Professor David King, using computer predictions, said worldwide temperatures will soar more than 3 degrees Celsius(5.4 F) over the next decades, causing worldwide cereal crops to drop up to 400 million tons.
King's government report said a 3 degree Celsius rise would also create water stress among 1.2 billion to 3 billion people. The report said few ecosystems can adapt, while a fifth of coastal wetlands would be lost, reports the BBC.
Britain's Prime Minster Tony Blair has called for a global consensus on stabilizing greenhouse gas emissions, but the United States has refused to cut them, the report said.
King told the BBC: "What we are talking about here is something that will play through over decades -- we are talking 100 years or so. We need to begin that process of investment."