Oceans had hottest year on record in 2018 as global warming accelerates
Earth’s oceans had their warmest year on record in 2018, a stark indication of the enormous amount of heat being absorbed by the sea as greenhouse gas emissions continue to rise, scientists reported Wednesday.
The analysis by an international team of scientists confirms the oceans are heating up much faster than previously recognized, and that the pace of warming has accelerated sharply since the 1990s.
Rising ocean temperatures are already having profound consequences across the globe, scientists say, contributing to more intense hurricanes, destroying coral reefs and causing sea levels to rise.
The report in the journal Advances in Academic Sciences builds on a study last week that found oceans are warming 40 percent more, on average, than was estimated by a United Nations scientific panel just five years ago. In fact, each of the last 10 years is among the 10 warmest on record, according to data from Lijing Cheng of the Institute of Atmospheric Physics in Beijing, who led the research.
The unrelenting pattern is “incontrovertible proof that the Earth is warming,” and an unmistakable signal of the serious damage humans are already causing through climate change, the authors of the new study wrote.
Earth’s oceans provide a crucial buffer against climate change by swallowing 93 percent of the excess heat trapped by the greenhouse gases humans are spewing into the atmosphere.
“The oceans are really the Earth’s thermometer,” said Zeke Hausfather, a climate scientist with the academic nonprofit Berkeley Earth who collaborated on the research. “They’re where all the heat ends up. They’re where we’d expect the strongest signs of climate change to be. And that’s exactly what we see.”
In contrast with rising surface temperatures, which can vary from year to year with the influence of weather and cyclical climate patterns like El Nino, the warming of the ocean has been inexorable, with virtually every year breaking the heat record set just 12 months earlier.
“There’s no sign of any slowdown or pause,” Hausfather said. “The ocean temperature is increasing year over year in lockstep with increases in atmospheric carbon dioxide and other greenhouse gases.”
Indeed, emissions have accelerated as President Donald Trump and some other world leaders have pursued energy policies that promote fossil fuels. Global carbon emissions increased 1.6 percent between 2016 and 2017, then jumped an additional 2.7 percent in 2018, according to estimates published last month in the journal Environmental Research Letters. Last week, the research firm Rhodium Group reported that U.S. carbon emissions rose 3.4 percent in 2018 after years of declines.
Rather than measure the water’s temperature, the researchers focused on the amount of energy the oceans had taken in. They determined that the heat content has increased by around 370 Zettajoules since 1955. The increase in 2018 alone compared with 2017 — about 9 Zettajoules — was about 100 million times greater than the heat released by the atomic bomb dropped on Hiroshima, Japan, Hausfather said.
The rate of warming in the ocean’s upper 6,500 feet has been up to five times faster since 1991 than it was in the 1970s and ‘80s, scientists found. The warming is more pronounced in shallower waters, with about two-thirds of the energy accumulating within 2,000 feet of the surface.