Former Vice President Al Gore has endorsed Hillary Clinton on the opening day of the Democratic National Convention in Philadelphia.

Gore, who served with President Bill Clinton, made the announcement via Twitter.

“I’m not able to attend this year’s Democratic convention, but I will be voting for Hillary Clinton,” Gore wrote. "Given her qualifications and experience -- and given the significant challenges facing our nation and the world, including, especially, the global climate crisis, I encourage everyone else to do the same."