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(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Historical Perspectives Historical Perspectives onon
Climate Change ResearchClimate Change Research
Primary Source:
IPCC WG-I Chapter 1 - Historical Overview of Climate Change Science
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
The Scientific BasisThe 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)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
How Do Climate Scientists Conduct Experiments?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
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Rigorous Review is Essential!Rigorous Review is Essential!
Growth in the Peer-Reviewed LiteratureGrowth in the Peer-Reviewed Literature
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Rigorous Review is Essential!Rigorous Review is Essential!
Growth in the Peer-Reviewed LiteratureGrowth in the Peer-Reviewed Literature
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
What Determines Earth’s Climate?What Determines Earth’s Climate?
Earth’s Orbit
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Earth’s Orbital ParametersEarth’s Orbital Parameters
Perihelion(~ Jan 3)
Vernal Equinox (~ March 21)
Aphelion(~ July 5)
Why is Iowa colder in January?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Earth’s Orbital ParametersEarth’s Orbital Parameters
Eccentricity = SQRT(a2 - b2)/a ; for circle, = 0
Longitude of perihelion (one choice: angle from NH vernal equinox)
Tilt of rotation axis (obliquity)
b
a
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
What Determines Earth’s Climate?What Determines Earth’s Climate?
Earth’s OrbitEarth’s Albedo Earth’s Emissions
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect: Early DiscoveriesThe 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)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect: Atmospheric The Greenhouse Effect: Atmospheric Properties & Climate ChangeProperties & 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)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
The Greenhouse Effect: Impact of Humans?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)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Other Atmospheric ConstituentsOther 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)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
The Climate SystemThe Climate System
How do we simulate this?How do we simulate this?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Development of Development of Global Climate Global Climate Models (GCMs)Models (GCMs)
What is this?
Increased computing power has allowed increased resolution …
Computing demand Computing demand increases inversely with increases inversely with cubecube of horizontal of horizontal resolution.resolution.
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Development of Development of Global Climate Global Climate Models (GCMs)Models (GCMs)
… and increasing complexity.
Which should be Which should be favored?favored?
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Complements to GCMsComplements to GCMs
Global stretched-grid modelsGlobal stretched-grid models
Regional (limited-area) Regional (limited-area) modelsmodels
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
Example Regional Model DomainExample Regional Model Domain
Contrast the Hadley Centre GCM …Contrast the Hadley Centre GCM …
2.5˚ (lat) x 3.75˚ (lon)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
… … with a regional modelwith a regional model
~ 0.5˚ (lat) x ~ 0.5˚ (lat) x ~ 0.5˚ (lon)~ 0.5˚ (lon)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
How Well Have GCMs performed?How Well Have GCMs performed?
One test: One test: Projected changes Projected changes in global in global temperaturetemperature
T [
˚C]
Much more detail later (AR4, Chapter 8)
(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) History (from IPCC WG-I, Chapter 1)History (from IPCC WG-I, Chapter 1)
ENDEND
Historical Perspectives Historical Perspectives onon
Climate Change ResearchClimate Change Research