Note again I'm not saying this effect accounts for ALL or even MOST of the warming on earth.
What effect? Some observations seem to show that the Martian icecaps are shrinking. No cause has yet been found. We know it's not the sun -- there has been no increase in solar output.
[the "effect"] seems to account for between 15%-60% of [warming on earth], probably close to 30%.
Where do you get these figures?
If there is some mysterious "effect" that is causing (part of) the warming on earth there must be an equal and opposite unknown effect that is causing cooling, too, otherwise there would be no match between the observed warming and the known cause for that warming (CO2 increase).