With Firefox you can help fight global warming!

OK now I stumbled upon this ad-on for firefox called green. Apparently this uses the advertisement provided on websites to finance a anti-global warming campaign thingy.
And it's free.
Don't know if it's true but it sounds good enough for me.
Green is a tiny piece of software with a great big goal: Harness the power of the Internet to fight global warming.
When you install Green on your computer, it uses money from the usual ads you see on webpages to finance the development of clean energy sources like solar and wind, and to fund environmental efforts like reforestation. Earth-friendly projects like these reduce Greenhouse gases and help fight global warming.
Green is easy to install and works automatically. Once it is installed, just browse the web like you already do. There are no special webpages to visit, no special buttons to click, no annoying popup ads to contend with. As you browse the web, Green learns about your interests and places relevant ads in the spaces that are already reserved for ads on the webpages you visit. You won't see any more ads than usual. In fact, in most cases you will see fewer ads with Green installed.
We built Green because we believe you should be in control of the information you consume. Green gives you control over advertising. As far as we know, we are the first company to make it possible for you to apply webpage ad revenue to the crucial fight against global warming.
And it's free.
Don't know if it's true but it sounds good enough for me.