Imagine all the people in the world, what an impact.
In the blog http://www.newscientist.com/blog/environment/
You can read about a joke published in The Journal of Unlikely Science where the idea “If we merely cut out one breath in three, we could decrease the amount of CO2 entering the atmosphere each year by a staggering 0.63 gigatonnes,"
According to the “winner” of Richard Branson’s grand price of $25 million, one way of solving the problem would be having fewer humans on the planet, presumably by reducing population growth. Either that or we each need to use less energy. I think they are right in that.