It's not the mega-mine promised, or feared — but, if we can believe Adani's assurances, it's nonetheless a game changer that will open a vast new coal-mining region, the last major untapped coal resource in Australia.

For eight years, Adani has cried wolf on the Carmichael coal mine, announcing on multiple occasions that finance was imminent and the mine would soon be underway.

Yet it failed to secure bank finance anywhere in the world or to gain government-backed funding from China, Korea or India.

Now, it's going it alone.

The giant conglomerate run by Indian billionaire Gautam Adani will, apparently, dig into its own pockets to 100 per cent finance a much pared-back mine and rail project.

Some are still sceptical. Julien Vincent of Market Forces, a long-time critic, describes the claim of "financial close" as "highly questionable".

But it's likely that the Indian group can fund some style of venture in North Queensland out of its own resources; it's also said to be squeezing contractors and suppliers to effectively help fund the mine.

If it does go ahead, the Carmichael mining venture initially will be very small — that's all Adani can afford to self-finance.

Eventually, Adani claims it will "ramp up" to output of 27.5 million tonnes a year — less than half the 60 million tonnes a year output which has approval.

The railway to transport the coal will be narrow gauge which greatly limits the potential capacity.

Its hoping to rely on a spur line from the mine that would join up with an existing railway owned by Aurizon, but as yet it has no agreement in place that guarantees this rail access.

Had it gone ahead at the original scale, the Carmichael mine in North Queensland's Galilee Basin would have been the biggest export coal mine in the world.

Even at 27.5 million tonnes it would be massive, but there is much room for doubt about whether it will reach this scale.

Why now?

One suspects there may be a political strategy in play in the timing of Adani's announcement.

In the debate about climate change versus coal mining, Adani has become a totemic issue.

Announcing a go ahead — even for a small, scaled-down project — could blunt the community and political campaign against the mine and reduce the likelihood of Adani's mine becoming a major focus of the coming federal election campaign.

For those concerned about climate change, and for those seeking to exploit the nation's coal reserves, the issue is that the Adani mine may just be the start.

A slew of other Galilee basin projects are in the pipeline: Alpha coal, a joint venture between Indian giant GVK and Gina Rinehart's Hancock Prospecting; the China Stone project, which could potentially loop into Adani's railway; and Clive Palmer's Alpha North coal "monster mine".

It's not clear whether these projects would be commercially viable. The quality of the coal in the Galilee Basin is low compared to the high quality, benchmark thermal coal in Australia's Hunter Valley, or the coal in Queensland's Bowen Basin.

Although the highest quality thermal coal has been rising in price, in the face of climate change concerns the price of the lesser quality coal — of the kind found in the Galilee Basin — has been falling, and recently hit a two-year low.

But if the huge resources of the Galilee are exploited many fear it could spell climate change disaster.

Proponents of the mines reckon these projects make little difference to global warming because power stations in Asia would get the coal from somewhere, and potentially from inferior quality coal resources.

The economic reality, however, is that if there is a flood of new coal onto world markets it will push down prices and encourage more coal-burning, at a time when the world's climate scientists are warning that catastrophic climate change can only be avoided if the world curbs its use of coal.