An employee of the National Park Service takes a selfie with President Barack Obama, left, in the background meeting with the crowd after a tour of Everglades National Park on Earth Day, Wednesday, April 22, 2015, in Florida. Obama used the visit to warn of the damage that climate change is already inflicting on the nation's environmental treasures. (Photo by Lynne Sladky/AP Photo)

Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

2016 Rio Olympics, Weightlifting, Final, Women's 69kg, Riocentro, Pavilion 2, Rio de Janeiro, Brazil on August 10, 2016. Leidy Solis (COL) of Colombia competes. (Photo by Stoyan Nenov/Reuters)

A dog named Yoda looks on during the 23rd Annual World's Ugliest Dog Contest at the Sonoma-Marin County Fair on June 24, 2011 in Petaluma, California. Yoda won the $1,000 top prize as the world's ugliest dog. (Photo by Justin Sullivan/Getty Images)

A boy sits on his father's shoulders to look at strawberries at the 7th International Strawberry Symposium on February 18, 2012 in Beijing, China. (Photo by Lintao Zhang/Getty Images)

Brazilians celebrate at the annual New Year's Eve beach party on December 31, 2011 for the Copacabana Reveillon in Rio De Janeiro, Brazil. (Photo by Konrad Fiedler/Getty Images)

An installation with a copy of a tank is seen at a villager's house in the village of Vits, Belarus November 8, 2016. (Photo by Vasily Fedosenko/Reuters)

Performers eat their lunch before the start of the New Year's Day Parade in London, January 1, 2016. (Photo by Kevin Coombs/Reuters)