P. Aile: Modeling Paleoclimatic Changes Using a Feedback Energetic System
123
5 DISCUSSION
From this expression of the Z transform of the solution, we can write the software
that calculates the ice volume from the astronomic signal and adjusts the model's
parameters by successive trials. The input of the model is the variations of
insolation (Berger, 1978), and the output (ice volume) is compared to the i) 18 0
sedimentary record (Raymo, et A.L. 1990). Figure 4 represents the i) 18 0 record and
the ice volume calculated by the model.
Comparison between these two figures shows that we can get reasonable results
with such a model, taking into account global mean energy balance, deep ocean
time constant, and the greenhouse effect.
6 CONCLUSION
The originality of such a model is the simple and schematic vision that allows the
introduction of parameters usually neglected in complex models, and the closedloop approach. With further development, this approach could be used to bring a
new point of view to more sophisticated models. We could test for example, the
probable mean global influence of parameters such as deep ocean and greenhouse
feedback effects, which could explain some differences between modeling and
observation (Berger et AI., 1990). This approach could help resist the temptation
to use the C02 palaeo record as an input signal (Genthon et AI., 1987; Pisias and
Shackleton, 1984), thus modeling in an open-loop way a system known to be
closed-loop.
KEYWORDS
Global change, climatic change, mathematical model, paleoclimatic evolution, C02,
i) 18 0, green house effect.
REFERENCES
[I]
Berger A., Gallee H., Fichefet T., Marsiat 1. and Tricot C., "Testing the astronomical theory
with a coupled climate ice sheet model". Palaeogeography Palaeoclimatology
Palaeoecology. 89: 125-141 (1990).
[2]
Berger A.L., "Obliquity and precession for the last 5000000 years". Astron and Astrophys
51:127-135 (1976).
[3]
Berger A.L., "Long-term variations of caloric insolation resulting from the earth's orbital
elements". Quaternary Research, 9: 139-167 (1978).
[4]
Broccoli AJ. and Manabe S., "The influence of continental ice, atmospheric CO 2 , and land
albedo on the climate of the last glacial maximum". Climate Dynamics, 1:87-99 (1987).
[5]
Gallee H., Van Ypersele J.P., Fichefet T.H., Tricot c.H. and Berger A., "Simulation of the
last glacial cycle by a coupled sectorially averaged climate - ice sheet model 1. The climate
model". Journal of Geophysical Research, 96:13139-13161 (1991).
123
5 DISCUSSION
From this expression of the Z transform of the solution, we can write the software
that calculates the ice volume from the astronomic signal and adjusts the model's
parameters by successive trials. The input of the model is the variations of
insolation (Berger, 1978), and the output (ice volume) is compared to the i) 18 0
sedimentary record (Raymo, et A.L. 1990). Figure 4 represents the i) 18 0 record and
the ice volume calculated by the model.
Comparison between these two figures shows that we can get reasonable results
with such a model, taking into account global mean energy balance, deep ocean
time constant, and the greenhouse effect.
6 CONCLUSION
The originality of such a model is the simple and schematic vision that allows the
introduction of parameters usually neglected in complex models, and the closedloop approach. With further development, this approach could be used to bring a
new point of view to more sophisticated models. We could test for example, the
probable mean global influence of parameters such as deep ocean and greenhouse
feedback effects, which could explain some differences between modeling and
observation (Berger et AI., 1990). This approach could help resist the temptation
to use the C02 palaeo record as an input signal (Genthon et AI., 1987; Pisias and
Shackleton, 1984), thus modeling in an open-loop way a system known to be
closed-loop.
KEYWORDS
Global change, climatic change, mathematical model, paleoclimatic evolution, C02,
i) 18 0, green house effect.
REFERENCES
[I]
Berger A., Gallee H., Fichefet T., Marsiat 1. and Tricot C., "Testing the astronomical theory
with a coupled climate ice sheet model". Palaeogeography Palaeoclimatology
Palaeoecology. 89: 125-141 (1990).
[2]
Berger A.L., "Obliquity and precession for the last 5000000 years". Astron and Astrophys
51:127-135 (1976).
[3]
Berger A.L., "Long-term variations of caloric insolation resulting from the earth's orbital
elements". Quaternary Research, 9: 139-167 (1978).
[4]
Broccoli AJ. and Manabe S., "The influence of continental ice, atmospheric CO 2 , and land
albedo on the climate of the last glacial maximum". Climate Dynamics, 1:87-99 (1987).
[5]
Gallee H., Van Ypersele J.P., Fichefet T.H., Tricot c.H. and Berger A., "Simulation of the
last glacial cycle by a coupled sectorially averaged climate - ice sheet model 1. The climate
model". Journal of Geophysical Research, 96:13139-13161 (1991).