1. We're planning to destroy Earth, not save it.
2. There are lot's of greenhouse gasses needed(Like, a lot.) We can't transport anything without creating more greenhouse gasses to move it.** Instead I propose we melt Mars ice layers, thereby hitting 3 birds with one stone:
A: Liquid water
B: Greenhouse gasses (That are captured in the ice)
C: We get to blow up a large area of our own planet
3. A space elevator, by it's very idea needs to be constructed at the equator. Also, it can't be build in the timeframe of the mission*. (Also, don't want to give Earth an advantage) For going to space, I suggest using conventionall rockets, assisted by chemical drives to get out of LEO to Geo where they will be picked up by the orbiter.
*Cost way to much. To build it we would need to invest more than for the rest of the mission. Also the tech doesn't exist yet.
** Because we're talking about thousands of tonnes of greenhouse gasses, and probably even much more. (also, you can't just pluck greenhouse gasses out of the sky.)
actually if we settle on the mars equator , it is 30°temperature points there . and i am find with that .
It's never 30 degrees on the equator. In the hottest day on Mars, in the middle of Summer, it might be 20 degrees max at midday. The average temperature will always be -50 degrees or something. I hate it when people see max temperature 30 degrees and think that it's always that hot at the equator. That's an extreme, and temperatures on Mars are way more unstable then on Earth