It was more than six years since Al Gore had appeared in an official capacity on Capitol Hill. In January 2001, one of his joyless final tasks as outgoing Vice-President had been to formally certify the votes of the man who had just beaten him in the battle for the White House. Yesterday, after a twisting, reflective journey of reinvention, Mr Gore returned to deliver a message not only for President George Bush, the man who defeated him, but the entire world. His topic, typically enough for Mr Gore, was the danger of climate change. Whether his appearance was also part of an as yet undeclared "ghost" campaign for next year's presidential contest remains to be seen.