Evidence For Climate Change

Glacial Deposits:- These show records of the advance during cooler periods and retreat during warmer periods

Pollen Analysis:- Species have climatic requirements that influence their geographical distributions. If pollen grains fall into an oxygen-free peat bog, they can be preserved and their location & abundance taken as representative of the vegeatation dominant at any given time. Changes in pollen can be found in different levels of the bog showing changes in climate over time

Limitation:- pollen can be transported a considerable distance

Dendrochronology:- The analysis of tree rings in core samples. You are able to see the tree's growth rate over many years. Each year the growth of the tree is shown by a ring. Warm, wet years produce large gaps between rings. Colder, drier years produce thinner bands. Vegetation preserved in non-oxygen conditions can then stretch back 10,000 years. 

Limitation:- Few trees are older than about 4000years. Trees respond more to moisture than temperature so it may be a wet, cold summer but the ring would be wide, suggesting a warm, wet summer

Ice-core analysis:- by extracting cores of ice you are able to measure the amount of C02 in the ice. In colder periods, less CO2 is trapped in air bubbles as the ice forms than in warmer years. Using this, we can date back upto 10,000years. It also enables us to compare C0s levels and the varying temepratures through history and link clearly between the two.

Sea-Floor Analysis:- Core samples of microfossils show isotope levls of oxygen -18 and oxygen-16. During colder phases, water containing the light 16-O2 evaporates more easily and once repcipitated on land, eventually becomes glacial ice. As a resutl, the oceans have a high concentration of 18-O2 while ice sheets and glaciers contain more 16O2. During warmer periods, 16O2 in the ice is released and returns to the ocean balancing the ratio. 

Isotope curves show the ratio, therefore giving a picutre of climatic change and ice volume.

Radiocarbon Dating:- Carbon-14 is a radioactive isotpe of Carbon 12. Plants take in carbon in photosynthesis. C14 decays but C12 doesn't so the abundance of 14C compared to 12C can help determin the age of the plant. Calculating the age of the plant is an indicator of climate at that period and can date organic matter upto 50,000 years old

Coleptera:- remains of coleptera beetles are common in freshwater and land sediments. Different species of this beetle tend to be found in different climate conditions. Knowledge of the present climatic range of different species, and age of sediments in which remains are found, allows part climatic conditions to be determined

Changing Sea Levels: The presence of rias and fjords indicates rising sea levels, flooding, glacial and river valleys. Changes in sea level are indicators of climatic change

Historical Records:- Since 1873 daily weather reports have been documented and the royal society encouraged the collection of data since the 1600s. Parish records are good sources fo climatic data.