WASHINGTON — Former US vice president and anti-global warming campaigner Al Gore and his wife Tipper have told friends that they will separate after four decades of marriage, an aide said Tuesday.

"I can confirm," said Kalee Kreider, of the Office of Al and Tipper Gore. "They've asked for privacy during this time, for them and their family."

Kreider confirmed that the Gores -- whose affection for each other was evident at social gatherings in Washington and during his failed 2000 White House run -- had let friends know of their plans by email.

"We are announcing today that after a great deal of thought and discussion, we have decided to separate," they said in the message, first reported by the online publication Politico.

"This is very much a mutual and mutually supportive decision that we have made together following a process of long and careful consideration. We ask for respect for our privacy and that of our family, and we do not intend to comment further," they said.

Al Gore won the Nobel peace prize in 2007 for his work on raising awareness of climate change, and an Oscar that same year for his documentary "An Inconvenient Truth" sounding the alarm over global warming.

Mary Elizabeth "Tipper" Gore is a photographer who chronicled her life as the vice president's spouse as well as Al Gore's 2000 presidential campaign.

The two met at his senior prom dance in 1965 and married in May 1970.