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Feb. 17, 1993. Climate Change. Feb. 21, 2000. Photo of glacial retreat on Mount Kilimanjaro (Feb. 1993 to Feb. 2000) from Wikipedia; Map of Africa from www.admin.uio.no. Weather Patterns are Dynamic e.g. , monthly variation. Temperature. Image from Wikipedia (see “Climate”).

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Climate change l.jpg

Feb. 17, 1993

Climate Change

Feb. 21, 2000

Photo of glacial retreat on Mount Kilimanjaro (Feb. 1993 to Feb. 2000) from Wikipedia;

Map of Africa from www.admin.uio.no


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Weather Patterns are Dynamic

e.g., monthly variation

Temperature

Image from Wikipedia (see “Climate”)


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Weather Patterns are Dynamic

e.g., monthly variation

Precipitation

Image from Wikipedia (see “Climate”)


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Earth’s Climate is also Dynamic

Climate Change (or Variation) Characterizes Earth’s History

Climate Change – a shift of average weather across a region

Image from Wikipedia (see “Geologic temperature record”)


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Earth’s Climate is also Dynamic

Climate Change (or Variation) Characterizes Earth’s History

E.g., Eocene temperature was 4 – 6 °C warmer than today

Image from Wikipedia (see “Geologic temperature record”)


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Earth’s Climate is also Dynamic

Climate Change (or Variation) Characterizes Earth’s History

E.g., Eocene temperature was 4 – 6 °C warmer than today

Eocene on Ellesmere Island, far north Canada

Modern day on Ellesmere Island, far north Canada

Images from www.thecanadianencyclopedia.com


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Earth’s Climate is also Dynamic

Climate Change (or Variation) Characterizes Earth’s History

E.g., Eocene seas were 100 - 150 m higher than today

Image from www.thecanadianencyclopedia.com


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Earth’s Climate is also Dynamic

Climate Change (or Variation) Characterizes Earth’s History

E.g., Milankovitch Cycles –Earth’s changing orbit influences

temperature with ~41,000 & ~100,000 yr periodicities

Image from Wikipedia (see “Geologic temperature record”)


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Earth’s Climate is also Dynamic

Climate Change (or Variation) Characterizes Earth’s History

E.g., Pleistocene glacial and inter-glacial periods

Image from Wikipedia (see “Geologic temperature record”)


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Natural Climate “Forcing”

(Physical processes that influence Earth’s avg. temp.)

E.g., Pleistocene glacial and inter-glacial periods

Image from Wikipedia (see “Geologic temperature record”)


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Natural Climate “Forcing”

Orbital

Owing to other planets in our solar system, Earth’s orbit varies over long time scales;

e.g., eccentricity varies from 0.005 to 0.058

Hypothetical circular orbit, no eccentricity

Hypothetical orbit with0.5 eccentricity

Image from Wikipedia (see “Milankovitch cycles”)


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Natural Climate “Forcing”

Orbital

Earth’s axial tilt (obliquity) varies from 22.1° to 24.5°

Image from Wikipedia (see “Milankovitch cycles”)


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Natural Climate “Forcing”

Orbital

Orbital forcing causes variation in solar heating of the planet (a.k.a. radiative forcing)

Image from Wikipedia (see “Milankovitch cycles”)


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Natural Climate “Forcing”

Radiative

Image from Wikipedia (see Global Warming)


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Natural Climate “Forcing”

Radiative

Earth’s avg. temp. = 14 °C (57 °F)

Without the atmosphere’s greenhouse effect it would be about

-18 °C

(-0.4 °F)

Image from: www.grida.no


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Anthropogenic Causes of Climate Change

At regional scales, deforestation leads to drying (and heating),

owing primarily to reduced evapotranspiration and water-holding capacity of soil

This isn’t very surprising, since clouds that form from transpired water are absent over wide, treeless rivers & their immediate floodplains in the Amazon Basin

Image from: http://earthobservatory.nasa.gov


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Anthropogenic Causes of Climate Change

At regional scales, deforestation leads to drying (and heating),

owing primarily to reduced evapotranspiration and water-holding capacity of soil

E.g., cities in the Brazilian Amazon are warmer and drier than

those areas were before they became urban centers

E.g., much of Greece is warmer and drier today

because of deforestation in earlier millennia

These examples are not global, but they demonstrate that

humans can alter regional climate patterns


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Anthropogenic Causes of Climate Change

International Panel on Climate Change (IPCC)

est. 1988 by the United Nations

Taking all the accumulated evidence into account, anthropogenic increases in greenhouse gases are the principal causes of modern global warming; i.e., we are experiencing an anthropogenically enhanced greenhouse effect

Image from Wikipedia (see “Greenhouse gas”)


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Anthropogenic Causes of Climate Change

Al Gore

(b. 1948)

45th U. S. Vice President

Shared Nobel Peace Prize (2007) with IPCC

Academy Award (2007) for the documentary film:An Inconvenient Truth

Photo from: www.thegeneralist.co.uk


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Anthropogenic Causes of Climate Change

The Keeling Curve

Image from NOAA


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Anthropogenic Causes of Climate Change

IPCC predictions are for [CO2] by 2100:

500 to 1000 ppm;

with concomitant global temperatures 1.1 to 6.4 °C higher

Image from www.epa.gov


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Kyoto Protocol

Legally binding treaty (when ratified by states) that intends to achieve “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with

the climate system"

Green = signed & ratified

Red = signed, but not ratified

Grey =non-signatory

Image from Wikipedia (see “Kyoto Protocol”)


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Declining Glacial Thickness

Image from Wikipedia (see “Global Warming”)


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Feb. 17, 1993

Glacial retreat (loss) on

Mt. Kilimanjaro

Feb. 21, 2000

Photo of glacial retreat on Mount Kilimanjaro (Feb. 1993 to Feb. 2000) from Wikipedia;

Map of Africa from www.admin.uio.no


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Decreasing oceanic pH

Tatoosh Island, Washington

Photo from Wikipedia; figures from Wootton et al. 2008 Proceedings of the National Academy of Science


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Climate Change Impacts Biota

Altered expression of traits (owing to phenotypic plasticity;

e.g., phenology)

Range shifts (especially upslope and to higher latitudes)

Adaptation (to changing environment)

Extinctions (when range shifts and adaptation fail tokeep pace with changing environments)


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Climate Change Impacts Biota

Range map and image of polar bear (Ursus maritimus) from Wikipedia


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Opinions on Climate Change

Do you think human activity is a significant contributing

factor in changing mean global temperature?

From Doran & Zimmerman (2009) Eos (formerly Transactions of the American Geophysical Union)