Ice Time

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Ice Time

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Erratics and moraines
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Erratics
such obvious mechanical absurdities William
Hopkins
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Scratches in rocks
Could scratches and polish just be due to ice?
Robert Murchison
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Fjords
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Glacier in Switzerland
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Glacier moraine
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Stages of scientific discovery first, people
deny that it is true then they deny that it is
important finally they credit the wrong person.
Alexander von Humboldt
Karl Shimper
Jean de Charpentier
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History of Climate on Earth

• The photograph taken in 1928, above, shows how
  the Upsala Glacier, part of the South American
  Andes in Argentina, used to look. The ice on the
  Upsala Glacier today, shown in 2004 below, is
  retreating at least 180 ft. per year

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Climate over past 600 million years
Coal Deposits Desert Deposits Tropical
Soils Glacial Material Plant and animal fossils
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Ice Core Data (past 400,000 yrs)
Bottom line Climate can be stable and regular
for long periods of time, But sometimes it can
also go crazy (in a big way) as the result of
modest causes.
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Depiction of recent ice age
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Current location of continents and glaciers
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Causes of Climate Change

• Amount of energy given off by sun
• Orbital variations (Croll)
• Spin variations (Milancovich)
• Plate tectonics (continents rearranging)
• Snow White
• Greenhouse gases

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Solar energy output

• Solar output increasing over Suns lifetime
• Sun currently gives off 30 more energy than 4.5
  billion years ago
• Liquid water not stable on Earth 2 billion years
  from now!
• Solar cycle and changes in solar activity
• Maunder Minimum low sunspot activity may have
  influenced Little Ice Age (17th century)

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Sun is more active when it has sunspots
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Does the sun give off more or less energy when
it has fewer sunspots?
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Orbital and spin variations

• Croll-Milankovitch cycles
• Why werent these guys taken seriously?
• Why did mainstream scientists resist these ideas?
• Eccentricity (Croll)
• Shape of orbit changes (100,000 yrs)
• Tilt (Milankovitch)
• Tilt changes, not always 23.5 degrees (41,000
  yrs)
• Precession
• Direction of the tilt changes (20,000 yrs)

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Orbit changes affect the tilt of the Earths spin
axis. The tilt (called the obliquity) is the
reason for seasons.
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Where is the Sun throughout the year?
zenith
and Sept 21 (Autumnal Equinox)
east
west
south
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Add all 3 cycles together, whats that spell?
Croll-Milankovitch Cycle
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Continental Drift

• Plate tectonics causes continents to drift
• Location of continents and oceans affects climate
• Himalayas Isthmus of Panama
• http//www.scotese.com/paleocli.htm

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The Snow White Effect

• If part of the Earth is covered with snow, it
  reflects away sunlight, so Earth gets cooler
• A possible runaway effect

Ice ages change very quickly 1) Biggest factor
for ice ages how cool the summers are, not how
brutal the winters are 2) If ice doesnt melt
over summer, less sunlight absorbed and it gets
colder Feedback loops (positive and negative)
can enhance or dampen climate changes
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Snowball Earth Hypothesis Frozen up to 2.2
billion years ago, million year thaw, then bigger
ice age (super ice age) Temperatures may have
dropped up to 80 degrees Fahrenheit Ocean froze
over completely? What kept some life going? Some
open water over hotspot? Translucent ice? How
did we get out of snowball earth? Volcanoes?
Pushed through ice and released greenhouse
gases? Correlates with 650 million years ago and
Cambrian explosion, more on this later
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Causes of Climate Change

• Amount of energy given off by sun
• Maunder Minimum
• Orbital and spin variations
• Croll-Milankovitch cycles
• Precession, obliquity, eccentrity
• Plate tectonics
• Location of continents
• Himalayas Isthmus of Panama
• Snow White effect
• Greenhouse gases
• Greenhouse gases affect flow of energy through
  atmosphere

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To understand how a greenhouse works, you need to
know Wiens law The hotter something is,
the shorter the wavelength that it glows
(or radiates) at. Some things (like white)
reflect light better than others (like
black). Some things scatter light (depending on
the wavelength). Pay attention to
the blackboard!
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Energy Budget Every planet heats up just
enough so that it can radiate energy out (IR)
to balance the solar energy coming in (IR
visible light) If there is an atmosphere, that
is where the planets radiation exits into space.
So the atmospheres temperature matters for
balancing the budget. The surface gets much
warmer because it gets energy from the Sun
plus some of the IR from the atmosphere
(greenhouse effect). Is the greenhouse effect
good or bad for us? As discussed later The
warmed surface radiates back up to the
atmosphere. The surface gets hot enough that it
radiates just right to maintain the
balance. Bottom line the surface is warmer
than it would be without the atmosphere acting
like a greenhouse
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Which of the following appear to have a
greenhouse effect?
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Wiens Law

• Terrestrial spectrum peaks in IR around 10
  microns (.01mm)
• Sun radiates mostly visible and IR
• Earth radiates mostly IR

SUNLIGHT
EARTHLIGHT
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Wavelength Dependent Absorption

• Greenhouse gases (H20, CO2, CH4, other)
• Absorb different wavelengths of light
• Transmit visible light
• Absorb and re-emit IR

http//www.ucar.edu/learn/1_3_1.htm
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Atmosphere Absorption Spectrum

• Very little absorption at visible wavelengths
• Absorption of UV by ozone in upper atmosphere
• Absorption of IR by greenhouse gases in lower
  atmosphere

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Greenhouse gases keep IR from transmitting
directly out to space

• The Greenhouse Effect

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Greenhouse Effect Animation

• http//www.colorado.edu/physics/phet/
• http//dev.cadre.com.au/Astro_V/Project/Contact_Li
  st/

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Understanding the Greenhouse Effect (GHE)

• Effective Temperature
• Surface of Earth would be much colder w/out GHE
• Spectra for sun and earth
• Sun peaks in visible Earth peaks in IR
• Greenhouse gases absorb at different wavelengths
• H20, CO2, CH4
• Transparent at visible wavelengths
• Absorb and re-emit IR
• Surface temperature of planet raised above
  effective temperature
• Surface of planet is heated by energy radiated
  from the Sun AND energy re-radiated from the
  atmosphere

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Common Greenhouse Effect (GHE) Misconceptions

• GHE is related to ozone depletion.
• GHE involves reflected sunlight.
• GHE is new phenomenon on Earth.
• GHE is harmful to life.
• GHE on Earth is intermediate between that on Mars
  and Venus due to distance from sun.
• GHE is caused by smog and air pollution.
• GHE is same as global warming.

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Human-induced Greenhouse Effect

• Caused by humans
• Increased levels of CO2 from burning of fossil
  fuels during industrial revolution to present
• 1.5F (0.8 C) temperature increase over past 150
  years

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Population is dramatically increasing
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CO2 levels rising from emissions related to
transportation, energy, industry, and
deforestation
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Global temperatures are rising
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Time before present (thousands of years)
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The Earths atmosphere is very unstable. Small
things can have big effects. For the past few
thousand years, the climate has been relatively
steady, not too hot, not too cold, explaining in
part why civilization has been so successful. We
are changing the amount of an important
greenhouse gas, by putting CO2 back into the
air. Is this a good idea? Its not nice to fool
with Mother Nature