Ocean warming is irrefutable, they say.
The world's oceans last year were the warmest they have been since records began, a new analysis has claimed.
The paper, published in the Advances in Atmospheric Sciences, said the past five years had also been the five warmest for sea temperatures.
"The ocean heating is irrefutable, and a key measure of the Earth’s energy imbalance: the excess GHGs (greenhouse gases) in the air trap more heat inside the climate system and drives global warming," wrote the team behind the study, which consisted of 14 scientists from 11 institutes across the world.
"More than 90% of the heat accumulates in the ocean because of its large heat capacity, and the remaining heating manifests as atmospheric warming, drying and warming landmass, and melting of land and sea ice."
"Increases in ocean temperature reduce dissolved oxygen in the ocean and significantly affect sea life, particularly corals and other temperature- and chemistry-sensitive organisms.
"The increasing heat increases evaporation, and the extra moisture in the warmer atmosphere nourishes heavy rains and promotes flooding, leading to a more extreme hydrological cycle and more extreme weather (in particular hurricanes and typhoons).
"It is one of the key reasons why the Earth has experienced increasing catastrophic fires in the Amazon, California, and Australia in 2019."
To understand how fast things are changing, John Abraham, co-author of the study, encourages people to look at oceans.
"The key to answering this question is in the oceans - that's where the vast majority of heat ends up. If you want to understand global warming, you have to measure ocean warming," he explained.
The year 2019 broke previous records set in previous years for global warming, and the effects are already appearing in the form of more extreme weather, sea level rises and damages to ocean animals.
But the scientists highlight a silver-lining thought in this study. Indeed, they comment that the effects on climate can still be reversed. But the oceans will take longer to recover, they insist.