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Overview of Climate Change

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Overview of Climate Change Throughout Earth History During the Phanerozoic (600 Ma), climate fluctuated between What were the possible causes of warm-cool modes ... – PowerPoint PPT presentation

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Title: Overview of Climate Change


1
Overview of Climate Change Throughout Earth
History
  • During the Phanerozoic (600 Ma), climate
  • fluctuated between

2
What were the possible causes of warm-cool modes
during the Phanerozoic?
(think plate tectonics)
which would have altered ocean
and atmosphere circulation
3
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
4
Cretaceous period (100 Ma)
  • continents were located
  • existed
  • temperatures were

5
Tertiary period
  • uplift of Rocky Mtns. and Himalayas

6
Quaternary period (1.8 Ma to present)
  • Pleistocene epoch (1.8 Ma to 11.5 Ka)
  • -- climate marked by a

7
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
8
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.

9
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10
g. melting of ice sheets began 17 Ka and
continued at an uneven pace
11
  • 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

12
--the 3-dimensional circulation of the oceans
it is driven by salinity and temperature
differences
cross-section view of ocean circulation in the
Atlantic
13
  • the THC and surface ocean currents combine
  • to create a of
  • three-dimensional oceanic circulation

14
Downwelling of cold, salty water in the
North Atlantic pulls surface waters further
north than they normally would travel this is
termed
15
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
16
What could cause freshwater inputs to the
North Atlantic to increase?
17
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18
during the Hypsithermal than today
19
temps were warmer than present in some areas
20
  • climate much colder than present (though not a
  • true ice age)
  • glaciers advanced in Europe, N. America,
  • Africa, New Zealand
  • Vikings
  • abandoned
  • Greenland
  • settlements

21
from 13.6º C to 14.4º C (56.8º F to 57.6º F)
22
From 2007 IPCC Report
23
  • Over long time periods,
  • climate is not stable!
  • Statements about climate
  • depend on the time
  • scale you are considering.

24
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?
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