If I was doing that, I would say, "According to the UN, if we don't change course, by the end of the century, we're likely to get about four degrees Celsius of warming."
"UN에 따르면, 세기말까지  우리가 방향을 바꾸지 않으면 기온이 섭씨 4도나 더 오를 것이다." 라고요.