Hawking: Solve climate change with space travel!

After publically heaping scorn on Steven Hayward of AEI for repeating a suggestion by engineers that global warming could be ameliorated by putting mirrors in space to reduce incoming radiation, he asked me:

May I assume your scorn for my mention of the idea applies equally to Marty Hoffert and the other authors of the Science piece?

To which I responded, "yes":

I am constantly amazed at scientists who don't give proper attention to even the most cursory analysis of the implications of their suggestions, if only on the back of an envelope. It took me 20 minutes to do my calculation ... . I've been in plenty of meetings where people will brainstorm fanciful ideas on the off-chance that something makes sense, but we don't publish the proceedings of those meetings in Science.

Last week, Stephen Hawking (yes, that one) added his name to my "scorn" list by suggesting that the human race needs to [emphasis mine]:

... spread out into space for the survival of the species. ... Life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global warming, nuclear war, a genetically engineered virus or other dangers we have not yet thought of.

I have never understood this argument. Cost aside -- and Hawking makes no quoted estimate of that -- if we can't handle those threats over a century time scale, what makes him think that we could put a significant human population on another planet?

Much of what Paul Ehrlich's Population Bomb predicted has not come to pass, but Ehrlich was axiomatically correct when he said that there's no a priori reason to believe another planet (i.e., more space) would help us solve our social and environmental crises, nor is there any reason to reason to believe those problems wouldn't follow us if we left.

So why does Hawking say stuff like this? Naivete? Possibly. A desire to sell the children's book he's writing with his daughter? Could be.

Honestly, I just don't get it. This is the only planet we have, and pie-in-the-sky schemes that rely on leaving are insane.

[Image from British Council]