The world’s ocean temperatures hit a new record high in 2019, showing “irrefutable and accelerating” heating of the planet.
The oceans worldwide are the most transparent measure of the climate emergency as they absorb 90% and even more of the heat trapped by the emission of greenhouse gases from fossil fuel burning, forest destruction, and other human activities.
The last five years are the top five warmest years in the ocean recorded, and the previous decade or last 10 years are also the top 10 years on record, the new analysis shows. The amount of addition of heat that added to the oceans is equivalent to 100 microwave ovens run by every person on the planet all day and all night.
More hot oceans mean more severe storms that disrupt the water cycle and cause more floods, droughts, and wildfires, finally an inexorable rise in sea level. Higher temperatures are also sharply increasing the number of marine heatwaves harming life in the seas.
The average surface air temperature is the most common measure of global heating that humans can feel. But natural climate phenomena like El Niño events make this parameter vary from year to year.
“The oceans are really what tells you how fast the Earth is warming,” said Prof John Abraham at the University of St Thomas, in Minnesota, US, and one of the teams behind the new analysis. “Using the oceans, we see a continued, uninterrupted, and accelerating warming rate of planet Earth. This is dire news.”
“We found that 2019 was not only the warmest year on record, it displayed the largest single-year increase of the entire decade, a sobering reminder that human-caused heating of our planet continues unabated,” said Prof Michael Mann, at Penn State University, US, and another team member.
The ocean data from every available source is used in the analysis published in the journal Advances in Atmospheric Sciences. The maximum number of data is from the 3,800 free-drifting Argo floats dispersed across the oceans, and even from torpedo-like bathythermographs dropped from ships earlier.
As the accumulation of greenhouse gases increases in the atmosphere, the heat increases at an accelerating rate, the results show. The rate from 1987 to 2019 is 4 ½ times faster than that from 1955 to 1986. The vast ocean regions are mostly showing an increase in thermal energy.
This energy drives bigger storms, and more extreme weather said Abraham: “When the world and the oceans heat up, it changes the way rain falls and evaporates. There’s a general rule of thumb that drier areas are going to become drier and wetter areas are going to become wetter, and rainfall will happen in bigger downbursts.”
The sea levels are also to rise as the hotter oceans expand and melt ice. The last decade also shows the highest sea level measured in records dating back to 1900. Scientists expect around another meter of sea-level rise by the end of the century, and that will be enough to displace 150 million people worldwide.
Dan Smale, at the Marine Biological Association in the UK, and not part of the analysis team, thinks that the methods used are state of the art, and the data is the best available. “For me, the take-home message is that the heat content of the upper layers of the global ocean, particularly to 300-meter depth, is rapidly increasing, and will continue to increase as the oceans suck up more heat from the atmosphere,” he said.
“The upper layers of the ocean are vital for marine biodiversity, as they support some of the most productive and rich ecosystems on Earth, and warming of this magnitude will dramatically impact on marine life,” Smale said.
According to the new analysis, the heat is in the top 2,000m of the ocean from where most of the data is collected. It is the home to most marine life where the vast majority of the heat accumulates.
The researchers at the Chinese Academy of Sciences in Beijing developed the analysis method and use statistical methods to interpolate heat levels in the few places where there was no data, such as under the Arctic ice cap. The US National Oceanographic and Atmospheric Administration (NOAA) shows the same increasing heat trend in an independent analysis of the same data.
The reliable ocean heat measurements stretch back to the 20th-century middle. But Abraham said: “Even before that, we know the oceans were not hotter.”
“The data we have is irrefutable, but we still have hope because humans can still take action,” he said. “We just haven’t taken meaningful action yet.”