Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

Hindu devotees (not pictured) touch a child with their feet as part of a ritual to bless him during a religious procession held to mark the Gajan festival in Kolkata, India, April 13, 2018. (Photo by Rupak De Chowdhuri/Reuters)

A plane battling the Ferguson Fire passes the setting sun in unincorporated Mariposa County Calif., near Yosemite National Park on Sunday, July 15, 2018. (Photo by Noah Berger/AP Photo)

Arsenal football supporters cheering from the train carriage window as they leave Euston Station, London, on their way to Birmingham for their team's match against Aston Villa which they lost 3-5. (Photo by Douglas Miller/Topical Press Agency/Getty Images). 19th November 1932

A student from “the cliff village” in Atule'er climbs newly-constructed steel ladders after school to go home for holidays, in Liangshan Sichuan province, China, November 19, 2016. The steel ladders which replaced the unsafe vine ladders shortened the time taken for the children to go home, from three hours to two. (Photo by Reuters/Stringer)

People attend the 50th annual NYC Halloween Parade in New York City on October 31, 2023. (Photo by Caitlin Ochs/Reuters)

This November 8, 2019, photo provided by John Guillote shows a view from the main lab of the Sikuliaq in the Chukchi Sea. University of Washington scientists onboard the research vessel are studying the changes and how less sea ice will affect coastlines, which already are vulnerable to erosion because increased waves delivered by storms. More erosion would increase the chance of winter flooding in villages and danger to hunters in small boats. (Photo by John Guillote via AP Photo)

A colourful morning sunrise on Christmas Eve at Victoria Tower on Castle Hill, West Yorkshire, England on December 24, 2017. The history of human activity on the Castle Hill goes back over 4000 years. The site was developed as an iron age hill fort, surrounded by defensive ditches and ramparts. In the Middle Ages there was a castle on the hill, of which the well remains. The present tower was built to commemorate Queen Victoria's Diamond Jubilee of 1897. (Photo by Charlotte Graham/ZUMA Wire/Rex Features/Shutterstock)