In the celebrity-driven world of Twitter, Al Gore is one of the few political figures troubling the top rankings

Al Gore has reached the 1 million Twitter followers mark. How this compares with winning the Nobel peace prize, being the US vice-president, or seeing An Inconvenient Truth win two Oscars, only he knows.

Yesterday afternoon Al Gore achieved another landmark in his career as a politician and environmental campaigner as he clocked up his millionth follower on Twitter.

For a few days he'd…