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| AMS Conceptual Climate Energy Model | |
About the Model:
Earth�s climate system is driven by energy from the Sun. Climate is the story of solar energy intercepted by Earth being absorbed, scattered, reflected, stored, transformed, put to work, and eventually emitted back to space as infrared (heat) radiation. The radiant energy flowing from space to Earth and from Earth to space determines whether or not Earth is in a steady-state condition, cooling, or warming. Lack of a radiant energy balance between Earth and space creates a net loss or gain of energy in Earth�s climate system, which results in global climate change. Global climate change occurs as the climate system adjusts towards radiative equilibrium with space.
The International Panel on Climate Change (in its AR4 WQG1 FAQ 1.1 document) states, "There are three fundamental ways to change the radiation balance of the Earth:
Climate, in turn, responds directly to such changes, as well as indirectly, through a variety of feedback mechanisms."
The American Meteorological Society�s Conceptual Climate Energy Model (AMS CCEM) is a computer simulation designed to enable you to track the paths that units of energy might follow as they enter, move through, and exit an imaginary planetary climate system. The AMS CCEM explores basic concepts underlying a planet�s perpetual drive towards attaining and maintaining radiative equilibrium with space. These same fundamental physical concepts underlie the workings of Earth�s global climate system. The AMS CCEMAMS CCEM is driven by the periodic input of energy units reaching a planetary surface. These energy units may be stored, emitted, or absorbed in the planet�s climate system, which is composed of the planet�s surface and any existing atmosphere. The AMS CCEM allows user-selected choices (model settings) to display these energy interactions and provides a statistical summary of the results of each simulation �run�.
The AMS CCEM operates according to the following rules-of-play involving energy units:
Rule 1: During each cycle of play, any energy unit at the planet�s surface has an equal chance of staying at the planet�s surface or moving upward.
Rule 2: During each cycle, any energy unit in the atmosphere will have an equal chance of moving downward or upward.
The second rule is based on the physical reality that atmospheric �greenhouse� gas molecules that have absorbed infrared radiation will subsequently radiate the absorbed energy randomly in all directions. Half of the emissions will exhibit a downward component and half an upward component. In AMS CCEM, Atmospheric CO2 represents greenhouse gas concentrations of None, Current (1x), and Future (2x) as shown with 0, 1, and 2 atmospheric layers respectively.
After Model settings are selected for Atmospheric CO2, Sun�s Energy, Albedo, Initial Energy, Cycles, and Mode, the simulation is run. Random numbers are employed to assure that energy-unit movements are determined purely by chance. The Introductory mode always produces the same results for an individual simulation as all energy unit movements are determined by the same set of random numbers �frozen� for the purpose of demonstrating how the model works. In the Random mode, a unique sequence of random numbers is generated with every simulation, so no two runs with the same model settings can be exactly alike.
A Sample Run:
To gain familiarity with the model, observe several trials of the following simulation: One atmosphere / Energy: 100% / Albedo: 0% / Initial Energy: 1 unit / 20 cycles / Introductory mode. Click Run to activate. The simulation can be stopped by clicking on Pause at the top right to observe energy unit positions. Continue the simulation by clicking on Resume.
As a simulation progresses, the number of units in the planetary climate system at the end of each cycle is displayed on a graph below the climate system image. For simulations of 100 cycles or more, the mean number of units and standard deviation of cycle units over the simulation run appear above the graph. That mean and standard deviation is calculated for the cycles beyond the first 50. This eliminates any �spin up� effects of the arbitrary initial energy units conditions.
What Can You Investigate?
The AMS CCEM may be used to explore such questions as:
Answering such questions by varying the simulations run can allow you to investigation the basic issues: what is climate, and what is climate variability.
Testing for Climate Change:
To investigation the issue of climate change, one may use the CCEM Test webpage. To definitively determine whether climate change has occurred, one needs to have two characterizations of the climate system. This typically comes from the traditional descriptive view of climate as the average of weather. Thereby 30 years of weather conditions are averaged to create the �climate� state. The inherent variability of weather is included in this process by its statistical character. Then one can use statistics to further compare the statistical distributions of each climate state.
The AMS CCEM has parameters that are boundary conditions for developing each climate state. Solar energy, albedo of surface reflectance and clouds, and composition of atmospheric radiative gases all are critical factors in bounding the climate system. The test webpage allows you to compare two sets of these conditions where one quantity varies to determine if they are indeed different in a statistically significant sense. The Test panel is shown below.
Using the properties from the CCEM page, two sets of parameters are initiated. One value can be chosen as different to conduct multiple runs of each set of conditions. The means and standard deviations of those two sets of runs are then compared using a t-test for checking if there is a significant difference at specified levels.