Learning Objectives Know how scientists have got data from the past to create graphs of climate change Understand that we can look at Climate change as both long and short term events Will be able to evaluate how reliable past records are to use

Is climate change natural or human induced? The problem with global warming is that everyone agrees that it is happening, but there is fierce debate about how and why? Many Scientists believe that climate change is a result of the enhanced greenhouse effect

The combined effect of increase in greenhouse gases!

So what are the greenhouse gases? The 4 main greenhouse gases are: CO2 Methane CFCs Nitrous Oxide But many scientists do not think it is purely this!

Climate Change is not a new thing! The worlds climate has been changing over the last 18 000 years, sometimes getting hotter and sometimes colder as you can see from the graph below. We will look next lesson at some reasons why scientists think Global warming is a natural event!

Where do we get the long term evidence for climate change from? 1. Ice Cores 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.

1. Ice Cores 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 we are going through now!

1. Ice Cores From the ice cores we can also detect oxygen isotopes. Combined with the CO2 isotopes the 2 link in well to explain sea level changes. When there was low levels of CO2 recorded sea levels were lower (think why???)

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 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? 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+

1. Tree rings- How accurate and reliable are these sources of data? Good reliability – However, tree records only give localised records!

2. Paintings and written accounts 6b. Paintings are a good line of evidence Bruegel Painting 1565 London Frost Fair 1789

Dickensian Winters 6c. The written word is also good evidence

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

3. Retreating glaciers Glaciers change in response to climate change. We can look at old photos/maps/paintings to measure direct differences in glacial positions

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?

Short Term Link between CO2 & temperature Is the Carbon Anthropogenic (human) or Natural? Most scientists agree Anthropogenic

Short Term 3 possible effects of climate change!

To end… Give 2 examples of research methods that show long term historical climate change? How reliable are these? Give 2 ways of measuring medium term climate change? What about short term?