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evidence and causes of Climate change (The Earth is getting warmer…
evidence and causes of Climate change
The Earth is getting warmer
climate change = a significant change in the earths climate over a long period of time
the climate constantly changes always has always will
Quaternary period is the most recent geological time period
Quaternary period = 2.6 million years ago to today
before Quaternary climate was warmer and quite stable
Quaternary global temp. shifts between cold glacial periods that lasts 100 000 years to warmer interglacial periods that last around 10 000 years
The last glacial period ended around 15 000 years ago since then the climate has been getting warmer
global warming is the term used to describe the sharp rise in temperature over the last century
evidence
ice and sediment cores
ice sheets are made up of layers of ice
one layer forms each year
scientist drill into ice sheets to get long cores of ice
analysing trapped gasses means they can see what temp. it was that year
Tree rings
each year trees grow a new ring
warmer, wetter conditions = thicker rings
scientist take cores and count the age of the tree and the conditions each year
source of evidence for the past 10 000
pollen analysis
pollen gets preserved in sediment
scientists can identify the date of pollen to show what species were around at the tie
scientists know conditions of pollen now so preserved pollen from similar plants show that the conditions were similar
Temperature Records
since 1850 global temp. have been measured using thermometers.
reliable but short term records of temp. change
historical records weather reports and harvest dates extend further back
causes
natural
orbital changes
the way the earth moves round the sun changes
goes from perfect circle to an ellipse (oval) every 96 000 years
effect the amount of solar radiation
more energy the earth gets from the sun the hotter it gets
orbital changes may have cause the glacial and interglacial cycles
volcanic activity
large volcanoes eject large amounts of material into the atmosphere
particles intercept the suns rays cooling the surface of the earth
volcanoes also release carbon dioxide but not enough to cause warming
volcanic activity may cause short term changes in the climate eg. the cooling that followed 1991 mount Pinatubo
solar output
the suns output energy isn't constant
it varies in short 11 year cycles and also longer several 100 year cycles
when solar outputs reduce the temperature in some areas is cooler
most scientist dont think that solar output changes are a major cause of climate change
human
cement production
when produced cement produces lots of carbon dioxide as it is made of limestone
deforestation
plants absorb carbon dioxide for photosynthesis
when plants or trees are cut down they stop taking in carbon dioxide
carbon dioxide is also released when plants and trees are burnt to make way for agriculture or fuel
farming
livestock produce lots of methane
rice paddies contribute as flooded fields emit methane
burning fossil fuels
when fossil fuels are burnt they release carbon dioxide