There is no collection of headlines as such but the closest thing is TROVE Newspapers. This is a site of the National Library of Australia that has an enormous collection of scanned Australian newspapers. Only downside is that these are largely out of copyright and not for recent decades although some newspapers have agreed to be included up to the present day.

Hope this is helpful.

http://trove.nla.gov.au/newspaper/

Thanks, Jan!

Thanks, Kenneth! I had no idea that existed. It is an excellent resource.

Understood :) I first did the math on climate change at the Naval Postgraduate School in 1991. Fascinating, but non-intuitive and very complex.