Scientists have warned the oceans are warming faster than previously estimated, setting a new temperature record in 2018 in a trend that is damaging marine life.

New measurements, aided by an international network of 3900 floats deployed in the oceans since 2000, showed more warming since 1971 than calculated by the latest United Nations assessment of climate change in 2013, they said.

Reuters Newsagency reports “observational records of ocean heat content show that ocean warming is accelerating,” the authors in China and the United States wrote in the journal Science of ocean waters down to 2000 metres.

Human-made greenhouse gas emissions are warming the atmosphere, according to the overwhelming majority of climate scientists, and the oceans absorb a large part of the heat.

That in turn is forcing fish to flee to cooler waters.

“Global warming is here, and has major consequences already. There is no doubt, none!” the authors wrote in a statement.

Warming oceans take up more space, a process known as thermal expansion, which the study says is likely to raise sea levels by about 30cm by the end of the century, on top of the rise in sea levels from melting ice and glaciers.

Warmer oceans are also a major factor in increasing the severity of storms, hurricanes and extreme rainfall.

Almost 200 nations plan to phase out fossil fuels this century under the 2015 UN sponsored Paris Agreement to limit warming.

United States President Donald Trump, who wants to promote US fossil fuels, plans to pull out of the Paris Agreement in 2020.

Data due for publication next week will show “2018 was the warmest year on record for the global ocean, surpassing 2017,” said lead author Professor Lijing Cheng, of the Institute of Atmospheric Physics at the Chinese Academy of Sciences.

He told Reuters that records for ocean warming had been broken almost yearly since 2000.

Overall, temperatures in the ocean down to 2000 meters rose about 0.1 degree Celsius from 1971-2010, he said.

The 2013 UN assessment estimated slower rates of heat uptake but did not give a single comparable number.

A separate study, by the European Union’s Copernicus Climate Change Service, said 2018 was the fourth warmest year for global surface temperatures in records dating back to the 19th century.

Ocean temperatures are less influenced by year-to-year variations in the weather.

It can take more than 1000 years for deep ocean temperatures to adjust to changes at the surface.

“The deep ocean reflects the climate of the deep and uncertain past,” Dr Kevin Trenberth, of the US National Centre for Atmospheric Research (NCAR) and a co-author of study, told Reuters.

Among effects, extra warmth can reduce oxygen in the oceans and damages coral reefs that are nurseries for fish, the scientists said.

Warmer seas release more moisture that can stoke more powerful storms.

Warmer ocean water also raises sea levels by melting ice, including around the edges of Antarctica and Greenland.

Separate recently published research extrapolated temperature estimates for the oceans for the past 150 years, and found substantial warming.

Published in the journal Proceedings of the National Academy of Sciences of the United States of America, that research found the total heat taken up by the oceans in the last century and a half was about 1000 times the annual energy use of the world’s population.