Mark Cheney in Big Think:
Richard Dawkins, the most famous atheist in the world, created a stir when he recently declared that he was not an atheist after all, but an agnostic. The news, which came during a debate with the Archbishop of Canterbury last month, seemed at first to be a big get for God. However, in The God Delusion Dawkins was frank about his agnosticism.
So, how does Dawkins square his public persona with his lack of certitude? Easily. No matter how strongly Dawkins is associated with atheism, he is first and foremost a scientist. Therefore, "the existence of God is a scientific hypothesis like any other," he claims.
He’s always said that he’s an agnostic atheist, meaning that he can’t know God exists, hence agnosticism, but he sees no good reason why to believe in it, hence the pragmatic atheism.