IT was billed as a conversation with the Climate Commission and today some big political names helped pack the Parliament House Theatrette for the chat.

In the front row were Prime Minister Julia Gillard, independent Tony Windsor, Treasurer Wayne Swan, Opposition climate change spokesman Greg Hunt, Environment Minister Tony Burke.

And right up the back of the raked seating, almost in the last row, the section where the lighting isn't as bright as elsewhere in the room, sat Malcolm Turnbull.

This was no stealth operation. He broadcast on Twitter his attendance at the event, from the event: "At the Climate Commission public forum at Parliament - Greg Hunt and Julia Gillard here and many other mps.''

By my count, they were the only two Opposition MPs there.

The MP for Wentworth even sent around a picture of the speakers, apologising for the quality of his iPhone camera. And he smiled as if at a private joke as news photographers took his picture.

Mr Turnbull is the Opposition spokesman on communications who also has strong views on global warming. He was a silent observer of the conversation but the optics of his presence said almost as much as words could provide.

He quite clearly was not shirking from his commitment to the science of human-induced global warming, nor from his belief that urgent action, including installing a price on carbon, was needed.

Both principles were endorsed by the Climate Commission in its report released yesterday.

Opposition Leader Tony Abbott has welcomed the report as support for his Direct Action plan to reduce carbon emissions by using taxpayer money to pay industries to get clean.

But there is a significant difference between Mr Abbott and Mr Turnbull on the issue, and the latter's presence at the event today underlined that.

Almost as much as Mr Turnbull's appearance on a TV program last week in which he essentially laid out the flaws of Direct Action, including its considerable cost to taxpayers.

He asked a question of the expert panel, but after the event referred reporters’ questions to Mr Hunt.

But even if he had been a mute observer today, Mr Turnbull paradoxically would have showed he was not going to be silenced on the climate change issue.