CLIMATE CHANGE OVER
THE LAST TWO MILLION YEARS
1. Introduction: forcings and feedbacks
2. Standing on the shoulders of giants:
development of the Milankovitch theory
3. Evidence from the oceans, evidence from the ice
4. Pleistocene and Holocene
5. Abrupt climate change
Basic components of the climate system.
Source: Ruddiman, 2001, p. 9.
Scientific ideas are continually tested
and improved over time.
“If I have seen further, it is by standing
on the shoulders of giants.”
Sir Isaac Newton, 1676.
How was this formed??
Lauterbrunnen, Switzerland.
Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,
http://www.swisseduc.ch/glaciers/glossary/index-en.html
Why is this here??
Erratic boulders, Switzerland.
Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,
http://www.swisseduc.ch/glaciers/glossary/index-en.html
How were these formed??
Lateral moraines, Switzerland.
Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,
http://www.swisseduc.ch/glaciers/glossary/index-en.html
Louis Agassiz, 1807-1873.
Source: Riebeek, 2005, http://earthobservatory.nasa.gov/Features/Paleoclimatology/
Not to be confused with Andre Agassi.
Louis Agassiz, 1807-1873.
Source: Riebeek, 2005, http://earthobservatory.nasa.gov/Features/Paleoclimatology/
How was this formed??
Lauterbrunnen, Switzerland.
Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,
http://www.swisseduc.ch/glaciers/glossary/index-en.html
Why is this here??
Erratic boulders, Switzerland.
Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,
http://www.swisseduc.ch/glaciers/glossary/index-en.html
How were these formed??
Lateral moraines, Switzerland.
Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,
http://www.swisseduc.ch/glaciers/glossary/index-en.html
Switzerland under ice. Source: Swiss Federal Office of Topography
The last glacial maximum (“ice age”).
Cyclical wobbles in the Earth’s orbit: from
Adhemar to Croll to Milankovitch.
Source: Houghton, 2009, p. 86.
Source: Mann and Kump, 2009, p. 63.
Source: Mann and Kump, 2009, p. 63.
Source: Mann and Kump, 2009, p. 63.
Cyclical wobbles in the Earth’s orbit.
Source: Archer, 2012, p. 96.
Cyclical wobbles in the Earth’s orbit.
Source: Archer, 2012, p. 95.
Put ‘em together and what have you got?
Small differences between the extremes lead to glacial periods,
roughly one every 100,000 years.
Source: Encyclopedia of the Earth.
The biological pump in the oceans
ATMOSPHERE
OCEAN
~100 m mixed layer
Wee beasties soak up carbon
~4900 m deep water
Bodies, shells and skeletons
sink to ocean floor
The biological pump in the oceans
ATMOSPHERE
OCEAN
Wee beasties soak up carbon
Bodies, shells and skeletons
sink to ocean floor
Lots (and lots) of different species of zooplankton.
Source: Tohoku University Museum, http://webdb2.museum.tohoku.ac.jp/e-foram/
A STEP BACK:
REMINDER ABOUT
THE NATURE OF MATTER
THE NATURE OF MATTER:
Elements and compounds, atoms and molecules.
Chemical element: A pure chemical substance composed
of atoms with the same number of protons in the atomic
nucleus.
Chemical compound: A pure chemical substance
consisting of two or more different chemical elements
that can be separated into simpler substances by
chemical reactions.
Source: International Union of Pure and Applied Chemistry Compendium of Chemical
Terminology (Gold Book), http://goldbook.iupac.org/index.html.
Schematic showing the structure of an oxygen atom.
8 electrons (-)
Nucleus:
8 protons (+)
(= atomic number)
THE NATURE OF MATTER:
Elements and compounds, atoms and molecules.
Isotope: Atoms of the same element having the same
atomic number but different mass numbers (atomic
mass).
Source: Mann and Kump, 2009, p. 201.
Schematic showing the structure of an oxygen atom.
8 electrons (-)
Nucleus:
8 protons (+)
8, 9, or 10 neutrons
Atomic number = 8
Atomic mass (mass number) = 16, 17 or 18 (16O, 17O or
18O)
Two isotopes
of oxygen:
16O
18O
H216O
H218O
Which water molecules fall
as snow near the poles?
Which water molecules
rain out more easily?
Which water molecules
evaporate more easily?
Bigger ice sheets separate out the isotopes
More 16O locked up in the ice sheets
More 18O remains in the oceans
Sea floor and ice core records of temperature.
