goddamnedfrank, thanks for proving me right frankie:

The answer is Venus via heat conduction

I was clear when I said ‘radiation’ dude. Because of Venus’ thick atmosphere very little ‘radiation’ makes it the surface. And I was clear when I said the nature of Mars means it will react more to smaller changes in radiation than Earth will (and Venus). And who is this ‘we’? Are we wikipedia? Are you a GSFC/JPL/ESA scientist?

OK, let’s get more into it my friend. You do understand poles get much lower solar flux than equators due to the angle to the Sun, so that polar regions will be more sensitive to flux changes than equators. This is why a martian ice cap can be greatly impacted by slight changes. Combine your distance with the low flux and you get a highly sensitive indicator to small changes in radiation. Small drop increase in solar output is then diffused by distance and further diffused by incident angle - therefore small change big drop in the energy input to the Martian poles.

Doh!