There are fresh fears that Europe's biggest glacier is melting fast, and could disappear within 100 years.
Vatnajokull in Iceland covers 8,000 square kilometres, and at its deepest point is more than 900 metres thick.
But experts say it's melting at a rate of a metre a year, because of rising temperatures and reduced snow fall.
They've warned that all of the country's glaciers are melting, and that rising sea levels could cause bad floods in other parts of the world.
Scientists say people living in low-lying areas might have to move to higher ground to escape the rising waters.
In the short term, there may be some benefits for Iceland, because warmer temperatures mean farmers can grow things for longer.
But environmental campaigners say the long term effects are really worrying, and are calling for more to be done to stop climate change.