The issue is thought to be a winner for McCain as the campaign moves to attract independents and siphon off younger voters from Barack Obama.
McCain is careful in the ad though to make clear that he does not think "high taxes and crippling regulation is the solution."
Here is the transcript:
ANNOUNCER: Our environment in peril,
Oil and food prices out of control,
Climate change wreaks havoc with deadly weather.
One extreme thinks high taxes and crippling regulation is the solution.
Another denies the problem even exists.
There's a better way.
JOHN MCCAIN: I believe that climate change is real.
It's not just a greenhouse gas issue.
It's a national security issue.
We have an obligation to future generations to take action and fix it.
I'm John McCain and I approve this message.