Sensitivity Tests

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What is a "sensitivity test" ?


A climate model's prediction of temperatures, winds, moisture flux and other climate variables is dependent on the model physics (equations and parameterizations), initial conditions (temperatures, etc. at the start of the model calculations) and boundary conditions (geography, vegetation, atmospheric composition, solar forcing, u.s.w.).

In the real world, boundary conditions can both force climate and change in response to climate. In most climate models, including the GENESIS Earth System Model, used here, boundary conditions are static: They are set at the start of calculations and they can not change in response to climate. Boundary conditions are, in this case, only climate forcings.

In a climate model sensitivity test, some boundary condition, initial condition, or element of the model physics is changed and the new model is run to equilibrium (temperatures are not increasing or decreasing substantially anywhere). The new model steady-state result is then compared to results obtained before the change was made. In this way, it becomes clear what the sensitivity of the model result is to geography, or atmospheric carbon dioxide concentration, for example.

To view the results of several GENESIS model sensitivity tests, follow the links below.


Geography

What effect does changing land/sea distribution and continental elevations have on the climate model?
How much of the warmth of the Paleogene and late Cretaceous (relative to the modern climate) can be attributed to tectonic plate motions?

view boundary conditions input for 3 different geographies
view the model results for these 3 cases



Trace Gas Concentrations (in prep.)

How does the GENESIS model respond when the atmospheric concentrations of carbon dioxide, methane and nitrous oxide are increased?
How does the CO2-sensitivity of the model compare to that of coupled models used in the IPCC 4th Assessment Report?

Full experiments describing the precipitation d18O sensitivity to atmospheric composition are not yet published, but you can view previously published CO2 and CH4 sensitivity test results in a number of papers on my home page, most importantly:
Bice, K. L., D. Birgel, P. A. Meyers, K. A. Dahl, K. Hinrichs, and R. D. Norris (2006), A multiple proxy and model study of Cretaceous upper ocean temperatures and atmospheric CO2 concentrations, Paleoceanography, 21, PA2002, doi:10.1029/2005PA001203. pdf
Bice, K. L., B. T. Huber, and R. D. Norris (2003), Extreme polar warmth during the Cretaceous greenhouse?: Paradox of the Late Turonian d18O record at DSDP Site 511, Paleoceanography, 18, doi: 10.1029/2002PA000848. pdf
Bice, K. L., and R. D. Norris (2002), Possible Atmospheric CO2 extremes of the middle Cretaceous (late Albian-Turonian), Paleoceanography, 17, doi: 10.1029/2002PA000778. pdf



Orbital Parameters (in prep.)

How does the model respond when Earth's orbital precession, obliquity and eccentricity are varied?
How do the model results help us understand cyclicity observed in Paleogene and late Cretaceous marine sediments?

Experiments describing the precipitation d18O sensitivity to orbital changes are not yet published, but you can view previous, related sensitivity test results described by:
Bice, K. L., and R. D. Norris (2003), Model simulations of orbitally forced terrestrial and surface ocean variability in the Paleogene greenhouse climate, Eos Trans. AGU, 84 Fall Meet. Suppl., Abstract PP41C-0848.

view ABSTRACT
view POSTER  (22 MB pdf)

access links to proposal-related FIGURES



Surface Ocean Isotopic Composition (in prep.)

In uncoupled model experiments designed to simulate the isotopic composition of precipitation, how sensitive is the model prediction to the specified surface ocean composition?
What impact do uncertainties in our estimates of past ocean d18O have on model predictions of past freshwater d18O?

Full experiments describing the precipitation d18O sensitivity to specified ocean isotopic composition are not yet published, but you can view some sensitivity test results shown by:
Bice, K., D.Pollard, K. MacLeod, and B. Huber (2006) Isotope modeling of a mid-Turonian warming event in the South Atlantic, Eos Trans. AGU, 87 (52) Fall Meet. Suppl., Abstract PP23A-1739.

view ABSTRACT

view POSTER (1.4 Mb pdf)



 

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Last updated December 27, 2006
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