In general, my software plots their data without modification. However, in some cases I wanted to compare two plots where the range (minimum and maximum values) of the two series made direct comparison too difficult. In those cases, I changed the scale and baseline of one of the plots. (This is also user controlled, but I wanted the defaults to be scaled.)
There is a basic problem when plotting many different types of data on the same graph. For instance, CO2 is measured in ppmv (parts per million by volume) and temperature is in degrees minus some arbitrary average (referred to as delta degrees). As a result, I save simply labeled the y-axis in a generic manner.
This program reads several data files (included in the zip file) and plots the data. The y-axis does not have a specific label because it is used for all the series.
The graph allows you to select between 3 different x-axes - depth, age of the ice, age of the air. The dust data is only associated with the age of the ice and, therefore, is not displayed when the data is plotted verse depth. When age of air is selected, the main change is that the CO2 data is shifted.
|CO2||This is the CO2 concentration in ppmv (parts per million by volume)|
|Delta Depth||Change in depth with respect to the quantity on the x-axis. I interpret the change in depth with respect to the change in ice age to indicate the amount of "ice" accumulation per year. The amount of snow per year is larger and eventually compacts to form ice.|
|Delta AgeIce||Change in the age of the ice with respect to the quantity on the x-axis.|
|Delta AgeAir||Change in age of the air with respect to the quantity on the x-axis.|
|Delta Air||This is the difference between the air age and the ice age.
In any given layer, the trapped air will be younger than the age of the ice.
This is because the snow allows free exchange of gases with the atmosphere
which eventually stops as the snow turns to ice.
I was surprised to see the sawtooth pattern with a minimum offset of about 2,000 years and a maximum of more than 6,500 years. There are many competing ways to compute this data, and the science is far from settled.
|Delta T||Change in temperature relative to some baseline.
Shown as the computed value scaled and offset for comparison with the CO2 and dust data.
To get the original values, use the Chart Properties dialogbox to divide the displayed value by 10 (multiply by 0.1) and subtract 25.
|Dust||Amount of dust in the ice in ppm (I assume that this is by weight).
Shown as the computed value scaled and offset for comparison
with the CO2 and temperature data.
Because the data provides only the years BP, and not the actual depth, this data is not displayed when Depth is selected. It is interesting that the amount of dust suddenly decreases as the climate warms. It is not clear if this is due to, or the cause of, the rapid change.
The common theory is that glaciers produce large deserts, and that that is the reason for the dust. Another possibility (which may be related) is that there is not enough rain to clean the atmosphere. However, there are many more theories, such as the weight of the glaciers tipping the continents (we know this happens) which might trigger volcanoes.
At any rate, the dust is highly correlated with the coldest periods and a lack of dust is correlated with increasing or stable CO2 concentrations.
To get the original values, use the Chart Properties dialogbox to divide the displayed value by 100 (multiply by 0.01) and subtract 2.
One of the surprises was that there is no CO2 data after 2,342 BP. This is one of the reasons that many people don't accept the "ice core" data as showing ... whatever. It really does not overlap with current data.