You don't make progress by hitting the brakes. A humanity that destroys earth and is forced to move into space will be more successful overall, potentially, than one that does nothing on earth because we might harm the environment. It takes seven billion minds, seven billion human beings, to come up with the minds capable of solving the ideas that need solved. You only get an einstein every few million people, and you only get great inventions from greed and need. By saying we should hold back, we restrict that capability for mankind to progress. That we look to mars as we destroy earth is not a crime, it is a great thing, and part of human nature. We never hold back, we adapt to what hits us, defeat it, and keep progressing until something new threatens us. We won't fix this earth, or learn to fix mars, without being forced to. So it's better we are than not. Even thousands of death at the hands of global warming will make up for the potential millions, if not billions, that result from mankind's reach into space. Just as the industrial revolution killed thousands in factories, inspired the efficient death camps of the Nazis, but improved the world nonetheless. To me, global warming is a sign, and a strong sign, that humanity is moving forward. We have become aware of the effects of our actions, first as nations, now as a world. And we will find a way to terraform earth, to fix what we fucked up, develop the technologies that let us do so, before we unlock the path to mars. And it makes me sad that humans fantasize about terraforming Mars when they can't even stop themselves de-terraforming Earth.