Transcript File
Long term evidence for climate change 1. Ice Cores Explanation... • Best evidence for climate change comes from Greenland and Antarctic ice cores • Ice cores are a frozen record of past climates... Like a time capsule • Within these layers the ice contains air bubbles which contain carbon dioxide and oxygen isotopes. • From looking at the graph you can see clearly the periods of low concentrations of CO2 occur during glacial periods • High concentrations of CO2 link with warmer periods of time- like the Holocene interglacial we are going through now • Low CO2 = Low sea level Long Term 1. Ice Cores Long Term • From looking at the graph below you can see clearly the periods of low concentrations of CO2 occur during glacial periods • High concentrations of CO2 link with warmer periods of time- like the Holocene interglacial (in between glacial times) we are going through now. • Low CO2 = Low sea level Long Term 1. Ice Cores- How accurate and reliable are these sources of data? • The sequences of sea level change links very closely with oxygen and CO2 isotope levels suggesting that this is a very reliable source! 2. Pollen Analysis Long Term • Pollen is produced by all plants and was extracted from sediment cores in peat bogs and lake beds. • Pollen grains are preserved in waterlogged sediments. • By analysing Pollen we can see how ecosystems have changed in response to climate change. 2. Pollen Analysis- How accurate and reliable are these sources of data? Long Term • Not as reliable - as accurate pollen reconstructions rely on good preservation of pollen. Long pollen sequences are rare, and vegetation change may lag behind “climate change”. Where do we get the medium term evidence for climate change from? 1. Tree Rings (Dendrochronology) • Many trees are sensitive to changes in temp, sunlight and precipitation • In warm years trees have wide rings & vice versa • Record can go back 10,000years+ Medium Term 1. Tree rings- How accurate and reliable are these sources of data? • Good reliability – However, tree records only give localised records. Medium Term 2. Paintings and written accounts Bruegel Painting 1565 London Frost Fair 1789 Medium Term Dickensian Winters • Written word is also good evidence; they provide description of climatic conditions Medium Term 2. Historical records- How accurate and reliable are these sources of data? • Unreliable – These sources did not set out to record climate, and must be used with care. They are usually local, and difficult to generalise. 3. Glacier Retreat Medium Term 3. Retreating glaciers Medium Term • Glaciers change in response to climate change. • We can look at old photos/maps/paintings to measure direct differences in glacial positions Medium Term 3. Retreating Glaciers- How accurate and reliable are these sources of data? • Reliable – Good records stretch back to around 1880, before this the record is patchy. Where do we get the short term evidence for climate change from? • The last 128yrs of data suggest the Earth is 0.7 – 0.8 oC warmer • 11 of the world’s hottest 12 years occurred in the decade 1995-2006 • Global warming or natural change? Short Term • Link between CO2 & temperature • Is the increase in CO2 anthropogenic (human) or natural changes? ...Most scientists agree anthropogenic Short Term • 3 possible effects of climate change!