A global network of ocean sanctuaries is needed to help the seas store carbon and protect nature, Greenpeace has warned.

The organisation's report - In Hot Water: The Climate Crisis And The Urgent Need For Ocean Protection - says the oceans are the Earth's largest carbon sink, trapping 50 times more than is in the atmosphere and 10 times more than that held by land-based vegetation.

It also claims human activity, such as the burning of fossil fuel and CO2 emissions, is causing sea temperatures to rise - leading to the loss of marine wildlife and habitats and threatening the processes that allow the oceans to store carbon.