climate and climate change 17 january 2011. how and why does climate change? climate changes over a...
TRANSCRIPT
Climate and Climate Change
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– Regular changes in Earth’s orbit– Volcanic eruptions– Changes in Earth’s surface characteristics– Human activities
Climate Definition
• Weather of a locality averaged over a time period– 30 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.html
Climatic Anomalies• Departure from long-term climatic average of
the average for a particular week, month, or year
• Precipitation 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 patterns
Temperature Anomalies – US, Dec 2007
Precipitation Anomalies – US, Dec 2007
Climate Boundary Conditions
• Climate determine by conservation of energy and conservation of mass
• Climates 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 106-108 years
January Mean Sea-level Air Temperature (C)
Fig. 15.3, p. 455
July Mean Sea-level Air Temperature (C)
Fig. 15.4, p. 456
Mean Annual Precipitation (mm)
Fig. 15.5, p. 458
Köppen Climate
Classifications
Letters h, k and a, b, c, d indicate relative warmth, coolness
See Appendix III, p. 509-515
Table, p. 510
Earth’s Climate Record
Based on• Historical documents• Fossil plants and animals• Pollen profiles• Tree growth rings• Glacial ice cores• Deep sea sediment cores
Geologic Time Scale
Plate tectonics complicates climate reconstruction
Fig. 15.6, p. 460
Geologic Time Scale
4030
6567
3048 40
34
41 37
64 78
8.2
21.2 12.9 18.4 3.6 1.69 0.01
PrecambrianCambrianOrdovicianSilurianDevonianMississippianPennsylvanianPermianTriassicJurassicCretaciousPaleoceneEoceneOligoceneMiocenePliocenePleistoceneHolocene
Earliest fossil record of life
Plate Tectonics
Fig. 15.8, p. 462
Geologic Record
Fig. 15.10, p. 463
A. Glacial ice volume from deep-sea sediment oxygen isotope analysis
B. Temperature variation from ice core oxygen isotope analysis
The Last Glacial Maximum
Fig. 15.9, p. 463
Occurred 20-18 thousand years ago
Glacial/Interglacial Climatic Episodes
Fig. 15.11, p. 464
Younger Dryas
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 events
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 recordRegular cycles: diurnal and seasonal variations,
incoming solar radiationQuasi-regular variations: El Niño, Holocene
millennial-scale fluctuations, major glacial-interglacial shifts
• Climate change impacts society