Teacher Resource 1
Task 1: Climate change proxy analysis
Parameter / Image / Proxy Analysis / What does this indicate about Earth’s past climates?Tree rings / / Tree growth is influenced by temperature and rainfall i.e. the climatic conditions. Patterns are analysed in tree-ring widths, density, and isotopic composition that all give indications of the climate at that time. In the UK and other temperate areas trees will produce a new ring every spring and these provide a record of the climatic conditions. Some trees can survive for thousands of years and so will preserve valuable archives of climate data that are extracted from tree cores, similar cores are drilled into ice. / Thick wide rings indicate periods of fertility when precipitation is high and narrow rings indicate drier periods. Evidence needs to be handled with care as tree rings can be affected by other variables e.g. soil, pollution and wind.
Ice cores / / Ice has accumulated from snowfall over many centuries and millennia having formed solid ice packs. It is possible to drill through the ice to collect ice cores which contain dust, air bubbles, or isotopes of oxygen that can be used to interpret the past climate of that area. / CO2was stable over the last millennium until the early 19th century. However its concentration is now nearly 40% higher than it was before the industrial revolution. CH4 has doubled since pre-industrial levels.
Version 11© OCR 2017
Climate Change
Parameter / Image / Proxy Analysis / What does this indicate about Earth’s past climates?Marine and lake sediments / / Billions of tonnes of sediments accumulate in the world’s oceans, lakes, and rivers every year and the deeper the sediment the older it is e.g. the surface sediments reflect the climatic conditions in the present day. Sediment cores are collected and materials examined to determine historic marine conditions e.g. ocean temperatures. / The ratio of oxygen isotopes 16 and 18 can be analysed to determine historic ocean temperatures. Sediments rich in heavy oxygen (oxygen-18) indicate cold temperatures and match with past ice ages.
Fossils / / The remains of plants and animals can get buried in sediments and can be identified thousands of years later. Species require specific climatic conditions and hence scientists can deduce what the climate what like at the time the remains were deposited. Radiocarbon dating is used to determine the age of the fossils. / A range of species have been identified globally, including many along the UK’s Jurassic coastline, such as Ammonites that indicate that temperatures were once warmer in the past.
Parameter / Image / Proxy Analysis / What does this indicate about Earth’s past climates?
Fossil pollen / / Each species of plant produces pollen grains that have a distinct and identifiable shape. These pollen grains are well preserved in the sediment layers that form in the bottom of a lake or ocean. By analysing the pollen grains in each layer, the type of plants were growing at the time the sediment was deposited can be determined. Conclusions can then be made about the climate at the time when those pollen grains were deposited. / The amount of pollen deposited in a given time period indicates the abundance of vegetation, high concentrations indicating warmer periods. Species found in savannah ecosystems have been identified in the Amazon basin indicating drier conditions in the past.
Corals / / Calcium carbonate forms the skeleton of corals and this is extracted from sea water. This hard skeleton thus contains oxygen and the ratio of isotopes of oxygen can be used to determine the temperature of the water in which the coral grew. / Higher concentrations of heavy isotopes indicate warmer ocean temperatures and lighter cooler temperatures- this has coincided with records of temperatures in the Atlantic ocean.
Version 11© OCR 2017
Climate Change