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UW ATMS 587 - Study Notes

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DARGAN M. W. FRIERSON DEPARTMENT OF ATMOSPHERIC SCIENCES DAY 8: 10/21/2013 Climate Dynamics (PCC 587): Climate RecordsThe Instrumental Record from NASA ! Global temperature since 1880 13 warmest years: 2001-2012 and 1998 (biggest El Niño ever)Separation into Northern/Southern Hemispheres ! N. Hem. has warmed more (1o C vs 0.8o C globally) ! S. Hem. has warmed more steadily though Cooling from 1940-1975 only in the N. Hem. (likely due in part to “global dimming” from aerosols)Spatial Structure of the Warming ! NASA temperature record, 5 yr averagesThermometers ! Temperature is easy to measure ! Some history: ¡ Ancient Greeks knew that gases/liquids expand when heated ¡ Galileo played around with thermometer-type devices (1592) ¡ Ferdinand II de Medici, Grand Duke of Tuscany, invented sealed glass thermometer (much more accurate) around 1650 ÷ Measured temperatures within artificial incubators to hatch chicks ÷ Established the first international network of weather stations ¢ 7 stations in Italy, also Warsaw, Paris, Innsbruck, OsnabruckTemperature Scales ! Daniel Gabriel Fahrenheit invented his scale in 1724 ¡ Also invented the mercury thermometer (1714) ¡ Scale based on three points: ÷ Freezing point (32o) ÷ Cold temperature of an ice/salt/water mixture (0o) ÷ Underarm body temperature (96o) ¡ Later redefined slightly to just depend on 32o and 212o… ! Anders Celsius (1742) ¡ Based on 0o for boiling and 100o for freezing! ¡ Switched by Linnaeus in 1745Central England temperature record (since 1659!)Weather Observations ! Meteorological Society of Mannheim (1780): ¡ 37 stations in Europe, 2 in North America ¡ Very rigorous procedures for making measurements, calibrating instruments ! Invention of telegraph allowed for quick construction of weather maps by 1850 ! First International Meteorological Conference (August 1853) ¡ US Navy Lieutenant Matthew Fontaine Maury developed standard procedure for meteorological observations on shipsSurface temperature measurement protocol Thermometer between 1.25-2 m (4-6.5 ft) above ground White colored to reflect away direct sunlight Slats to ensure fresh air circulation “Stevenson screen”: invented by Robert Louis Stevenson’s dad ThomasThermometer Measurements ! Bank thermometers make me LOL ¡ Often poorly sited, read highTemperatures over Land Only ! NASA keeps track of land-only measurements separately Warming in the station data record is larger than in the full record (1.1o C as opposed to 0.8o C)Sea surface temperature measurements “Bucket” temperature: older style subject to some cooling by evaporation Starting around WWII, many measurements taken from condenser intake pipe instead of from buckets Standard bucket Canvas bucket Insulated bucket (~1891) (pre WWII) (now)1850 WW I WW II Percent coverage of ocean by year 1900 1990 19501981-1997 1901-1920 10% = 1 in 10 months had a ship measurement Percent coverage of oceanConstructing the Global Temperature Record ! Groups construct global temperature based on data that follows these procedures ! Decent enough global coverage started around 1880-1890Other estimates (UEA)Climate Data Groups ! National Climatic Data Center (NOAA) ¡ Asheville, NCClimate Data Groups ! University of East Anglia Climate Research Unit (CRU) ¡ Norwich, England ! Hadley Centre ¡ Exeter, EnglandClimate Data Groups ! Goddard Institute for Space Studies (NASA) ¡ New York, NYRaw Weather Station DataConstructing Global Temperature ! Groups like NASA, NOAA, CRU have two steps: ¡ Remove inhomogeneities in individual stations due to changes in observing practices, station environment, or other non-meteorological factors ÷ E.g., urban stations are removed ¡ They also have well-documented procedures for combining fragmented record. You can download raw weather station data from the “World Monthly Surface Station Climatology” http://rda.ucar.edu/datasets/ds570.0Temperature anomaly (oC) UW researchers Kevin Wood & Eric Steig took random sets of 32 stations and compared the raw data to the CRU analysis. CRU weeded out some extremes but didn’t change the average much One sample station Histogram of trends from 32 stations Step 1Constructing Global Temperature ! Centers have different procedures for filling in gaps where there’s no data ! Notice how there is differences among centers recently? ¡ Let’s discuss why…Constructing Global Temperature ! CRU and NOAA don’t include the Arctic Ocean where there’s no data ! NASA fills these points with the nearest station ! So CRU and NOAA are not including one of the locations that’s clearly warming the fastest! ¡ But that’s their procedure & they’re sticking to it… NASA CRUPitfalls of temperature measurements incomplete spatial sampling short and “gappy” records instrument changes changes in station site, sometimes undocumented changes in exposure of station site changes in observing protocol transcription errors invalid data (faulty instruments, unreliable observers) “urban heat island” effectVirtue of the temperature measurements: Redundancy Many different stations Three different data sets (land, ocean, upper air) Multiple analysis methods by different groups Random errors tend to average out Systematic errors can be removed by calibration Estimated uncertainty with global temperature measurements: currently 0.1o C (and more in the past).1950 2000 1900 1850 Is this feature real? The accidental discovery that it isn’t? Case study 1Former UW grad student (with Wallace)? Agung El Chichon Pinatubo Santa Maria? 1945: Could it be the effect of the atomic bombs?Sea surface temperature: Now you see it!Sea surface temperature: Now you see it! Land surface air temperature: Now you don’t!Reason for Discontinuity ! US ships mostly used engine room intake measurements ¡ These are biased slightly warm ! UK ships mostly used uninsulated bucket measurements ¡ These are biased slightly cold ! Switch from mostly US ships during the war to a lot more UK ships after the war led to the false drop in temperature ¡ Groups are working on


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