Okay let's Melt the Polar Ice:

Today we will run a simulator under many conditions to assess the sensitivity of global warming predictions to climate model parameters, population growth, and continued world economic development. You will then publish your various model parameters to frame the discussion. The simulator has many different things to adjust and we can literally run hundreds of models (Beware the wicked witch ...)

Tools:

Explanation of Simulation and Simulator Parameters:

We begin in the year 1900 with initial CO2 of 280 ppm, initial world population of 1.5 billion, and initial CH4 concentration of 20 ppm in equivalent CO2 units (we assume the global warming potential of one methane molecule to be 21 times that of one carbon dioxide molecule). This standard scenario will correctly reproduce the observations at the year 2000. From there we extrapolate to the future.

Our goal is to adjust various parameters, under various assumptions, to determine which models melt the world's polar caps and which don't. We will then discuss the reality of our assumptions based on the model results.

Each time step of the model is 30 years and is activated by the "Take One Step Forward" button. You can read the data points off of any of the curve by mouseover on that curve.

Adjustable Parameters:

  • Pop = annual world population growth (in general you will not adjust this)

  • Capacity = This is the carrying capacity of the Earth in units of billions or people. The default is set to 1000 - while completely unrealistic, this allows the business as usual exponential growth scenario to continue. For this exercise, don't change from the default value.

  • CO2 = In this simulation, this factor is treated as a percentage of the total worlds population that uses Fossil Fuels. For the 20th century, an average of 1/6 of the worlds population using Fossil Fuels combined with an average population growth rate of 1.5% correctly yields both the world's population and the measured CO2 concentration in the year 2000.

  • CO2V = This is the time, in years, it would take for the current fraction of the worlds population (set at 1/6 by default) to double its use of fossil fuels. For example, the default is +20 meaning that in 20 years 1/3 of the world's population will be using Fossil Fuels. If you set it to 40 years then it would take 40 years for 1/3 of the world's population. So carbon reduction intensities are coded into this. The bigger the number, the lower the carbon intensity.

    Note that mechanically, we can shut off the CO2 channel my making the value for CO2V to be negative

  • Anthro = This is the anthropogenic methane factor. In general it will remain at 1. However, if we can find ways to grow rice without producing methane, have co-energy generation at sewage treatment plants, eat less beef, etc, etc, you can set this factor less than 1. On the reverse side, remember the release of frozen methane and/or gas hydrates as a positive feedback mechanism. In this case, anthro will be greater than 1. In this simulation we have maxed it out at 3.

  • Lag = The time it will take for the atmosphere to initially respond in terms of having a temperature change with respect to CO2 buildup. Climatologists have no clue what this lag time might be. Empirical evidence suggests it could be as high as 75 years. In any event, this is a free parameter which can be adjusted from 1 to 200 years. Obviously the longer it is, the more favorable the climate model will be.

  • Temp = This parameter controls the relation between CO2 increase and the raise in the average temperature of the Earth. We have no idea what this parameter is. A default value of 2 is used. Values less than 2 could be considered as favorable climate models while values greater than 2 are less favorable models which are more conducive for rapid and early melting of the polar caps. We will see that our melting times are quite sensitive to the choice of this parameter.

  • Polar = This is the temperature threshold which melts the polar caps. Obviously we have no idea what it is. The parameter can be varied from 2 to 8 degrees.

  • Melting = A green vertical line will appear when the Wicked Witch chimes in. This is the year at which the polar threshold was exceeded.

After you run a model and product a result, simply click on the publish to global view button. We can then compare results on a model by model basis.