单项选择题

（B） Is there link between humans and climate change or not This question was first studied in the early 1900s. Since then, many scientists have thought that our actions do make a difference. In 1997, the Kyoto Protocol explained our role in the Earth’s changing atmosphere and set international limits for gas emissions(排放) from 2008 to 2012. Some countries have decided to continue these reductions until 2020. More recently, the Paris Agreement, stuck by nearly 200 countries, also aims to limit global warming. But just now how much warmer it will get depends on how deeply countries cut carbon emissions.
If those island nations not far above sea level are to survive, the maximum temperature rise, since the start of the industrial age, should be_______.