## Tuesday, June 20, 2006

Nanny wants to know

if the forcing by CO2 has grown since 1950 and if the rate of growth of the forcing has increased. Fortunately for him, we can find the answer in a PNAS paper by Sato and Hansen

Click for clearer/larger image

These are not the forcings, but the rate of change of the forcings. The rate of growth for CO2 forcing has clearly increased, as has the forcing itself. On the otherhand, it appears that the CFC forcing is actually decreasing (thanks to the Montreal Protocols).

The actual changes in forcings and concentrations can be found in an earlier Rabett Run posting

PS. You can also find the forcing for CO2 in the PNAS article CO2 F = f(c) f(co), where f(c) = 4.996 ln (c + 0.0005c2). co is the preindustrial value for the CO2 mixing ratio in ppm. From this and concentration data you can calculate changes in forcing and changes in the rates back to the year dot.