A quarter of a million children could die next year due to the effects of climate change, Save the Children warned.
The charity said the figure could rise to more than 400,000 per year by 2030.
Its report Feeling the Heat, which is launched, claims that climate change is the biggest global health threat to children in the 21st century.
The charity predicts that 175 million children a year - equivalent to almost three times the population of Great Britain - will suffer the consequences of natural disasters like cyclones, droughts and floods by 2030.
It warns that more than 900 million children in the next generation will be affected by water shortages and 160 million more children will be at risk of catching malaria - one of the biggest killers of children under five - as it spreads to new parts of the world.
Save the Children is urging world leaders to put children first during climate change negotiations in Barcelona this week, ahead of the Copenhagen summit in December.
Ultravox star Midge Ure, a Save the Children ambassador, recently returned to Ethiopia 25 years after the 1984 famine which prompted him to create Band Aid with Bob Geldof.
"Climate change is no longer a distant, futuristic scenario, but an immediate threat," he said.
"We've all heard about the East African food crisis but I've been in Ethiopia seeing first hand the impact it's having on children's lives.
"I've seen how vulnerable children are to the effects of climate change."
