yes - "needed" (past tense)
From Nick's page "Climate Models for Early Mars":
There are plenty of scientific papers that have looked at Earth, or Venus, or Mars in isolation and stated that "early Mars was warm and wet" or "early Earth was not too hot for life to develop". However, most of these did not apply the same model to all the Terrestrial planets to see what happened. The same processes (clouds, greenhouse gases etc.) that are invoked to keep early Mars warm and allow flowing water, would also act on the Earth. To make early Mars like modern Earth we need about 3 times as much insulation in the atmosphere to compensate for the faint young Sun and the wider orbit. If we do the same to Earth's early atmosphere, then Earth becomes like modern Venus (hotter, in fact!)
The observational fact that Earth is not (and probably never has been) like Venus, is a very strong constraint that Mars has never been appreciably warmer than it is today. In fact, early Mars should have been a cold iceworld - hence my evocative description of "White Mars" (with apologies to Kim Stanley Robinson).
As I said, I'm no expert, but I'd read something carefully first before discounting it. As we know, Nick is reconsidering his theories in the light of the MER data, but I'd be suprised if he ended up ditching all of his 'White Mars' approach.