Historical Perspectives on Climate Change Research

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Historical Perspectives onClimate Change
Research
Primary Source IPCC WG-I Chapter 1 -
Historical Overview of Climate Change Science
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The Scientific Basis
1. Hypothesis testing - Should be subject to
peer analysis review - Can it be shown, in
principle, to be false? - Can it provide
predictions (tests)?

• Basis for scientific progress
• - builds on previous work
• - self-correcting

• For IPCC Key questions
• Has it been rigorously tested?
• Did it appear in the peer-reviewed literature?
• Did it build on the existing research record
  where appropriate?
• What are the uncertainties?

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How Do Climate Scientists Conduct Experiments?

• There is only one planet.
• How can one test hypotheses?

1. Observed behavior (e.g., short-term climate
   perturbations, like volcanic emissions)
2. Simulation models
3. Fundamental theory

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Rigorous Review is Essential!
Growth in the Peer-Reviewed Literature
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Rigorous Review is Essential!
Growth in the Peer-Reviewed Literature
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What Determines Earths Climate?
Earths Orbit
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Earths Orbital Parameters
Vernal Equinox ( March 21)
Aphelion ( July 5)
Perihelion ( Jan 3)
Why is Iowa colder in January?
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Earths Orbital Parameters
b
a
Eccentricity SQRT(a2 - b2)/a for circle,
0 Longitude of perihelion (one choice angle
from NH vernal equinox) Tilt of rotation axis
(obliquity)
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What Determines Earths Climate?
Earths Orbit
Earths Albedo
Earths Emissions
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The Greenhouse Effect
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The Greenhouse Effect Early Discoveries
Edme Marriotte (1620-1684) Suns heat passes
through glass, other heat does not (1681).
(www.nndb.com)
Horace Bénédict de Saussure (1740-1799) Air in
mountains does not trap heat as much as air in
low-lying regions
(www.eoearth.org)
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The Greenhouse Effect Atmospheric Properties
Climate Change
John Tyndall (1820-1893) Measured infrared
radiation absorption properties of atmospheric
molecules Changing H2O or CO2 could cause all
the mutations of climate which the researches of
geologists reveal
(en.wikipedia.org)
Svante August Arrhenius (1859 -1927) 40 ? or ?
in CO2 could explain advance retreat of
glaciers. (2xCO2 ? ?T 4C.) Human CO2 emissions
could prevent another ice age. Nobel Prize -
Chemistry (1903)
(en.wikipedia.org)
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The Greenhouse Effect Impact of Humans?
Guy Stuart Callendar (1897-1964) 2xCO2 ? ?T
2C Must treat atmosphere as set of interacting
layers, not a single slab. Speculated, with
others, that ?T over first part of 20th Century
was anthropogenic.
(www.aip.org)

• Criticisms
• Overlap of H2O and CO2 absorption bands ?
  saturation ? no impact of increasing CO2.
• Earth regulates CO2 amounts, esp. via ocean.
  Humans have negligible impact.

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Other Atmospheric Constituents
Other Greenhouse Gases - Methane (CH4) -
Nitrous Oxide (N2O) - CFCs

• Anthropogenic Aerosols (particles)
• Scatter sunlight back to space
• Cause more, smaller cloud particles (increase
  albedo)

(oea.larc.nasa.gov)
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The Climate System
How do we simulate this?
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Development of Global Climate Models (GCMs)

• ? ? ?
• What is this?

Computing demand increases inversely with cube of
horizontal resolution.
Increased computing power has allowed increased
resolution
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Development of Global Climate Models (GCMs)
and increasing complexity.
Which should be favored?
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Complements to GCMs
Global stretched-grid models
Regional (limited-area) models
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Example Regional Model Domain
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Contrast the Hadley Centre GCM
2.5 (lat) x 3.75 (lon)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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with a regional model
0.5 (lat) x 0.5 (lon)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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How Well Have GCMs performed?
One test Projected changes in global temperature
?T C
Much more detail later (AR4, Chapter 8)
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END
Historical Perspectives onClimate Change
Research