// lecture 02 Flashcards
15 of the warmest years occurred in the last
17 yrs.
a running means averages
N things together, then steps forward on unit and repeats.
northern hemisphere has warmed
more (1 C vs 0.8 C globally).
southern hemisphere has warmed
more steadily though.
cooling from
1940-1975 only in the northern hemisphere.
thermometers
ancient Greeks knew that gases/liquids expand when heated.
Galileo
played around with thermometer type devices (1592).
Ferdinand II de Medici
invented the sealed glass thermometer (more accurate) around 1650. measured temps. within artificial incubators to hatch chicks. established the first international network of weather stations, with 8 stations in Italy, also Warsaw, Paris, Innsbruck, Osnabruck.
Daniel Gabriel Fahrenheit
invented his scale in 1724. also invented the mercury thermometer (1714). scaled based on three points: freezing points (32), cold temp. of an ice/salt/water mixture (0), and underarm temp. (96). later defined to just depend on 32 and 212 degrees.
Anders Celsius
1742; based on 0 for boiling and 100 for freezing. reversed to make 0 freezing and 100 boiling by Linnaeus in 1745.
Meteorological Society of Mannheim
37 stations in Europe, 2 in North America. very rigorous procedures for making measurements, calibrating instruments.
invention of the telegraph allowed for
quick construction of weather maps by 1850.
first international meteorological conference (august 1853)
US navy lieutenant Matthew Maury developed standard procedure for meteorological observations on ships.
Stevenson screen
invented by Robert Stevenson’s dad Thomas (1818-1887). thermometer between 1.25-2 m above ground. white colored to reflect away direct sunlight. slats to ensure fresh air circulation. needs water supply for wet bulb temp. difference between wet and dry gives humidity.
NASA keeps track of land-only measurements
separately. warming in the land station data record is larger than in the full record (1.5 C vs 1 C).
“bucket” temperature
older style subject to some cooling by evaporation.
starting around WWII, many measurements taken from
condenser intake pipe instead of from buckets.
good enough global coverage started around
1880-1890.
groups like NASA, NOAA, CRU, have two steps:
1) remove inhomogeneities in individual stations due to changes in observing practices, station environment, or other non-meteorological factors.
2) they also have procedures for combining fragmented record. well documented.
missing data
CRU and NOAA don’t include the arctice ocean where there’s no data. NASA fills these points with the nearest station. others, excluding NASA, aren’t including the rapidly warming area.
pitfalls of temperature measurements:
incomplete spatial sampling; short and “gappy” records; instrument changes; changes in station site, which is sometimes undocumented; changes in exposure of station site; changes in observing protocol; transcription errors; invalid data (faulty instruments, unreliable observers); and “urban heat” island effect.
virtue of the temperature measurements:
redundancy, many different stations, three different data sets (land, ocean, upper air), and multiple analysis methods by different groups.
- random errors tend to average out.
- systematic errors can be removed by calibration.
- estimated uncertainty with global temp. measurements: currently 0.1 C.
Berkeley Earth Surface Temperature (BEST) group
started by Richard Muller. had funding from various sources, including the Koch brothers. found 3 things.
BEST discovery #1
found that the urban heat island effect is locally large, but does not contribute significantly to the average local temp.
BEST discovery #2
about 1/3 of temp. sites reported cooling over the past 70 years. 2/3 of the sites show warming.
BEST discovery #3
the El Nino-Southern Oscillation (ENSO) is generally thought to be the main reason for inter-annual warming or cooling, but they found that the global temp. correlate more closely with the state of the Atlantic Multidecadal Oscillation (AMO) index; which is a measure of sea surface temp. in the North Atlantic.
how to define an AMO by:
taking the SST over the N. Atlantic, remove the linear trend or some other smooth variation. the leftover is the AMO. high in 1940 and 2000, low in 1970-1990.
remote temperature sensing
the microwave sounding unit (MSU) since 1979. works like infrared thermometer, except microwave. multiple wavelength channels give temperatures at different heights. global coverage twice daily.
radiosondes
weather balloons; since 1946.
In 2001…
we thought that the surface warmed much faster than the upper atmosphere. yet, both are supposed to heat up together.
prior to 2001…
global warming skeptics, Spencer and Christy, and the UAH team were the sold producers of the MSU satellite estimates.
Remote sensing systems (RSS)
also now produce a satellite temperature record. offers independent estimates of trends and shows much significant warming. Celeste Johanson identified an error in the algorithm. Show substantial upper air warming.
More than ____ of scientists are convinced that ______
97%; the global is warming.
