In this October 14, 2013 photo, ecology professor Ricardo Freitas catches a broad-snouted caiman to examine, then release back into the water channel in the affluent Recreio dos Bandeirantes suburb of Rio de Janeiro, Brazil. Caimans are like tanks, a very old species with a remarkable capacity for renovation that allows them to survive under extreme conditions where others couldn't, said Freitas, who runs the Instituto Jacare, or the Caiman Institute, which aims to protect the reptiles. (Photo by Felipe Dana/AP Photo)

Iranian mourners cover themselves with mud during Ashoura, marking the death anniversary of Imam Hussein, the grandson of Islam's Prophet Muhammad, at the city of Bijar, west of the capital Tehran, Iran, Thursday, November 14, 2013. Hussein, one of Shiite Islam's most beloved saints, was killed in a 7th century battle at Karbala, Iraq. (Photo by Ebrahim Noroozi/AP Photo)

A woman carries her child as she watches Mount Sinabung volcano spewing thick volcanic ash, as seen from Karo on July 21, 2017. Sinabung roared back to life in 2010 for the first time in 400 years, after another period of inactivity it erupted once more in 2013, and has remained highly active since. (Photo by Gatha Ginting/AFP Photo)

This undated photo provided by NOAA in May 2018 shows aurora australis near the South Pole Atmospheric Research Observatory in Antarctica. When a hole in the ozone formed over Antarctica, countries around the world in 1987 agreed to phase out several types of ozone-depleting chemicals called chlorofluorocarbons (CFCs). Production was banned, emissions fell and the hole shriveled. But according to a study released on Wednesday, May 16, 2018, scientists say since 2013, there’s more of a banned CFC going into the atmosphere. (Photo by Patrick Cullis/NOAA via AP Photo)

The disused bobsled track from the Sarajevo 1984 Winter Olympics is seen on Mount Trebevic, near Sarajevo, September 19, 2013. Abandoned and left to crumble into oblivion, most of the 1984 Winter Olympic venues in Bosnia's capital Sarajevo have been reduced to rubble by neglect as much as the 1990s conflict that tore apart the former Yugoslavia. (Photo by Dado Ruvic/Reuters)

In this Tuesday, June 23, 2015, photo, an Israeli vendor waits for clients at the southern Israeli town of Sderot, next to the Israel-Gaza border. A year after the Gaza war, the community in southern Israel, long battered by rockets from the Hamas-run territory next door, has slowly recovered and is even seeing a quiet boom. (Photo by Oded Balilty/AP Photo)

In this photo taken on Thursday, July 23, 2015 migrants enter a train to Serbia at the railway station in the southern Macedonian town of Gevgelija. The country has become a major transit route for thousands of Middle Eastern and African refugees and migrants who cross over from Greece and then continue into Serbia. (Photo by Boris Grdanoski/AP Photo)

People climb on an artificial ice-wall in Liberec, about 100 km north of Prague, Czech Republic, Saturday, January 23, 2015. The wall was prepared in a former quarry just near the centre of the city. (Photo by Radek Petrasek/CTK via AP Photo)