The latest special report from the Intergovernmental Panel on Climate Change (IPCC) comes after countries met at the UN in a push to increase efforts to cut emissions to avoid the worst impacts of global warming.
The new study, which examines the oceans, coasts and the cryosphere - frozen areas of the world - is expected to warn of huge increases in flooding damage, melting ice caps and glaciers and more ocean heatwaves that bleach and kill coral.
More than 100 scientists from around the world have assessed the latest science about the role of climate change on ocean, coastal, polar and mountain systems, and the human communities that depend on them.
The final draft, which has been agreed by countries meeting in Monaco, is also expected to warn of damage to fish stocks and seafood which millions rely on.
And an increase in extreme El Ninos – a weather phenomenon in the Pacific which pushes up global temperatures and can cause an increase in wildfires – is also on the cards.
The world’s oceans absorb much of the extra heat being generated by global warming and take in a proportion of the emissions of carbon dioxide, making the seas more acidic which can damage sea creatures.
The report is expected to cover what can be done to alleviate the problems, such as the importance of protecting the oceans and restoring habitats which absorb and store carbon such as sea grass beds in shallow waters.
Ahead of the report’s launch, Greenpeace International scientist, Melissa Wang, said: “We expect the IPCC report to confirm our worst fear – the climate crisis is an oceans crisis.
“Some of the impacts of climate change on our oceans are now irreversible and others are looking increasingly inevitable.”
And she warned: “At current emissions rates, we are effectively dumping one million tonnes of carbon dioxide into the oceans every hour.
“Unless we accelerate efforts to curb carbon emissions and take greater steps to protect our oceans, there will be devastating human, environmental and economic consequences.”