of a more random nature.
The table show an attempt to classify the temporal and spatial scales and is the approach we will use. Matter of scale can be fundamentally affect our perception of climate change e.g.cooling of the northern hemisphere was noted between 1940 and 1970 was believed as a beginnning of a long term global trendwhich is actually a temporary fluctuation and perhaps it is linked to a number of volcanic eruption including Mt Agung in indonesia in 1963
LONG TERM CHANGES Only a little change has been experience for over millions of year. Most geological evidence suggest that average global temperatures over the last 3 billion years were about 15°c , and over the last million years about 22°c. Both hemisphere does not experience any significant change due to analysis on ice cores from Greenland and Antarctic . Coral fragment had been found in coral stone in Derbyshire and evidence of sand dune bedding had been found in sandstone in Surrey but this doesn’t mean that the area experience very difference climate but actually it result from plate tectonic.
Intermediate change There have been 4 glacial age during the last thousand million years . The cooling of the earth appears to have started in the tertiary period about 20 million years BP(before present).
Short term changes Less significant change of climate have been experience after ice age. Although some change of temperature experience in post glacial period at both hemisphere but most of the report came from unreliable sources
Evidences of climate change The observation and recording of the world weather elements have only been carried out for the past 150 years. Only some area such as Europe and North America and some tropical are been observed. Remote area have a very short record.
The evidences of climate change Evidence for long term climate changes come from many sources: Pollen analysis Dendrochronology Oxygen isotope analysis Historical records, including literature and cave art Glaciological evidence Ice core research
Pollen analysis The studies of the pollen found in plant especially in peat bogs(due to water logging and lack of oxygen, decomposition is very slow) Radio carbon dating are used to determine the age of the pollen grain. Dominant species of the plant can be find by counting how many pollen of different species can be find and how many pollen of different species can be find and how the climate favour the growth of the species.
Dendrochronology Dendrochronology originate from Greek word which mean tree for Dendron and time for chronos. It is the study of tree rings and is use to date climate change for over centuries and it can monitor climate change for as far as 4000 years. Wider rings mean more growth which mean warmer or wetter conditions.
Oxygen isotope analysis It is use to study palaeoclimatology An isotope is the atom of the same element but with different atomic mass. Oxygen has two isotopes, oxygen 18 and oxygen 16.oxygen 18 is heavier than oxygen 16 therefore it does not evaporate Ice cores will be analyse to indicate amount of oxygen isotope in it. The frequency of the different type of isotopes will determine the climate.
Historical records Various evidence of the past had been gathered: Cave painting of elephant in central sahara Vines growing succesfully in england between AD1000 and AD1300 Graves for human burials in greenland which were dug to a depth of 2m in 13th century,1m in14th century and could not be dug at all in 15th century due to extension of permafrost. Fairs held on the frozen river thames in tudor times The measurement of recent advances and retreats of alpines glaciers and polar sea-ices.
Glaciological evidence The advance or retreat of glaciers is a clear response to variation in climate. Three main glacier near Chamonix in the french alps , the Mer de glace,D’argentierre and Des bossons, have been studied extensively. A rise in the temperature of only 0.5°- 1°c over 60-70 years is enough to cause glacier retreat. Eventhough some alpine glacier show slight advance since 1960s the trends are not to clear and not enough to deduce a significant climate change.
Most glacier in the northern hemisphere shows a decrease in size infact some in the European alps had decrease one third of it’s original size. This is a clear sign of an increase in temperature.
Ice core analysis A number of attempt has been done lately to to date accurately the shifts from glacials to interglacials periods by using ice cores. Microscopic s air bubbles in ice cores can also reveal information about past atmospheric pressure. The density of air suggest the height of the ice surface when the particular layer snow fell. Sensors can be used to detect chemical like carbon dioxide and nitrous oxide and micro particle changes. The quantity of acid aerosol can be use to estimate the frequency of past volcanic eruption.
Natural causes and effects of climate change. Solar activity Earth geometry and milankovitch cycles Plate tectonic Ice-albedo effect Ocean and the EL Niῆo current Volcanic activity
Solar activity Climate change is majorly caused by the change in the amount of energy emitted by the sun. Measurement from suggest that this varies rythmically It also fouund that it can be relaed to the tree ring studies.
Earth geometry and milankovitch cycles Earth geometry also varies since the sun shines to different surfaces. In 1920s Yugoslav scientist , Milutinmilankovitch had calculated three ways in which the earth’s geometry varies which is known as Milankovitch cycles.
The earth orbit around the sun changes from near-circular to being more oval on a cycle of about a millions years. The earth rolls and wobbles slightly on its axis on a cycle of 40000 years. The axis of the earth moves round slowly on a cycle of 20000 years, affecting the distance of different areas from the sun on midsummer’s day.
However the earth had exist for 250 000 years without climatic change suggest that other factor might affect it. The way the cycle define climate change had been criticised because each cycle would barely influence the amount of solar energy reaching the earth. They mainly affect seasonality as they change the distribution of energy over the earth surface .
Plate tectonic It is responsible for the moving of land into different climate. There is evidence of land masses found in the poles therefore they probably prevent warm ocean current from meeting the polar. The formation of large land masses cause the global cooling of the world
Ice-albedo effect Albedo effect is the ability of a surface to reflect solar radiation. Snow and ice has the highest albedo effect therefore it has the feedback relationship with the earth climate
Oceans and the EL Niῆo effect The oceans and seas of the world have their own circulation of warm and cold water. The undersea circulations are also closely linked with the atmospheric circulation. El Niño is related atmospheric/oceanic phenomena which disrupt the climate across much of the rest of the world from east Africa to the shores of America. El nino southern oscillations (ENSOs) occur every 2 to 9 weeks.
Volcanic eruption Volcanic eruption effect climate change since it send huge amount of particles into the air. The particle alter the original albedo effect by increasing it and thus it cause a lowering in global temperatures.
Climate change: human cause ,effect , response. Change in vegetation Pollution
Change in vegetation Variation in the spatial disribution of different plant species may be one indicator of global warming It cause deforestation which seriously disturb the balance which trigger the arise of other problem
Pollution After world war 2, the world experience a dramatic increase in temperature. This due to the increase of the usage of fossil fuel. This cause more co₂ being released and since deforestation occur around the world less tree to use the co₂ therefore it increase the chnce for global warming to occur.