Scots have a last chance to change the world, with next month's election giving them the opportunity to influence policy before the tipping point is reached on global warming, Greens claimed yesterday.

Campaign director Mark Ruskell said a vote for the Scottish Greens should be for "progress not protest". He said the only "red line" issue that would prevent them from even discussing possible deals with other parties was new nuclear power stations.

On other issues, he said they would seek to drive a hard bargain, whether as formal coalition partners in government, or as part of a more limited "confidence and supply" deal to allow a bigger party to form a stable minority administration.

But while the Greens will feel the tide is with them in terms of sentiment about global warming and the need to curb carbon emissions, some of their mechanisms for achieving this could dent their hopes across the country.

They would oppose the building of a new Forth road bridge if it amounted to an additional crossing, and retain Forth and Tay bridge tolls, as well as introducing more "smart" charges as part of congestion charging regimes across the main cities. They want to scrap the M74 extension in Glasgow and the Aberdeen ring road in favour of cross-rail schemes.

Elements of their equality and diversity agenda - being "bold in challenging homophobia" - and their call for "integration of state-funded religious schools into non-denomination education" are bound to raise the ire of the Catholic church.

The Greens oppose the way young people have been "demonised" using anti-social behaviour powers and are robustly on the side of civil liberties and asylum seekers.

There was a lack of hard financial numbers in their 26-page manifesto, released yesterday, and those at the launch offered only a few specifics, contrasting cross-rail schemes favourably with major road projects, and claiming that every £1 spent on youth welfare would save £17 on anti-social behaviour.

The Greens' main target is "stopping the supertanker" - tackling energy and climate change. Mr Ruskell said: "We are the party that makes a serious effort to identify the root causes of Scotland's social and environmental problems.

"If the next executive doesn't take the hard choices needed to tackle climate change then it'll be 2011 before we can vote them out of office. Yet the science of climate change is telling us we must make these choices within the next four years. The current generation of voters and politicians are the last generation that can truly take action to tackle this crisis."

In addition to picking up MSPs in the central and west regions, the party hopes a split in the socialist vote in Glasgow between the SSP and Solidarity could let the Greens pick up a seat. "We're confident we will get 10 seats," Mr Ruskell said.

Shiona Baird, the Greens' co-convener, said: "If you have voted Green in the past, there could be no more important time to do so again. If you are voting for the first time, or considering voting Green for the first time, I urge you to back our vision for a socially just and internationally responsible Scotland."

Her co-convener, Robin Harper, added: "Unless more Green MSPs are elected in a month's time, the Scottish Executive and the Scottish Parliament will continue to drift on the issues that matter to the country."

Party priorities

Justice

Improve victim-offender mediation. Defend civil liberties, oppose ID cards.

Economy

Support local businesses, regulate supermarkets, introduce pollution taxes.

Transport

Re-nationalise rail, charge for congestion, shift freight off roads. Scrap M74 extension and Aberdeen ring road.

Education

Support comprehensive education, and maximum primary classes of 20. Scrap graduate endowment.

Families and Communities

Integrate children's service as part of a 10-year strategy.

Energy

Create a minister for sustainable development. Legal targets to reduce carbon emissions by 90% by 2050.

Health

Support founding principles of NHS and rejection of PFI. Up nursing bursary to £10,000.

Government

Rejection of Trident. Back a referendum on independence. Support the right to vote at 16.