Overview of Climate Change

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Overview of Climate Change Throughout Earth
History

• During the Phanerozoic (600 Ma), climate
• fluctuated between

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What were the possible causes of warm-cool modes
during the Phanerozoic?
(think plate tectonics)
which would have altered ocean
and atmosphere circulation
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Proxy data used to study Phanerozoic climates
? e.g., halite, gypsum indicate that
a warm-dry climate prevailed when and
where these rocks formed
? indicate a warm, humid climate
? old glacial deposits preserved in
ancient rocks
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Cretaceous period (100 Ma)

• continents were located

• existed

• temperatures were

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Tertiary period

• uplift of Rocky Mtns. and Himalayas

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Quaternary period (1.8 Ma to present)

• Pleistocene epoch (1.8 Ma to 11.5 Ka)
• -- climate marked by a

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Pleistocene (contd)

• glacials 90,000 yr
• interglacials 10,000 yr

a. continental ice sheets up to 3 km
thick covered N. Am. And N. Eurasia
(LGM) 18 Ka
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b. expanded in the Rocky Mountains and
other parts of the world
c. in the N. Hemisphere ranged 10º
latitude further south than present
d. oceans were 2º C cooler than today

• air temperatures 1-12º C cooler, depending on
  location
• f.

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g. melting of ice sheets began 17 Ka and
continued at an uneven pace
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• the YD started

• many climate scientists believe that the abrupt
• cooling and warming at the beginning
• and end of the YD was cause by a shut-
• down of the

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--the 3-dimensional circulation of the oceans
it is driven by salinity and temperature
differences
cross-section view of ocean circulation in the
Atlantic
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• the THC and surface ocean currents combine
• to create a of
• three-dimensional oceanic circulation

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Downwelling of cold, salty water in the
North Atlantic pulls surface waters further
north than they normally would travel this is
termed
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Is the Atlantic Heat Pump constant?
NO!

• downwelling of water is controlled by water
• density

• if less dense freshwater is added to the North
• Atlantic, it will not sink as rapidly,
  resulting
• in a

have been blamed for the rapid temp. changes
of the YD
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What could cause freshwater inputs to the
North Atlantic to increase?
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during the Hypsithermal than today
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temps were warmer than present in some areas
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• climate much colder than present (though not a
• true ice age)
• glaciers advanced in Europe, N. America,
• Africa, New Zealand
• Vikings
• abandoned
• Greenland
• settlements

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from 13.6º C to 14.4º C (56.8º F to 57.6º F)
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From 2007 IPCC Report
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• Over long time periods,
• climate is not stable!

• Statements about climate
• depend on the time
• scale you are considering.

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Deep thoughts

• Is the recent warming caused by increased
  greenhouse gases (CO2) in the atmosphere?

• How much warming will occur in the next
• 100-200 yr?

• What should be done, if anything, to address
  global warming?