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Scientific Process
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Sequence of Events
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Government & Press
Reports
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Observation of physical phenomenon / identification of
key and unimportant variables (e.g., temperature, CO2, water
vapor in atmosphere, number of rabbits in Australia).
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- Observe ~1 degree F (some say 2) increase in global
average, atmospheric (at Earth surface) temperature
during the past 100+ years.
- Observe (exponentially?) increasing concentration of
atmospheric CO2 at Mauna Loa observatory in Hawaii during
the past ??? years.
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From the EPA:
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Formulate working hypotheses (which imply realizable
"models" for the Earth's climatalogical system).
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- Easy hypothesis-- Earth is warming up.
- Harder hypothesis-- Earth is warming up because of
human activity.
- Hardest hypothesis-- Earth is warming up because of
human activity. Corrective action should be taken.
Scrutinize various hypotheses. For example, how does
observation 1 relate to observation 2?
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Refine and embellish hypotheses.
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Develop the simple "greenhouse gas" conceptual model.
- Sun is much hotter than Earth, hence is transferring
energy to the Earth via radiative processes.
- Broad-spectrum radiation is absorbed by the Earth.
Some of it is radiated back into the atmosphere at
different wavelengths (e.g., absorbed as light, radiated
as infrared ("heat").
- CO2 and other "greenhouse gasses" (methane, water
vapor) absorb infrared energy that would otherwise escape
into space. They then radiate absorbed energy back into
the atmosphere (in all directions).
The simple model can be further refined by "adding" the
effect of oceans, polar climates, cloud cover, etc. This is
much harder than it sounds.
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Hypotheses testing (in lieu of direct experimentation,
which is difficult to undertake on a global scale). This
inevitably leads to more hypothesis refinement and further
testing.
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Build a computer simulation (sometimes called a model
just to confuse matters) that includes approximations to the
processes included in the simple greenhouse gas model. This
involves several steps which must be constantly reanalyzed:
- Examination of variables
- complete list?
- unknown interactions (feedback loops) and
governing equations?
- how well do we know our observations?
- Break zone to be simulated (e.g., atmosphere, land
surface and oceans) into cells, "small" volumes
over which physical properties can may vary in unknown
ways. The interaction between cells is prescribed by
equations approximating the physical processes e.g., an
equation that the concentration of CO2 to the amount of
infrared energy escaping into space
- Given that the smaller the cells, the better the
results, get the largest, fastest computer available.
- Address completeness and accuracy of model issues.
Have we included all important processes and will the
simulated results make sense?
- Compare simulation results (really, predictions) to
observations, recognizing that both have some degree of
uncertainty associated with them.
Further refine the model by adding simulation of
previously unidentified important processes, use smaller
cells, better approximations to governing equations, etc.
Bottom line, we trust a particular computer simulation
according to how well it "predicts" the observed Earth
climate during the past few decades.
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Result of study
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The final product-- a believable computer simulation
providing:
- substantially complete explanation for climate
observations
- identification and understanding of all important
processes/feedback mechanisms
- trustworthy future climate predictions
- ideas about how to effectively undertake corrective
action (and whether it is truly needed!).
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