Nicola Sturgeon has said she may have to consider "controversial" measures to cut Scotland's greenhouse gases.

The First Minister suggested new transport regulations may be required to cut emissions - but acknowledged these may cause concern in some quarters because transport impacts on so many lives.

Speaking at First Minister's Questions, she encouraged councils to consider cutting the speed limit to 20mph where appropriate.

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The Committee on Climate Change (CCC) said this week urgent action is needed to reduce transport, housing and agriculture emissions if ambitious new targets are to be met.

Transport emissions, excluding international aviation and shipping, have remained largely unchanged from 1990, with improved vehicle efficiency offset by increased demand for travel.

The CCC said the government should use devolved powers to roll out new policies to reduce emissions from HGVs such as driver training and a shift to rail.

The committee also recommended measures to promote efficient driving and encourage uptake of electric vehicles, and called for ministers to produce an aviation strategy which is "in line with climate obligations and international civil aviation organisation agreements".

Ms Sturgeon said: "Our new climate change plan, which will be published in draft this winter, will set out our priorities and commitments for delivering emissions reductions under the 2009 Act.

"Of course, we will also work with the committee to produce a new Climate Change Bill, with proposals to be outlined in 2017."

She also underlined "the importance of us now upping our action in areas like transport, housing and agriculture".

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She added: "I think everybody, even our critics, would accept that we have seen considerable success - although there is still work to do - when it comes to electricity generation when it comes to reducing emissions.

"But we must now go into areas which may be much harder like agriculture, transport, the energy sector more generally.

"If we are serious, as we are, about not only meeting and continuing to meet our current targets, but to meet the more ambitious targets that we intend to set in the new Act, then that is what we need to do.

"I hope that when we do put forward the new proposals to achieve that we will have support from right across the chamber."

Green MSP Mark Ruskell said: "Isn't it time for some big, bold ideas?

"Would the First Minister agree that in order to cut road casualties, protect the vulnerable and make our communities healthier, low carbon places to live, we should be saying 'twenty's plenty' on all of Scotland's residential roads?"

Ms Sturgeon said: "We would certainly encourage local authorities to consider that where that is appropriate.

"Let me firstly agree with the member. We've had considerable success, it's not been easy success to achieve.

"But in the area of climate change and reducing emissions, the further we raise our ambition, the tougher it gets to take the action - and the more controversial some of the actions become.

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"That's where consensus and support around this chamber is going to be so important.

"There is no doubt that transport, partly because it impacts directly on the lives of many people, falls into that much more controversial area.

"But if we're going to continue to meet our ambitious targets, and see them stretched even further, then we're going to have to do that."