In the last 26 million years or so, the Earth has been almost uniformly covered in ice. THe ice ages last for millions of years; the periods in between (such as we are living in now) typically last less than 250,000 years at a time. Although the jury is very much hung on the global warming issue (in fact, those old enough to remember might recall that in the 60's and 70's it was "global cooling" everyone was worried about, with all the same bullshit psuedo-science to back it up that the global warming crowd uses today) frankly, if it staves off a civilisation-ending ice age from setting in, I say heat this sucker up until I get a tan between the front door and the car. I'll get some SPF-9,000 and not worry about it, thanks.
Phaedrus