SO what’s next? In just one week, Nicola Sturgeon has dumped her party’s manifesto promise to give the airline industry a £150m tax cut and put Scottish Government support for a third Heathrow runway - and related jobs in Scotland - under review.

It’s been a bracing shake-up for Holyrood, where MSPs tramping round in a constitutional rut like prisoners in a yard is usually the order of the day. When Ms Sturgeon declared a “climate emergency” at her party conference, few thought it would lead to such swift results, including perhaps Ms Sturgeon.

But now she has staked Scotland’s claim to reach zero net carbon emissions by 2045, other changes must follow. You can’t be half-hearted in an emergency.

Nicola Sturgeon: A Yes win not journey’s end for Holyrood

As Environment Secretary Roseanna Cunningham said on Wednesday, when burying the SNP’s plan to halve air departure tax (ADT), “concrete actions” must be taken. “We know that difficult decisions are required,” she said.

Let’s not get carried away, though. The SNP stumbled into its position on ADT. It didn’t go looking for it. A combination of bureaucratic delay and political pressure forced its hand. It had been ardently defending the policy until a few weeks ago, even though it knew it would generate up to 60,000 tonnes of greenhouse gas a year from extra flights.

The idea of cutting air duty was always a classic piece of corporate capture, a policy based on work commissioned by self-interested airlines themselves.

After some flattery from Easyjet and others, Alex Salmond got on board in 2011 and the idea of halving and then abolishing ADT in Scotland appeared in the 2013 White Paper on independence.

The first cut would costs taxpayers £150m a year in lost revenue, full abolition £300m. When the UK Government legislated to devolve air duty, and allow Holyrood to cut it locally, Ms Sturgeon kept the expensive wheeze alive in her manifesto.

But then red tape tripped it up. In 2001, the airports of the Highlands and Islands were granted an exemption from passenger duty to help them survive. The SNP wants to keep that exemption. But the EU has changed its state aid rules since 2001, and if the tax is devolved the exemption might fall foul of them and disappear. So after three rounds of delays, the tax remains at Westminster, where the SNP cannot cut it anyway.

READ MORE: Devolution is under attack by the Conservatives claims Mike Russell

Add to that emphatic opposition to an ADT cut from the Green MSPs the minority SNP needs to pass its budgets, plus Labour tabling a Holyrood vote to ditch the tax cut for Wednesday afternoon, and Ms Sturgeon didn’t really have much choice. The plan was effectively dead already, climate emergency or not, and she didn’t want to be seen siding with ghastly Tories to defend it. So she wrapped it in a green shroud and gave it an organic burial.

Once she’d done that, her opponents naturally moved on to the SNP’s support for the new Heathrow runway. So that joined her list of policies under review.

Note, there is no timescale for the review reporting. It’s just officials and ministers looking at things through the “new lens of climate change”.

This is a messy process, full of inconsistencies and hypocrisies. But that’s a small price to pay given what’s at stake. The SNP didn’t intend to be in this position when it made its manifesto promises or signed its memorandum of understanding with Heathow three years ago, but if its actions help save the planet, I’d recommend forgiveness.

Besides, serendipity and chance have always played a big part in politics. Sensing when the political weather is shifting and making the most of opportunities are essential arts.

And while business leaders and airport owners are squealing this week, I think the electorate will take a more enlightened view. In our hearts, we all know the world is getting sicker and worry for our children.

The new stance on the climate has also whetted the edge of a government dulled by 12 years in power. In defending policies that shorten the future, Ruth Davidson’s Tories look like dinosaurs.

The SNP’s position could secure them the support of generations of young voters, those with the most to lose, as well as foster a sense of national pride that Scotland is trying to blaze a trail. I have a hunch the SNP might be able to use the story of a county proudly re-inventing itself in another context too.

But it will not be easy. The SNP are not born-again environmentalists. They are a staunchly petrochemical party.

They wouldn’t have achieved their position without the extraction and burning of billions of barrels of North Sea oil since the 1970s - or the UK Government’s short-sighted mismanagement of a £300bn windfall. “It’s Scotland’s Oil,” went the slogan 45 years ago, and it’s still deep in the membership’s psyche. Both that sense of a wrong that must be righted, and future bounty almost within reach.

Ms Salmond was forever talking about Norway’s oil fund, you may recall.

It now stands at £750bn, thanks to decades of prudent saving, investment and state-owned oil assets. A Scottish sovereign wealth fund was dangled prominently in the White Paper.

In an interview in 2014, the then First Minister told me Scotland’s natural resources should be developed “to the fullest extent”, ie to the last drop. When I pointed out the International Energy Agency said we should leave two-thirds of fossil fuels unused to avoid cooking the plant, he said: “Well, the IEA says many interesting things, but I think we should develop.” That sentiment is not unique in the SNP.

Unspun: the political diary

The party’s Growth Commission accepted a Norway-sized piggy bank was now impossible, and recommended a more modest Fund for Future Generations. But it was still predicated on collecting billions in taxes from pumping North Sea oil and gas that would add to carbon emissions.

The idea was endorsed by the same SNP conference at which Ms Sturgeon declared her climate emergency.

She would find abandoning such a Nationalist shibboleth far, far harder than binning a mortally wounded boondoggle for the air industry.

The SNP has always been supremely pragmatic in pursuit of its founding goal - against EU and Nato membership, then for them; for the euro, then against it.

How it copes with living by principle in the face of a climate emergency will be fascinating. The moral high ground is a notoriously slippery spot.