There's plenty of people willing to stick up for dead dogs in umus o' />

It's time someone stood up for CO2. This humble little gas needs a champion.

There's plenty of people willing to stick up for dead dogs in umus or dead galahs in aviaries (and so they damn well should!). And there's heaps of folk happy to defend any beneficiary lucky enough to gross a grand a week (where can the rest of us apply?) but no one, it seems, is willing to stand as CO2's advocate.

If it was a gay gas hoping to adopt, there would be benchfuls of judges saying, "Why not?" If it was an ethnic gas, seeking a seat at the Super City table, there'd be coalitions of politicians saying, "Good on you, CO2!"

But it isn't a gay gas and it isn't an ethnic gas. It's just a quiet, decent, hard-working, invisible part of our nurturing atmospheric mantle, as essential to the ocean of air as salt is to the sea. And nobody likes it any more.

Especially actors. They hate CO2. Or, more precisely, the amount we are emitting. All of a sudden, and for no apparent reason, this modest amalgam of molecules has become the bete noire of the movie world.

Which is why we've got so many sincere and dedicated cinemactivists doing so much emoting about our emitting.

And it's good emoting, let's be fair. You'd expect nothing less from thespians. Emoting is what they do best. When someone as gorgeous as Keisha Castle-Hughes or Lucy Lawless (aka Greena, The Worrier Princess) stands in front of a screen full of raging hurricanes and belching chimneys and tells us, "There is no Planet B", most of us would happily chop off our leg to reduce our carbon footprint. (In that context, we must hope the intrepid Captain Key and his merry men have travelled to Sydney in a hot-air balloon so that they can minimise theirs.)

Mercifully, no sooner have such amputational impulses stirred within our anxious bosoms than a second and saner thought occurs. We realise these new-age evangelists, so eager to give us a green piece of their mind and so happy to feel they're playing a part in something real rather than another work of fiction, are basically just the Puritans of our age. Pretty Puritans, it must be said, whose vivacity masks their vacuity, but Puritans nonetheless.

For some inexplicable reason, human beings have always needed to feel guilty about something. Every epoch has its angsts and apprehensions, its sins and its shames. The Caped Keishaders are merely articulating ours.

And good luck to them. Turning up in a rickshaw for the premiere of The Age of Stupid is probably much more fun than shooting a nude scene for some $100 million dollar Quentin Tarantino splatter flick - even if the eco-movie's title does describe our credulity as precisely as it articulates Keisha's concerns.

Our carbon emissions aren't sinful and shameful and wasteful and wicked. Or certainly not as sinful and shameful as Greenpeace would have us believe.

A little less emoting and a little more emitting could be a jolly good thing right now. As could a little less theatrical melodrama and a little more scientific rationality.

Which, as luck would have it, we actually got last week. Not that it received the attention given to Keisha and Greena and their cast of thousands. Although that's not unduly surprising either. Those who challenge today's religious orthodoxies generally get as much coverage Galileo enjoyed in the Vatican Gazette when he was pedalling his heresies.

But at least we got a paragraph here and there reporting the rational recommendations of some renegade Australian scientists.

These radical rotters told Kevin Rudd he shouldn't worry too much about CO2. In fact, they said, he should actually be quite grateful there'd been a bit more of it about in recent decades.

Because that increase in gaseous volumes had played no small part in allowing farmers to produce the much larger amounts of food needed to feed all the millions of extra people on Planet A.

(Many of whom had managed to stick around because of all that extra food produced, in part, by all that extra CO2.)

And while this stunning revelation may shock and amaze your average actor, it will come as no surprise to anyone with a decent sense of humus. Such folk are well aware that CO2 is the compost of the clouds, the fertiliser of the sky.

They know this endearing little emission helps make our gardens grow. And always has. Sixty-five million years ago (just before that damned asteroid arrived), the world was a much, much greener place. There were plants everywhere. Plants for Africa. Plants in Africa - and at the South Pole, too. That's why there were so many 70-tonne diplodocus' and brachiosaurs wandering about.

So three cheers for the compost of the clouds, my friends. Let's celebrate this invisible agent of growth. Forswear the planetary Puritans. Curse not CO2. Emit more, not less - because every green piece needs it!