Pope Francis greets well-wishers as he departs the Apostolic Nunciature, the Vatican's diplomatic mission in Washington, D.C. on Sept. 23, 2015.

Photographer: Cliff Owen/AP P hoto

Pope Francis greets well-wishers as he departs the Apostolic Nunciature, the Vatican's diplomatic mission in Washington, D.C. on Sept. 23, 2015.

Photographer: Cliff Owen/AP P hoto

"Viva Papa!" Pope Francis Thrills Washington in Big and Small Ways

The leader of 1.2 billion Roman Catholics kisses a baby, commutes in an environment-friendly Fiat 500L, and greets well-wishers during his tour.

In the nation's capital on Wednesday, the leader of 1.2 billion Roman Catholics kissed a baby, commuted in an environment-friendly Fiat 500L, and spoke out against climate change.

Pope Francis give the thumbs-up from the popemobile during a parade around the Ellipse near the White House in Washington, D.C.

Photographer: Carolyn Kaster/AP Photo

A selfie with a cardboard cut out of Pope Francis near the White House.

Photographer: Bill Clark/CQ Roll Call via Getty Images

People arrive for a Canonization Mass for Rev. Junipero Serra at the Basilica of the National Shrine of the Immaculate Conception in Washington, D.C.

Photographer: Brendan Smialowski/AFP via Getty Images

Pope Francis is kissed by a member of the crowd as he departs the Apostolic Nunciature, the Vatican's diplomatic mission in Washington, D.C.

Photographer: Cliff Owen/AP Photo

Pope Francis as he departs the Apostolic Nunciature, the Vatican's diplomatic mission in Washington, D.C. 

Photographer: Cliff Owen/AP P hoto

A banner of Pope Francis in Philadelphia.

Photographer: Spencer Platt/Getty Images

Pope Francis disembarks from his airplane upon arrival at Andrews Air Force Base in Maryland.

Photographer: Saul Loeb/AFP via Getty Images

Pope Francis prepares to depart in his Popemobile after leaving the cathedral where he held a mass and blessed the city in Santiago de Cuba, Cuba.

Photographer: Joe Raedle/Getty Images

President Barack Obama and Pope Francis during an arrival ceremony on the South Lawn of the White House in Washington, D.C.

Photographer: Mandel Ngan/AFP via Getty Images

Pope Francis meets Fidel Castro in Havana, Cuba.

Photographer: Alex Castro/AP Photo

A glass-framed photo of Pope Francis on display at the gift shop at the Basilica of the National Shrine of the Immaculate Conception in Washington, D.C.

Photographer: David Goldman/AP Photo

A mural of Pope Francis in New York City.

Photographer: Spencer Platt/Getty Images

Sebastien N'zau of the Democratic Republic of the Congo wears a shirt celebrating Pope Francis ahead of the Pope's scheduled visit in Philadelphia.