SNP and Green ministers have been told to urgency explain how transport and farming emissions will be cut at a faster rate than the rest of the UK.
Chris Stark, chief executive of statutory advisers, the Climate Change Committee (CCC), told MSPs that Holyrood’s target to cut 75% of 1990 levels of carbon by 2030 is “going to be very, very challenging to meet”.
Speaking to Holyrood’s Net Zero, Energy and Transport Committee, the former Scottish Government official stressed that Scotland’s 2045 net zero target is a crucial component of the UK’s overall 2050 ambition – and not down to more political ambition north of the border.
He added: “The achievement of 2050 net zero for the UK does rest on Scotland getting there five years earlier at least.
“The reason for that isn’t because we think Scotland is in a different political position and willing to make these ambitious statements – it’s because Scotland has a greater capacity to do some of the things that we will need to see happen across the UK to get to net zero.”
Mr Stark added that the 2030 target, set stricter than the CCC had advised, “is ahead of the path that the rest of the UK will be following”.
He said: “Scotland is going to need to work really hard and in some areas it will need to be ahead of the journey the rest of the UK nations are making.”
Mr Stark told MSPs that “a crucial part of the transition which is notably absent at the moment is a routemap for agriculture”, which he claimed has “so far been quite resistant to cutting emissions”.
He added that the SNP Government has “really big commitments” to cut transport emissions, but warned “that will rest on a host of policies that we haven’t yet seen”.
He said: “That is going to need to be a much stronger focus because the challenge of cutting transport emissions faster than the rest of the UK involves doing things around walking, cycling, public transport that other parts of the UK may not be pursuing.
“A really important part of this transition is that it can’t just rest on electric vehicles.”
Earlier, the CCC’s chairman, Lord Deben, told MSPs that plans to reach net zero was “at very best, piecemeal and actually, very often non-existent”.
He added that when Glasgow hosts the COP26 global climate conference in November, “people will not actually believe that the targets we have set are real”.
He said: “They only become real if you show that you have got in place the mechanisms to achieve that.”