WASHINGTON — US President Barack Obama was sworn in for a second term in office on Sunday in a small, private ceremony in the White House's Blue Room. Chief Justice John Roberts, who leads the US Supreme Court, administered the oath of office to the president, repeating a role he took in 2009, when Obama became the first black president of the United States. Obama's swearing-in, witnessed by family, met the constitutional requirement that he take the oath on Jan. 20. He will repeat the procedure in a public ceremony in front of the US Capitol on Monday. Honoring tradition, Vice President Joe Biden was sworn in before his boss at an early morning ceremony at his official residence, before the two laid a wreath at the Tomb of the Unknowns at Arlington National Ceremony. Supreme Court Justice Sonia Sotomayor -- picked by Obama to be the first Hispanic judge to sit on the High Court in his first term -- made her own slice of history by leading Biden as he took the oath. Meanwhile, climate change was thrust to the forefront of the US political agenda recently in the wake of the devastation caused by superstorm Sandy and record high temperatures across the country. But despite Obama renewing his early promises to act, experts said political opposition would make it at least as difficult as during Obama's first, failed push to get new legislation through Congress, and said decisive measures will remain unlikely. “All the public opinion polls show a better understanding of the link between climate change and extreme weather events,” said Alden Meyer, strategy director of the Union of Concerned Scientists. But, he added, “there is still a lot to do in the Republican Party and in the business community,” to get them on board with Obama's plans for solutions, should the president launch a second offensive. Growing public concern over the global warming threat was laid out in a recent study by the Rasmussen Institute, carried out shortly before November's presidential election, but after Sandy slammed into the US Northeast. The study showed that 68 percent of US voters believed that climate change was a serious problem, compared to just 46 percent in 2009. Since being re-elected, Obama has addressed climate change several times, including pledging the week after the vote to launch a nationwide conversation to find common ground, because “we've got an obligation to future generations to do something about it.” — Agencies