Source: Houghton, 2009, p. 83.
Ocean sediments
Vostok ice core
How ice coring works
Source: Ruddiman, 2001.
NorthGRIP European ice coring project on Greenland.
Source: NorthGRIP website, http://www.gfy.ku.dk/~www-glac/ngrip/index_eng.htm
Section of NorthGRIP ice core.
Source: NorthGRIP website, http://www.gfy.ku.dk/~www-glac/ngrip/index_eng.htm
Temperature relative to present (Celsius)
Temperature derived from Vostok ice core:
hydrogen isotope analysis (deuterium).
Years before present
Source: drawn using Vostok ice core data first published by JR Petit, available from World Data
Center for Paleoclimatology, http://hurricane.ncdc.noaa.gov/pls/paleo/ftpsearch.icecore
Sea floor and ice core records of temperature.
Source: Houghton, 2009, p. 83.
Some problems with basic Milankovitch theory:
1. Small forcing, large response
2. Symmetrical forcing, asymmetrical (saw-toothed)
response
3. Identical response in northern and southern
hemispheres
Temperature relative to present (Celsius)
Temperature derived from Vostok ice core:
hydrogen isotope analysis (deuterium).
Years before present
Source: drawn using Vostok ice core data first published by JR Petit, available from World Data
Center for Paleoclimatology, http://hurricane.ncdc.noaa.gov/pls/paleo/ftpsearch.icecore
Some problems with basic Milankovitch theory:
1. Small forcing, large response
2. Symmetrical forcing, asymmetrical (saw-toothed)
response
3. Identical response in northern and southern
hemispheres
FORCING
RESPONSE
What general concept might help explain this??
Sea floor and ice core records of temperature.
Source: Houghton, 2009, p. 83.
CARBON DIOXIDE/TEMPERATURE FEEDBACK
Arrange the terms and connect with arrows
Goes up/down
ORBITAL WOBBLES
(Milankovitch forcing)
CO2 IN ATMOSPHERE
CO2 RELEASED
FROM OCEANS
TEMPERATURE
CARBON DIOXIDE/TEMPERATURE FEEDBACK
ORBITAL WOBBLES
(Milankovitch forcing)
CO2 IN
ATMOSPHERE
Goes up
TEMPERATURE
CO2 RELEASED
FROM OCEANS
Temperature sometimes leads carbon dioxide
Temperature and CO2 in the Vostok ice core
Carbon dioxide (ppm)
290
4
2
~800 yr. lag
270
0
250
-2
CO2
230
-4
210
-6
Temperature
190
-8
170
150
Temperature relative
to present (Celsius)
310
-10
259000
254000
249000
244000
Years before present
239000
-12
234000
Source: data from WDC
Paleoclimatology
CARBON DIOXIDE/TEMPERATURE FEEDBACK
At multi-million year timescales, the feedback is:
negative
At 100,000-year timescales, the feedback is:
positive
Pleistocene and Holocene
Holocene:
the last
10,000 years
Temperature relative to present (Celsius)
Pleistocene: from ~2.5 million to 10,000 years ago
Years before present
10,000 years ago
Source: drawn using Vostok ice core data first published by JR Petit, available from World Data
Center for Paleoclimatology, http://hurricane.ncdc.noaa.gov/pls/paleo/ftpsearch.icecore
Central Greenland temperature estimated from GISP 2
stable isotopes
WARM
Holocene
Central Greenland temperature
(Celsius)
Pleistocene
Years before present
COLD
Source: drawn using GISP2 ice core data first published by Richard Alley, available from World
Data Center for Paleoclimatology, http://hurricane.ncdc.noaa.gov/pls/paleo/ftpsearch.icecore
Abrupt climate changes in the ice core record:
Dansgaard-Oeschger events and the Younger Dryas
WARM
Dansgaard-Oeschger events
Younger Dryas,
12 to 10.7 kyr BP
Years before present
Central Greenland temperature
(Celsius)
GISP 2 Central Greenland temperature
COLD
Source: drawn using GISP 2 ice core data first published by Richard Alley, available from World
Data Center for Paleoclimatology, http://hurricane.ncdc.noaa.gov/pls/paleo/ftpsearch.icecore
“If you're living with an angry beast,
you shouldn't poke it with a sharp stick.”
Wallace Broecker, 2008
Is this a good idea?
The Valley of Gwangi, Warner Bros., 1969.
This assumes that humans can act as a
forcing on the global climate system.
IS THIS A REASONABLE ASSUMPTION?