The concept of "CCN formation potential"
We have developed the concept of “CCN formation potential” to quantify how emissions of SO2 from different regions affect CCN concentrations by different amounts. We used GLOMAP to quantify CCN production from SO2 emissions from N America, Asia and Europe. The CCN formation potential is defined as the fraction (of global) CCN produced by the region divided by the fraction of SO2 emitted. The CCN formation potential varies by more than a factor 2 between these three regions. Thus, 1 kg of SO2 emitted from one region can have quite a different climate impact as 1 kg emitted from another region. This variable impact on climate adds to an effect noted previously by others, that the fraction of SO2 converted to sulphate varies between regions.
The reason for the regionally variable CCN formation potential lies in the different CCN formation pathways. For example, Asian SO2 emissions are lofted high into the free troposphere where the resulting sulphuric acid vapour readily forms new particles by nucleation.
Read the paper online here