Stop Global Warming, paint your roof

[muddyrocks]

http://www.oldhouseweb.com/how-to-advice/tin-roofs.shtml

Did a little more reading, apparently the "tin roof" is actually iron plated with Tin.....

Interesting...

Definitely better paint that!

Yup, even the "old timey tin" coils are primed at the factory. Snake oil?
Stainless steel is hard to work and costs more but will deliver all your expectations. Expect stainless steel to provide the best service in high wind-load and high polutant atmospheres.
And of course zinc is good too; repairable after years of neglect and patinas to a nice grey.
Don't forget copper, it can last your kids lifetime (pardon the expression) and is also servicable. It is a 'darker' material and thus retains a bit more heat but it protects itself mercilessly.