17 January 2011 How and Why Does Climate Change Climate changes over a broad range of time scales Years decades centuries millennia Many factors combine to affect climate Variability of incoming solar radiation ID: 698294
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Slide1
Climate and Climate Change
17 January 2011Slide2
How and Why Does Climate Change?
Climate changes over a broad range of time scales
Years, decades, centuries, millennia
Many factors combine to affect climate
Variability of incoming solar radiation
Regular changes in Earth’s orbit
Volcanic eruptions
Changes in Earth’s surface characteristics
Human activitiesSlide3
Climate Definition
Weather of a locality averaged over a time period30 year periods, beginning with start of a decade
Current period is
1971-2000
Plus extremes in weather
Temperature, precipitation, air pressure
Wind speed, cloudiness (may use entire station record)
http://www.ncdc.noaa.gov/oa/ncdc.htmlSlide4
Climatic Anomalies
Departure from long-term climatic average of the average for a particular week, month, or yearPrecipitation anomalies are more complex than temperature anomalies
Variability of storm tracks
Almost random distribution of convective showers
Mid- and high latitudes affected by westerly wave patternsSlide5
Temperature Anomalies – US, Dec 2007Slide6
Precipitation Anomalies – US, Dec 2007Slide7
Climate Boundary Conditions
Climate determine by conservation of energy and conservation of massClimates of specific localities shaped by boundary conditions, e.g.,
Latitude, elevation, topography
Proximity to large bodies of water
Earth’s surface characteristics
Atmospheric and oceanic circulation
Boundary conditions of first 4 change over 10
6
-10
8
yearsSlide8
January Mean Sea-level Air Temperature (C)
Fig. 15.3, p. 455Slide9
July Mean Sea-level Air Temperature (
C)
Fig. 15.4, p. 456Slide10
Mean Annual Precipitation (mm
)
Fig. 15.5, p. 458Slide11
Köppen
Climate Classifications
Letters h, k and a, b, c, d indicate relative warmth, coolness
See Appendix III, p. 509-515
Table, p. 510Slide12
Earth’s Climate Record
Based onHistorical documentsFossil plants and animals
Pollen profiles
Tree growth rings
Glacial ice cores
Deep sea sediment coresSlide13
Geologic Time Scale
Plate tectonics complicates climate reconstruction
Fig. 15.6, p. 460Slide14
Geologic Time Scale
Earliest fossil record of lifeSlide15
Plate Tectonics
Fig. 15.8, p. 462Slide16
Geologic Record
Fig. 15.10, p. 463
Glacial ice volume from deep-sea sediment oxygen isotope analysis
Temperature variation from ice core oxygen isotope analysisSlide17
The Last Glacial Maximum
Fig. 15.9, p. 463
Occurred 20-18 thousand years agoSlide18
Glacial/Interglacial Climatic Episodes
Fig. 15.11, p. 464
Younger
DryasSlide19
Lessons of the Climate Past
Climate is inherently variable over a large range of time scales (years, decades, centuries, millennia)
Variations in climate are geographically non-uniform in both sign (direction) and magnitude
Climate change may consist of a long-term trend in various climate elements and/or a change in the frequency of extreme weather eventsSlide20
Lessons of the Climate Past (cont’d)
Climate change tends to be abrupt rather than gradual
(change is faster than duration)
Only a few cyclical variations can be discerned from the long-term climate record
Regular cycles: diurnal and seasonal variations, incoming solar radiation
Quasi-regular variations: El Ni
ñ
o,
Holocene millennial-scale fluctuations, major glacial-interglacial shifts
Climate change impacts society