You're seriously underestimating the power of mankind then.
Man has influenced every other part of the environment. Leveled mountains, dammed rivers, filled the sky with smog, turned forests into farmland. There are minerals which exist on Earth now that have never existed at any other time during the Earth's history because of human activity. We can make seeds that only grow when they are sprayed with a patented chemical. We even thinned the ozone layer using nothing but refrigerators and deodorant cans.
But modifying the climate, no-sir, that's simply out of the question.
