The Cop26 climate conference will be disrupted by rail strikes after members of the RMT union backed industrial action.
ScotRail workers will strike from November 1 to 12 amid a dispute over pay and conditions.
Cop26 will take place in Glasgow from October 31 to November 12 and will see global leaders, activists, campaigners and protesters descend on the city.
Large-scale transport disruption has previously been predicted during the conference, with major roads in the city closed to traffic.
RMT members on the Caledonian Sleeper service, which is run by Serco, will also strike from October 31 to November 2 and from November 11 to 13.
Sunday train services in Scotland have been crippled for months as workers protest over pay and conditions.
RMT general secretary Mick Lynch said: “Both ScotRail and the Caledonian Sleeper have had adequate time to come up with a fair pay settlement for Scotland’s rail workers in advance of Cop26.
“Instead they have kicked the can down the road and left us with no option but to put this action on today.
“We know that these strikes will close rail services in Scotland but the blame for that lies with Abellio, Serco and the political leadership at Holyrood.
“It’s time for all parties to take their rail workers seriously, get back round the table and give these staff at the front line of our green transport services the justice, respect and reward they deserve. ”
Speaking before the strike dates were announced, a ScotRail spokesman said: “We’re seeing customers gradually return to Scotland’s Railway, but the scale of the financial situation ScotRail is facing is stark.
“We have made a formal written offer to all four rail trade unions to find an agreement on pay and conditions and they are taking that offer to their executives.
“To build a more sustainable and greener railway for the future and reduce the burden on the taxpayer, we need to change.
“All of us in the railway – management, staff, trade unions, suppliers, and government – need to work together to modernise the railway so that it is fit for the future.”
Scottish First Minister Nicola Sturgeon said last week that she hoped the dispute could be resolved before Cop26.
She said: “I would strongly encourage both sides of this dispute to get back round the table and find a resolution that is in the interests of those who work in our railways.”