PPM to MR calculator

The Hadley Centre climate model HadCM3 (the UM) requires the carbon dioxide and other trace gases to be inputted as the mass mixing ratio (MR) in kg/kg. That’s:

MR =ppm(gas)/ (mol. weight(dry air)/mol. weight(gas) ) /10^6

If like me, opening excel and looking up weights is a pain you don’t need, here’s a quick calculator to convert carbon dioxide in parts per million to the mass mixing ratio, and back again. Further gases may be added if I get time/inclination/asked. (Molecular mass taken from here.)

Carbon Dioxide

Enter an amount of carbon dioxide, in ppm: Mass Mixing Ratio is:
Enter an amount of carbon dioxide in MR: Parts per million:

Methane

Enter an amount of CH4, in ppm: Mass Mixing Ratio is:
Enter an amount of CH4 in MR: Parts per million: