A child dressed as a cat takes part in the Children's Halloween day parade at Washington Square Park in the Manhattan borough of New York October 31, 2015. (Photo by Carlo Allegri/Reuters)

A dog dressed in a costume takes part in the Pet's Halloween Day parade at El Olivar Park in San Isidro, Lima, October 31, 2015. (Photo by Mariana Bazo/Reuters)

Two novice Buddhist monks walk alongside a basket seller to collect alms following a clerics rule of no footwear nor use of umbrellas in Mandalay, Myanmar, Friday, October 9, 2015. (Photo by Hkun Lat/AP Photo)

A general view shows smoke and volcanic ashes billowing from volcano Cotopaxi in Pedregal, Ecuador, late 07 October 2015. (Photo by Jose Jacome/EPA)

Palestinian girls take part in a ballet dancing course, run by the Al-Qattan Center for Children, in Gaza City November 25, 2015. (Photo by Suhaib Salem/Reuters)

Artist Kong Ning wears a wedding dress made from respirators to highlight concerns about air quality and pollution in Beijing, China on December 1, 2015. (Photo by Luo Xiaoguang/Xinhua Press/Corbis)

People take part in the "Bison Race" winter extreme run competition in Zhodino, Belarus, December 5, 2015. (Photo by Vasily Fedosenko/Reuters)

Participants run through the streets of the Back Bay during the 16th annual Santa Speedo Run in Boston, Massachusetts, December 12, 2015. (Photo by Brian Snyder/Reuters)