GC170 1st Edition Final Exam Study Guide Lectures 14 22 th Final Exam May 12 10 30 am Three parts 1 10 multiple choice 20 points 2 14 short answer questions a 1 2 sentence answers b 140 points c If you attended lecture 20 21 and 22 you can skip one 3 2 essay questions a 40 points Essay Questions Essay Question 1 What kind of proxy data is used to create this temperature reconstruction o Tree rings o Pollen records o Ice cores How does this show the human influence on 20th century warming o Clear warming seen in diagram o 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 past o Historical information provides context for recent warming o Helps predict future environmental conditions o However 20th century warming is unpredictable This level of warming hasn t occurred before Essay 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 humans o 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 forcings o 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 o GCM 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 humans Simulate the components of the energy budget and atmosphere Change CO2 concentrations and surface properties predict temperatures Terminology 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 time Lecture 14 Paleoclimate reconstructions thousands of years are developed from proxy records treerings ice cores pollen records o Key to future understanding past o Historical information provides a context for recent warming o Help us to predict the future environmental conditions Medieval warm period o 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 US o Arid and warmer o Several long and severe droughts lasting around 20 years in the Southwest o Communities of Native Americans dispersed Castles were built during the MWP Little Ice Age o 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 sun o Large climate changes over thousands of years results in ice ages o Last ice age happened 15 000 to 20 000 years ago Sun Spots o Output of energy from the sun slightly varies over time Changes amount of incoming solar radiation that reaches the earth s surface o More sunspots means that the sun emits more solar radiation o 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 years o 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 Method o In the lab Ice is cut into sections 10 cm 1 m Ice is melted Gas bubbles are released Water is collected o Scientists measure Gas Samples of the atmosphere reconstruct past greenhouse gas concentrations o CO2 o Methane o Nitrous Oxide Water Temperature Hydrogen isotopes Dust and Particulates in the ice Dust ash from past volcanic eruptions and pollution 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 rings o 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 growing o No winter in the desert o Rings not as distinct o o o o o 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 Complacent o Trees growing near a local water source have no variation in growth Sensitive o 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 variable can be matched with other trees Dendrochronology Dating and study of annual rings in trees Dendros growth of tree rings Chronos time ology the study of Chronology a record of events Four criteria for suitable tree ring sampling Has rings Clear Ring boundaries