Plans to stop climate change aren't enough, and the world will get warmer by 3C, a top scientist has warned.
Research by Professor David King, who advises the government, said the increase would cause drought and famine and threaten millions of lives.
The temperature change could ruin crops and at least a billion people might not have enough water because deserts would get bigger.
The warmer weather could also destroy half the world's nature reserves.
The research also found that few ecosystems, such as natural forests, would be able to adapt to the new temperature, and a fifth of costal wetland areas would also be lost.
Plan to cut emissions
The government it trying to limit worldwide greenhouse gas emissions, which have been blamed for climate change.
But the research found these targets won't be enough to prevent global warming in the future.
Countries such as the USA have refused to cut emissions and emissions in India and China are rising.