MET 112 Global Climate Change – Lecture 7What does ‘to observe’ mean?Slide 3Slide 4Slide 5Ice Core layersIce CoresSlide 8Slide 9Time Series Analysis: Examples of Temperature ChangeExamples of Temperature ChangeTrendThis graphs representsSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Time Frames -- ExamplesSlide 22Slide 23Latest global temperaturesTemperature over the last 10 yearsSlide 26Slide 27What Changed Around 1800?Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Instrumental Air Temperature RecordSlide 46Slide 47Slide 48Burning of Fossil FuelsLand-Use ChangesSlide 51Slide 52Greenhouse GasesMethaneAnthropogenic Methane SourcesNitrous Oxide N2OAnthropogenic Sources of Nitrous OxideCFCs (Chlorofluorocarbons)Sources of CFCsThe Land and Oceans have both warmedPrecipitation patterns have changedMET 112 Global Climate Change – Lecture 7Observations ofObservations ofRecent Climate ChangeRecent Climate ChangeDr. Craig ClementsDr. Craig ClementsSan Jose State UniversitySan Jose State UniversityOutlineHow do we observe?Recent trends in temperatureRecent trends in GHGsWhat does ‘to observe’ mean? Measurements–Of what? Who compiles these measurements for governments and society?IPCC: Intergovernmental Panel on Climate Changewww.ipcc.chWhere do our observations come from? - to watch and record.Temperature stationsChange in surface temperature in 20th centuryBubbles Trapped in ice corePetit, Jean-Robert, et al (1999). “Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica”. Nature 399: 429-436.Ice Core layers •GISP2 ice core (Greenland Summit)•Archived at the National Ice Core Laboratory in CO.•from 1837-1838 meters in which annual layers are clearly visible. •The appearance of layers results from differences in the size of snow crystals deposited in winter versus summer •Counting such layers has been used (in combination with other techniques) to reliably determine the age of the ice. •This ice was formed ~16250 years ago during the final stages of the last ice age and approximately 38 years are represented here.Ice CoresCoring Earth’s ice sheetsCoring mountain glaciersTime Series Analysis: Examples of Temperature ChangeTrendsPeriodic OscillationsRandom VariationsJumpsExamples of Temperature ChangeDraw the following:1. Trend2. Oscillation3. Trend + Oscillation4. Random variations5. Random + trend6. Jump7. Random + jumpTrend100806040200TimeTemperatureThis graphs represents1. Trend2. Oscillation3. Trend+Oscillation4. Random variation5. Random+Trend6. Jump7. Random+Jump100806040200TimeTemperatureThis graphs represents1. Trend2. Oscillation3. Trend+Oscillation4. Random variation5. Random+Trend6. Jump7. Random+Jump100806040200TimeTemperatureThis graphs represents1. Trend2. Oscillation3. Trend+Oscillation4. Random variation5. Random+Trend6. Jump7. Random+Jump100806040200TimeTemperatureThis graphs represents1. Trend2. Oscillation3. Trend+Oscillation4. Random variation5. Random+Trend6. Jump7. Random+Jump100806040200TimeTemperatureThis graphs represents1. Trend2. Oscillation3. Trend+Oscillation4. Random variation5. Random+Trend6. Jump7. Random+Jump100806040200TimeTemperatureThis graphs represents1. Trend2. Oscillation3. Trend+Oscillation4. Random variation5. Random+Trend6. Jump7. Random+Jump100806040200TimeTemperatureTime series of climate dataTime series of climate dataTime Frames -- ExamplesSeconds to minutes – Small-Scale TurbulenceHours – Diurnal Cycle (Caused by Earth’s Rotation)Hours to Days – Weather SystemsMonths – Seasonal Cycle (Caused by tilt of axis)Years – El Niño Decades -- Pacific Decadal OscillationCenturies – Warming during 20th Century (Increase in greenhouse gases?)Tens of thousands of Years – Irregularities in Earth’s motionsMillions of Years – Geologic ProcessesClimate ChangeClimate “Variability”Time Series Data: High Frequency (10 Hz = 10 samples/sec)Latest global temperaturesTemperature over the last 10 years…“Over the last 140 years, the best estimate is that the global average surface temperature has increased by 0.7 ± 0.2°C” (IPCC 2007)So the temperature trend is: 0.7°C ± 0.2°CWhat does this mean?Temperature trend is between 0.8°C and 0.4°CThe Uncertainty (± 0.2°C ) is critical component to the observed trendCurrent CO2: ~383 ppmWhat Changed Around 1800?Industrial Revolution–Increased burning of fossil fuels Also, extensive changes in land use began–the clearing and removal of forestsIce core recordIncrease in ocean temperature causes a decrease in the solubility of CO2 in sea water (outgassing), which increases the atmospheric loading of CO2 (Stott et al. 2007). In the Vostok Ice core, carbon dioxide concentrations lagged behind the temperature by about 600±400 years (Caillon et al. 1999). What caused the large temperature changes?Three cycles of the Earth’s orbit: called Milankovitch cyclesMilankovitch cycles: EccentricityEarth’s orbit around the Sun (Earth-Sun Distance)The closest point to the Sun in a planet's orbit is called perihelion. The furthest point is called aphelion.1. Eccentricity: “off-centerdness” of the orbit varies over time in a complicated way. • Net result: two main cycles– one averages ~100,000 years and another about 400,000 years. • When eccentricity is low there is little change through the year in the Earth-Sun distance. • When eccentricity is high-the sunlight reaching Earth is ~20% stronger at perihelion than at aphelion.Earth’s orbit around the SunEccentricityoff-centerdness” of the orbitEarth’s tilt: ranges from ~21.8º to 24.4º and changes over the course of ~41,000 yearsWhen the tilt is most pronounced, it allows for stronger summer Sun and weaker winter Sun– especially at high latitudes. Ice ages often set in as the tilt decreases:Because the progressively cooler summers can’t melt the past winter’s snow. At the other extreme, it can bring the Earth out of an ice age.Milankovitch cycles: Obliquity of the Earth’s AxisPrecession: Angular motion (wobble) of the Earth’s axis of rotation. - varies ~26,000 years. Milankovitch cycles: Precession of Earth’s Axis of Rotation.0ºearthPrecessionObliquityIce core CO2 recordRetreat of mountain glaciers: ‘visual