For one, Earth is much further away.
But most importantly, we have no clue if our current carbon levels are any sort of maxima in regards to what the planet can handle. We just have our own little recent industrialized history, and some charts about the past that are, at best, educated guesses.
As George Carlin would say, "The planet will shake us off like a bad cold"
Climate change is more important for our species survival much more so than the planet. The planet will be fine. The planet will recover after we're gone.