Our oceans are much warmer than we previously thought, according to a new study. They are also heating up faster than was believed, driven by climate change caused by humans.
The study, published this week in the journal Science, showed that the world’s oceans have got much warmer since the 1960s. Its authors said 2018 would be the warmest year on record for oceans.
But what happens when the oceans get warmer, and what does it mean for us?
Rising sea levels
When water heats up, it takes up more space. That means as oceans warm, sea levels rise. The study says this effect alone could make sea levels rise 30cm (12 inches) by the end of the century.
“That doesn’t sound like much, but there are many large cities around the world, much built on reclaimed land, that are not more than 30cm above sea level,” says Stephen Simpson, associate professor in marine biology and global change at the University of Exeter, in the UK. “Millions and millions of people would be displaced.”
But on top of that, warming oceans are causing polar ice sheets to melt faster, which will make sea levels rise even more.
Read: 15 facts about sea level rise
The combination of melting ice and expanding water could cause sea levels to rise by up to a meter by 2100. Hundreds of millions of people could be forced to leave their homes.
Rising sea levels are already causing more flooding in the US, and within the next 30 years, more than 300,000 US homes could be flooded every other week, according to research from the Union of Concerned Scientists.
Extreme weather gets more extreme
Warmer oceans make tropical storms more intense and longer lasting.
Hurricane Harvey, which brought more than 1.5 meters (60 inches) of rain over four days in late August 2017, was made worse by unusually warm ocean temperatures.
For coastal areas already struggling with rising seas, those storms will bring even more flooding.
Read: Yes, climate change made Harvey and Irma worse
Warming temperatures also mean changing rainfall patterns. “We’ll probably be seeing redistributing of water vapor in the atmosphere,” says Brad Linsley, research professor Columbia University’s Lamont-Doherty Earth Observatory. “Higher temperatures lead to more evaporation, so parts of the earth will get wetter and parts will get drier.”