CC 1.1

• What is the study of the past climate called - Palaeoclimatology
• Why do we need to use climate proxies - Because meterological data cannot be used to go back more than hundreds of years
• What are climate proxies - Preserved natural characterisitics of the past which act as natural recorders of climate variability
• Name all of the methods of reconstructing the earths past climate (5) - Sea floor sediments - Ice cores - Lake Sediments - Dendrochronology - Fossils
• How far back can sea floor sediments be used for 170 million years back
• Describe how sea floor sediments can be used to reconstruct past climates (2) - Fossil shells of sea creatures called fominifera accumulate in sea floor sediments - The shells contain calcium carbonate, with its chemical composition telling us the sea level and temperature of the time as different species of fominifera thrive in different water temperatures
• What does the abundance of fominifera in sea floor sediment tell us - what the conditions were like at the time as species thrive in different temperatures
• What are the advantages of using sea floor sediments to reconstruct past climates - Ocean is undisturbed from weathering - Complete image of 170 million years (a long coverage)
• what is the range of using ice core data to reconstruct past climates - 2.7 million years
• How can ice core analysis be used to reconstruct past climates - Ice core contain bubbles of air trapped in formation of the ice - Bubbles provide a record of gaseous conditions of the atmosphere with the relative frequencey of oxygen and hydrogen atoms with stable isotopes can be measured
• What does the concentration of 16O and 18O atoms in ice core analysis tell us about the climate - 16o evaporates more easily, so if there is lots of 16o then the climate was cooler, but if there was more 18o then the climate was hotter as it takes longer to evaporate
• What are the advantages of using ice core data - Great data - Easy to date ice as it is visually structurally different between winter/summer and cooler/warmer periods
• Disadvantages of using ice core analysis to recontruct past climates - Only covers quaternary period (2.7 million years)
• What do lake sediments contain - Pollen grains - Diatoms - Varves
• What is the range of pollen grain analysis in lake sediments - 240 million years
• How can lake sediments in the form of pollen grain be used to reconstruct earths past climate (2) - pollen analysis shows past vegetation types inferring past climatic conditions - IE at the end of the last ice age pollen analysis shows boreal forest in the UK
• How can lake sediments in the form of diatoms be used to reconstruct earths past climate (2) - Microscopic plants preserved in lake sediments which are sensitive to different conditions - Made from silica which helps them preserve well
• How can lake sediments in the form of varves be used to reconstruct earths past climate (3) - Tiny layers of lake sediment made from light and dark bands - Light bands are formed from coarser sediments from spring and summer (high energy melt-water runoff) - Dark bands are from fine sediment showing deposition in the winter months when lake surfaces are frozen
• Advantages of using lake sediments in all forms to reconstruct earths past climate - Dates all the way back into mid-cretaceous era (240 million years)
• How long ago can dendrochronology be used to reconstruct earths past climate 13,500 years
• How can dendrochronology be used to reconstruct past climates (2) - Tree rings (annules) mark a year in the trees life and respresent a cycle of the seasons growth - Annules vary in width depending on temperature and moisture availibility (as it grows quicker)
• What are the disadvantages of using dendrochronology to date past climates - Trees are not very old and do not live for long, hence is not very useful (most trees are no older than 5000 years)
• How many years can fossils reconstruct earths past climate 600 million years - bacteria fossils can date back 3.5 billion years
• How can fossils be used to reconstruct earth's past climate (2) - Plants and animals require specific environmental conditions, with some sensitive to temperature and moisture fluctuations - where these specific species can be found in fossil records, they can be used as climate proxies
• What are the advantages of using fossils to reconstruct past climates - Some fossils are really common (ammonities) and date back 150 million years, hence cover a long timespan
• What are the 3 variables of natural forcing - Plate tectonics and volcanic activity - Milankovitch cycles - Solar output
• How do volcanic eruptions influence long term climate (2) - Volcanic ash and sulphur dioxide pumped into stratosphere, volcanic ash quickly removed - But sulphur dioxide becomes sulphuric acid whihc fomrs sulphate aerosolds reflecting radiation back into space lowering temps
• Describe the effect on Mount Pinatubo eruption in June 1991 on climate - Injected 20 million tonnes of sulphur dioxide into atmosphere and over 3 years cooled the earths climate by 1.3 degrees
• Describe the effects of Tambora's eruption in 1815 (2) - Cooled land temperatures in 1816 by 1.9 degrees - European summer of 1816 was described as the year without summer
• How does the movement of continents (plate tectonics) influence long term climate - Affecting the balance of radiation incoming and outgoing - ei where large continents occupy higher altitudes there will be more permanent snow and ice resulting in albedo effect and positive feedback
• How does ocean circulation (plate tectonics) influence long term climate (2) - Isthimus of north and south america intensified gulf stream increasing precipitation, with the prevailing winds blowing precipitation into atlantic - As a result the water surface was less saline and reduction in heat transferred by thermo haline circulation allowing sea ice to build up
• Describe orbital eccentricity (2) - Varying elliptical orbital path of the earth over 100,000 - At the maximum eccentricity there is a 30% difference in solar radiation between the closest and furthest point from the sun
• What is the impact of orbital eccentricity (milankovitch cycle) on long term climate (2) - Changes the distance short wave radiation must travel to get to earth - An ice age may occur at maximum eccentricity as less of the suns energy accesses the earth
• Describe obliquity - Tilt of the earths axis over 40,000 years from 22 degrees to 24.5 degrees
• What is the influence of obliquity (milankovitch cycle) on long term climate - When the tilt is closer to 22 degrees it increases the difference in radiation between polar and equatorial areas, hence snow and ice accumulated in winter may not melt in summer increasing positive feedback as albedo is increased
• Describe precession (milankovitch cycle) and its impact on long term climate (2) - Earth 'wobble' on its axis with periodicity of 22,000 years - Fairly insignificant on climate
• What is solar output in relation to affecting long term climate (2) - Sunspot activity correlates with solar energy output - Solar output tends to follow an 11 year cycle
• Describe the correlation between solar radiation and volcanic activity with respect to long term climate (2) - When solar radiation has decreased, volcanic activity has increased - As a result global temperatures suddenly plummet within months
• Describe previous impacts on the climate as a result of solar output (2) - Near the end of the 1600's sunspot activity was near 0, coinciding with severe winters in europe, known as the little ice age - In recent years sunspot activity has been high coniciding with warming climate
• How long ago was the quaternary period, and how long ago was the holocene period - 1.64 million years ago to present (quaternary) - 10,000 years ago to present (holocene)