GC170 1st EditionFinal Exam Study Guide Lectures: 14 - 22Final Exam May 12th 10:30 amThree parts:1. 10 multiple choice (20 points)2. 14 short answer questions a. 1-2 sentence answersb. 140 pointsc. If you attended lecture 20, 21 and 22 you can skip one3. 2 essay questionsa. 40 pointsEssay Questions: Essay Question 1: - What kind of proxy data is used to create this temperature reconstruction? o Tree-ringso Pollen records o Ice cores- How does this show the human influence on 20th century warming? o Clear warming seen in diagramo Use of proxy to show CO2 increases over the years Correlate with temperature increase- Why is it important to study paleoclimate?o Key to future: Helps to understand the pasto Historical information provides context for recent warmingo Helps predict future environmental conditionso However 20th century warming is unpredictable This level of warming hasn’t occurred beforeEssay Question 2: - What do the blue and black lines represent? o Blue line: The blue line represents model results of temperature without the influence of humanso Black line: Human Forcings on temperature- How does this show the human influence on 20th century warming? o Shows the difference between temperature with and without human forcingso Clear difference- How can Global Climate Models predict the future? (lecture 20)o Global climate models (GCM) simulate future temperatures based on CO2 emissions As well as atmosphere and energy budget Can reproduce the influence of human (fossil fuels) and natural (volcanoes, sunspots) forcings on temperature Separate out the influence of the humans (fossil fuels), GCM’s model the temperature without fossil fuel emissions- Represented by blue line- No increasing trend in the temperature without the influence of humanso GCM Simulate the components of the energy budget and atmosphere Change CO2 concentrations and surface properties = predict temperaturesTerminology: - Greenhouse effect – longwave radiation absorbed and remitted back to earth by the greenhouse gases (CO2, H2O, CH4, N2O) in the troposphere - Enhanced Greenhouse effect – increased greenhouse gases from fossil fuel emissions in the atmosphere have increased the greenhouse effect - Global Warming – an average increase in the earth’s surface temperature, related to increased fossil fuel emissions (often synonymous with climate change) - Climate – The average of many year’s worth of weather for a location/region (e.g., the annual rainfall in Tucson is 12 inches) - Climate Change – Long-term changes in the regional climate or earth’s average temperature occurring over decades to centuries (not only warming) - Climate variability – Short-term changes in the climate occurring over years to decades, usually related to natural climate forcings/influences- Weather: The state of the atmosphere at any given place or timeLecture 14:- Paleoclimate reconstructions: thousands of years are developed from proxy records (tree-rings, ice cores, pollen records)o Key to future: understanding past o Historical information provides a context for recent warmingo Help us to predict the future environmental conditions- Medieval warm periodo A period from 900 – 1300 AD- Temperature in the northern Hemisphere was warmer (~ 0.5 degrees) - Evidence from Northern Europe (Vikings in Europe settled in Greenland for 400 years)- Western USo Arid and warmer o Several long and severe droughts lasting around 20 years in the Southwesto Communities of Native Americans dispersed - Castles were built during the MWP- Little Ice Ageo Cool period from 1400 – 1800 AD- Glaciers more advanced - Holland had a lot of continuous ice- Glacial advances and more freezing temperatures- Ice Ages: changes in the earth’s orbit and the relationship between the earth and suno Large climate changes over thousands of years results in ice ages o Last ice age happened 15,000 to 20,000 years ago - Sun Spotso Output of energy from the sun slightly varies over time  Changes amount of incoming solar radiation that reaches the earth’s surfaceo More sunspots means that the sun emits more solar radiationo Fewer sunspots during little ice age- Volcanic eruptions inject large amounts of ash into atmosphere o Blocks amount of incoming solar radiation reaching the earth surface and cools the climate. Explosive volcanic eruptions emit black ash & SO2 gas,  reaches the stratosphere SO2 converts to sulfate aerosols (Fine particles that reflect incoming solar radiation) remain in the stratosphere for 1 – 2 years (stratosphere is dry &sulfate aerosols are not rained out)o Cool the global climate for 1 – 2 yearso Volcanoes near equator cool more effectively Upper-level winds transport volcanic gases and ash to cover both hemispheres Higher latitudes winds transport the ash and gases to cover a smaller area (ex: only within the northern hemisphere)Lecture 15- Ice Core Methodo In the lab  Ice is cut into sections (10 cm – 1 m)  Ice is melted  Gas bubbles are released  Water is collectedo Scientists measure:  Gas - Samples of the atmosphere reconstruct past greenhouse gas concentrationso CO2o Methane o Nitrous Oxide Water - Temperature (Hydrogen isotopes) Dust and Particulates in the ice- Dust/ash from past volcanic eruptions and pollutiono Vostok Ice Core (400,000 years) and Dome C (800,000 years) from Antarctica Shows repetitive cycles or fluctuations in CO2  Shows unprecedented CO2 levels in recent decades Such high levels have never been seen before- Tree ringso Distinct growth band that represents one year of growth Ring boundaries - Marked by the sharp transition between dark latewood cells and the early wood cells of the next ring- In the winter, the tree shuts down and stops growingo No winter in the desert o Rings not as distinct- There can be false rings so counting rings is inaccurate  Ring Width- The width of a tree ring is related to changes in temperature or precipitation- Influences (injury, climate, light/shade, nutrients) Tree Growth- Complacento Trees growing near a local water source have no variation in growth- Sensitiveo Trees on steep slopes and rocky areas represent regional changes in rainfall.o The type of growth wanted because ring width is a proxy for past climate conditions Variation between width o Cross dating: Determine how old a sample is  Trees from same region sensitive to the same environmental