Evidence For Climate Change Flashcards
Define climate change
Evidence shows that change has always been a feature of the Earth’s climate. Apart from the Pleistocene ice age, recent research has revealed a series of climatic trends on a variety of timescales
Define global warming
The recent gradual warming of the Earth’s atmosphere largely as a result of human activity
Since when has the climate in Britain been increasing
Since the end of the Pleistocene, however the climate change fluctuates
When did the Thames freeze over
Frequently within the 16th to 19th century
What is most of the evidence for climate change
Indirect - climatic changes are inferred from changes in indicators that reflect climate, such as vegetation
Pollen analysis
Species have climatic requirements that influence their geographical distributions. Each species has different shaped pollen grains- if these fall into peat bogs they resist decay.
Limitation of pollen analysis
Pollen can be transported considerable distances by wind or sometimes wildlife
Dendrochronology
Tree rings from core samples
1 band in spring, 1 in autumn
Wide band = warm and wet year
Narrow band = cooler and drier year
Limitations of dendrochronology
Recent investigations - trees respond more to levels of moisture than to temperature
Few trees are older than 4,000 years
How can dendrochronology be used to go back further than 4,000 years
Using remains of vegetation preserved in non-oxygen conditions
Ice-core analysis
Drilling cited from areas such as Antarctica and Greenland.
Use the CO2 as a climatic indicator- low CO2 during cooler periods and higher when uts warmer
Another method of examining ice-core analysis
Oxygen isotope levels
Sea-floor analysis
Core samples from the ocean floor reveal shifts in animal and plant populations, which indicate climatic change.
Sea-floor analysis results
Isotopes-
When water evaporated from the oceans and precipitated onto the land eventually forms glacial ice, water containing lighter oxygen-16 is more easily evaporated than that containing heavier oxygen-18. Oceans higher in oxygen-18 while glaciers higher in oxygen-16. During warmer periods oxygen-16 in ice is released and red turns to the oceans, balancing out the ratio.
Recent investigations of sea floor analysis
Suggests that isotope variations show changes in the volume of ice rather than water temperature, but as ice volume itself reflects climatic conditions, such studies have tended to confirm earlier findings.
