@Herald,
Since you can't use a simple online calculator to admit that you are wrong then let's use Excel to graph the CO2 and add trend lines.
You can download the data in an excel spreadsheet here:
http://co2now.org/images/stories/data/co2-mlo-monthly-noaa-esrl.xls
Now one can take the data, chart it and add trend lines.
Highlight a column of data for any month. Go to Insert, line chart, 3d chart
Go to Layout, Trendline, Linear
Then go to Layout Trendline, Exponential
You will find that the linear trend is almost exactly the same as the exponential trend. That points to the increase being closer to a linear increase over time than an exponential one.
Anyone can do this. I urge anyone that questions which of us is correct to do it. I urge you to do it and come back and tell us the results and how you interpret them.
To make this even more interesting, let's graph the 3 year moving average.
select the data you want to create the moving average for. Click Data, Data Analysis. (You may have to install the free Analysis Tool Pack if you don't see it.) Select moving average. Select data input, set interval to 3, select an output cell. Click OK.
Now you can graph the 3 year moving average. Add the linear and exponential trend lines. Surprise. (or not). It looks exactly like the data without averaging.