Historical Perspectives
on
Climate Change Research
Primary Source:
IPCC WG-I Chapter 1 - Historical Overview of Climate Change Science
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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)?
2. Basis for scientific progress
- builds on previous work
- self-correcting
3.
•
•
•
•
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?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
How Do Climate Scientists Conduct Experiments?
• There is only one planet.
• How can one test hypotheses?
1. Observed behavior (e.g., shortterm climate perturbations, like
volcanic emissions)
2. Simulation models
3. Fundamental theory
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Rigorous Review is Essential!
Growth in the Peer-Reviewed Literature
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Rigorous Review is Essential!
Growth in the Peer-Reviewed Literature
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
What Determines Earth’s Climate?
Earth’s Orbit
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Earth’s Orbital Parameters
Vernal Equinox
(~ March 21)
Aphelion
(~ July 5)
Perihelion
(~ Jan 3)
Why is Iowa
colder in
January?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Earth’s 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)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
What Determines Earth’s Climate?
Earth’s Albedo
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
Earth’s Orbit
Earth’s Emissions
History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect: Early Discoveries
Edme Marriotte (1620-1684):
Sun’s 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)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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 ~ 4˚C.) Human CO2
emissions could prevent another ice age.
Nobel Prize - Chemistry (1903)
(en.wikipedia.org)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect: Impact of Humans?
Guy Stuart Callendar (1897-1964)
2xCO2  T ~ 2˚C
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:
1. Overlap of H2O and CO2 absorption
bands  saturation  no impact of
increasing CO2.
2. Earth regulates CO2 amounts, esp.
via ocean. Humans have negligible
impact.
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
The Climate System
How do we simulate this?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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 …
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Development of
Global Climate
Models (GCMs)
… and increasing
complexity.
Which should be
favored?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Complements to GCMs
Global stretched-grid models
Regional (limited-area)
models
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Example Regional Model Domain
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
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)
… 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)
How Well Have GCMs performed?
T [˚C]
One test:
Projected changes
in global
temperature
Much more detail later
(AR4, Chapter 8)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)
Historical Perspectives
on
Climate Change Research
END
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)
History (from IPCC WG-I, Chapter 1)