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 American Meteorological Society’s Conceptual Energy Model (AMS CEM) 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 CEM 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 CEM 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 CEM 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 CEM operates according to the following rules-of-play involving energy units:
The second rule is based on the physical reality that atmospheric 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.
After you select model settings for Atmospheres, Sun’s 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.
To gain familiarity with the model, observe several trials of the following simulation: One atmosphere / Energy: 100% / 10 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. Also, a five-cycle running mean is added to smooth variations and show trends. Above the graph, the final mean number of units and standard deviation of cycle units over the simulation run appear.
Notice: The AMS CEM utilizes HTML5. If you experience difficulty, you may need to update your Internet browser to the latest version. For example, you will need Internet Explorer 9 or Firefox, or Google Chrome to use the HTML5 applet.
The AMS CEM may be used to explore such questions as: