We could stop all fossil fuel burning today, and we would still need to sequester carbon.

Compared to time travel, carbon sequestration is easy tech.

And you would need nothing less than time travel in order to persuade the mining companies of the 18th-20th century not to mine coal.

If by "we" you mean everyone, no we can't.

Edit: assuming you know it's too late not to start, propose something other than magic wand obvious solutions.

Probably too late for that.