You can't just use the amount of co2 in the atmosphere to estimate the probable degree of global warming we might expect in the future. What you also need to factor in are the effects of the other greenhouse gases in the atmosphere. The other greenhouse gases in our altmosphere that we are concerned with have a Global Warming Potential (GWP) greater than co2 which is used as the standard and has a GWP of 1. According to the U.S. Environmental Protection Agency (EPA), the GWP for some other significant greenhouse gases are:

• Carbon dioxide has a GWP of 1
• Methane has a GWP of 21
• Nitrous oxide has a GWP of 310
• Halocarbons (HFC) has a GWP of 140 to 11,700
• Sulphur Hexafluoride has a GWP of 23,90

This means that a ton of methane has 21 times more ability to trap heat than co2. Thankfully there is less of it so it does not have as large effect as co2 currently does; neverthess it does have a significant effect as there is alot of methane going up into the atmosphere from various sources.

You can use the EPA greenhouse gas equivalence calculator to compute the co2e amount of greenhouses gases you are emitting.

To learn more about co2e and how it is calculated you an read this co2e clarification over at Real Climate along with 193 responses to it.

The bottom line is that it is co2e that we need to be more concerned about as it is the value that we would probably plug into our models to predict the degree of global warming to expect. There probably needs to be more general education to the public about the co2e concept, how it is calculated, and where we are at now.