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Climate and Climate Change 17 January 2011
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Page 1: 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,

Climate and Climate Change

17 January 2011

Page 2: 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,

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

Page 3: 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,

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

Page 4: 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,

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

Page 5: 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,

Temperature Anomalies – US, Dec 2007

Page 6: 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,

Precipitation Anomalies – US, Dec 2007

Page 7: 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,

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

Page 8: 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,

January Mean Sea-level Air Temperature (C)

Fig. 15.3, p. 455

Page 9: 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,

July Mean Sea-level Air Temperature (C)

Fig. 15.4, p. 456

Page 10: 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,

Mean Annual Precipitation (mm)

Fig. 15.5, p. 458

Page 11: 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,

Köppen Climate

Classifications

Letters h, k and a, b, c, d indicate relative warmth, coolness

See Appendix III, p. 509-515

Table, p. 510

Page 12: 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,

Earth’s Climate Record

Based on• Historical documents• Fossil plants and animals• Pollen profiles• Tree growth rings• Glacial ice cores• Deep sea sediment cores

Page 13: 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,

Geologic Time Scale

Plate tectonics complicates climate reconstruction

Fig. 15.6, p. 460

Page 14: 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,

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

Page 15: 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,

Plate Tectonics

Fig. 15.8, p. 462

Page 16: 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,

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

Page 17: 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,

The Last Glacial Maximum

Fig. 15.9, p. 463

Occurred 20-18 thousand years ago

Page 18: 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,

Glacial/Interglacial Climatic Episodes

Fig. 15.11, p. 464

Younger Dryas

Page 19: 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,

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

Page 20: 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,

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


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