The Secret Service was forced to intervene on the eve of the G20 Summit in Hangzhou on Saturday, as a Chinese official confronted U.S. President Barack Obama's national security adviser on the tarmac. After Obama's plane landed in the eastern Chinese city, a Chinese official reportedly tried to prevent national security adviser Susan Rice from joining the motorcade, scolding her after she crossed a media rope line. It was unclear if the Chinese official had mistaken Rice for a journalist, but a Secret Service agent quickly stepped in to allow Rice through. Tensions were apparently quite high as Obama arrived to meet with world leaders, as the same Chinese official was seen shouting at a White House press aide. "This is our country. This is our airport,"the official shouted at the aide, apparently in the midst of an argument about where foreign journalists should be allowed to stand. Despite the spats, however, the U.S. and China announced that they had formally ratified the Paris climate change agreement, a move that has been hailed as a major breakthrough in the fight against global warming. “Just as I believe the Paris agreement will ultimately prove to be a turning point for our planet, I believe that history will judge today’s efforts as pivotal,” Obama said, alongside Chinese president Xi Jinping. The Paris agreement will oblige nearly 200 governments to drastically cut emissions.