A groundprint shows what fraction of the atmosphere will be warmed 2o Celcius by a carbon emission.
The governments of the world have agreed that humans must not allow the amount of CO2 in the atmosphere to rise above a level which would cause a two degree warming. A groundprint shows you how much air rises to that concentration from a CO2 emisson. It is visualised as an area of the Earth’s surface, and refers to the amount of air above that area, in a column all the way up to space.
For example, it is estimated that about 30 years of our current emissions would warm all of the air in the atmosphere by two degrees. So one year’s emissions would warm about 1/30th of all the atmosphere…. this 1/30th is equivalent to all the air above 1/30th of the earths surface. Thus the groundprint of one year’s global emissions (approx 30 billion tonnes CO2) is 1/30th of the earths surface.
Patience please, Pete