Louise McKenchnie, 20, and Ana Heyatawin, 58, were jailed for three months each.
Dr Ben Buse, 36; Roman Paluch, 28; Oliver Roc, 41; Emma Smart, 44; Tim Speers, 36; and James Thomas, 47, were jailed for four months each.
Ben Taylor, 27, who told the court he would continue to block roads if freed, was jailed for six months.
After the sentencing, a letter from the nine was read out on the steps of the High Court. It said: “By imprisoning us, the government shows its cowardice. They would rather lock up pensioners than insulate their homes. They would rather lock up teachers than create thousands of proper jobs.
“They would rather lock up young people than take practical steps to reduce emissions. They will lock us up and leave thousands to die of cold this winter. We knew we would face prison when we took this action, but we could not stand by while the government betrays the general public.”
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Defendants told The Big Issue on Tuesday, ahead of the hearing, that they were expecting custodial sentences.
“Yes I am nervous, anxious, terrified, excited. But it’s good to be able to explain why we’re doing this,” defendant Dr Ben Buse said.