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Transcript of Volcanoes and Ice Ages Causes of Natural Variability PowerPoint 97 To download: Shift LeftClick...
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Volcanoes and Ice Ages
Causes of Natural Variability
PowerPoint 97To download: Shift LeftClick
Please respect copyright on this material
![Page 2: Volcanoes and Ice Ages Causes of Natural Variability PowerPoint 97 To download: Shift LeftClick Please respect copyright on this material.](https://reader035.fdocuments.in/reader035/viewer/2022062408/56649e695503460f94b66319/html5/thumbnails/2.jpg)
Key Points Past Variations in Global Temperature
– 100 yrs Warming + Volcanoes– 1000 yrs Medieval Optimum + Little Ice age– 10,000 yrs Post glacial– 1,0000,000 yrs Milankovitch Cycles
Volcanoes
Climate records from ice and sediment cores
Ice ages
Worldwide, most small glaciers are receding
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El Nino Events and Global Temperature
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The last 1,000 years
Note +/- 0.5 oC
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South Western U.S. 1300 AD Why did these communities collapse?
Mesa Verde Cliff House
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Since the end of the last ice age Note range of +/- 1 oC since 10,000 BP
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Last Glacial Maximum
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Signs of Past Glaciation
xxx
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A million years of ice ages and interglacials
Estimated global surface temperature from ocean sediments
Present temperature 15 oC
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Key Points Past Variations in Global Temperature
Volcanoes– Large volcanoes inject sulfate aerosols into
stratosphere– Sulfate aerosols reflect sunlight back to space– Cool the earth, but only for a year
Climate records from ice and sediment cores
Ice ages
Worldwide, most small glaciers are receding
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Mount Saint Helens
May 18, 1980
United States Geological Survey
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Atmospheric TransmissionInterrupted by large volcanoes
El ChichonMountPinetubo
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Global temperature and volcanoes
Each event followed by a drop for 2-3 years
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Key Points
Past Variations in Global Temperature
Volcanoes
Climate records from ice and sediment cores O18 (temperature), CO2, sulfate, ...
Ice ages
Worldwide, most small glaciers are receding
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Drilling Ice Cores in Peru Annual layers in the
Quelccaya Ice Cap
Distant view of ice cap
Lonnie Thompson
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Inca Country
Peru
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Equator
Peru
Lonnie Thompson &Ellen Mosely Thompson
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AnnualSignature
in O18
Quelccaya - 1976 Core Also measured are dust,
and sulfate CO2 , methane can also
be measured from ice cores, though not from this one
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Drilling Ice Cores in
Greenland
xxx
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Key Points Past Variations in Global Temperature
Volcanoes
Climate records from ice and sediment cores
Ice ages– Last ice age ended 12,000 years ago– Changes over tens of thousands of years – Driven by Milankovitch cycles in Earth orbit– Recent evidence of abrupt transitions within 100
years
Worldwide, most small glaciers are receding
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A million years of ice ages and interglacials
Estimated global surface temperature from ocean sediments
Present temperature 15 oC
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Land Ice in the Northern Hemisphere (now vs 18,000 BP)
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Alaskan Glacier
Photo Inge Bretherton
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Greenland Ice Sheet
More great pictures (University of Cincinnati)
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Key Points Past Variations in Global Temperature
Volcanoes
Climate records from ice and sediment cores
Ice ages– Last ice age ended 12,000 years ago– Changes over tens of thousands of years – Driven by Milankovitch cycles in Earth orbit– Recent evidence of abrupt transitions within 100
years
Worldwide, most small glaciers are receding
![Page 26: Volcanoes and Ice Ages Causes of Natural Variability PowerPoint 97 To download: Shift LeftClick Please respect copyright on this material.](https://reader035.fdocuments.in/reader035/viewer/2022062408/56649e695503460f94b66319/html5/thumbnails/26.jpg)
Milankovitch Cycles Small, predictable, changes in orbit of Earth
around the sun Departures from idealized elliptic orbit of
Newton, Kepler Precession: period 23,000 years Tilt: period 41,000 years Ellipticity: period 100,000 years Calculated in 1920’s but then no evidence Do not change total radiation reaching earth,
only distribution among seasons
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Elliptic Orbit (Newton)
Ellipticity exaggerated For small sun, earth, orbit is fixed in space
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Tilt
No tilt, no seasons
Present tilt 23.5o
Varies 22o - 24.5o
every 41,000 years
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Precession - 1
Earth’s axis of rotation moves in space Because earth not quite spherical
– like a spinning top Earth now closest to sun in Northern
winter was/ will be in Northern summer
Period 23,000 years– About 12,000 years ago Hudson Bay ice cap
melted
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Precession - 2
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Incoming solar radiation Tilt + precession + ellipticity Varies with latitude Direct effects largest for continents
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Key Points
Past Variations in Global Temperature
Volcanoes
Climate records from ice and sediment cores
Ice ages
Worldwide, most small glaciers are receding
![Page 33: Volcanoes and Ice Ages Causes of Natural Variability PowerPoint 97 To download: Shift LeftClick Please respect copyright on this material.](https://reader035.fdocuments.in/reader035/viewer/2022062408/56649e695503460f94b66319/html5/thumbnails/33.jpg)
Evidence for Ice Cap
Melting
1976 - Right– Clear annual
trace 1991 - Left
– Warmed and melted
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Melting Glaciers
xxx
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Key Points
Past Variations in Global Temperature
Volcanoes
Climate records from ice and sediment cores
Ice ages
Worldwide, most small glaciers are receding
![Page 36: Volcanoes and Ice Ages Causes of Natural Variability PowerPoint 97 To download: Shift LeftClick Please respect copyright on this material.](https://reader035.fdocuments.in/reader035/viewer/2022062408/56649e695503460f94b66319/html5/thumbnails/36.jpg)
Sources of Information
Horel & Geisler Chapter 4,5 Lonnie Thompson and Ellen Mosely-
Thompson, Ohio State Universityhttp://polarmet.mps.ohio-state.edu/Icecore/Quelccaya.html
Thomas Lowell, University of Cincinnati http://tvl1.geo.uc.edu/ice/glacier.html