A woman wears a face mask in the part of the city near neighbourhoods known for burning coal for heating in Ulaanbaatar, Mongolia January 26, 2017. Not many people in Ulaanbaatar wear masks to protect themselves against pollution. (Photo by B. Rentsendorj/Reuters)

A supercell thunderstorm develops, May 8, 2017 in Elbert County outside of Limon, Colorado. With funding from the National Science Foundation and other government grants, scientists and meteorologists from the Center for Severe Weather Research try to get close to supercell storms and tornadoes trying to better understand tornado structure and strength, how low-level winds affect and damage buildings, and to learn more about tornado formation and prediction. (Photo by Drew Angerer/Getty Images)

An air tanker drops fire retardant on flames as firefighters continue to battle against the Detwiler fire in Mariposa, California on July 19, 2017. The Detwiler fire is currently at 7 percent containment and has burned more than 45,000 acres and destroyed eight structures. (Photo by Josh Edelson/AFP Photo)

A bus goes through a flooded street in Wuhan, Hubei province, China July 6, 2016. (Photo by Reuters/China Daily)

The International Space Station (ISS) moves along its orbit above at the Russian leased Baikonur cosmodrome, Kazakhstan, Thursday, July 18, 2019, with a statue of Soviet Union founder Vladimir Lenin in the foreground. Circular star tracks around the Polar Star and tracks of the ISS is the result of the camera multiple exposure with a total duration of two hours. (Photo by Dmitri Lovetsky/AP Photo)

A Palestinian man takes a selfie picture next to a camel at a livestock market in the West Bank city of Hebron on August 9, 2019, as muslims prepare for the Eid al-Adha celebrations. Known as the “big” festival, Eid Al-Adha is celebrated each year by Muslims sacrificing various animals according to religious traditions, including cows, camels, goats and sheep. (Photo by Hazem Bader/AFP Photo)

The Canary Wharf financial district stands in London, Britain on August 11, 2019. (Photo by Simon Dawson/Reuters)

First Lady Melania Trump kisses Canada's Prime Minister Justin Trudeau next to the President Donald Trump during the family photo with invited guests at the G7 summit in Biarritz, France, August 25, 2019. (Photo by Carlos Barria/Reuters)