"If you want to see where global warming is happening, look in our oceans", said Zeke Hausfather, a graduate student in the Energy and Resources Group at the University of California, Berkeley, and co-author of the paper. The thermal expansion caused by this bump in temperature would raise sea levels 30 centimeters, or around 12 inches, on top of the already significant sea level rise caused by melting glaciers and ice sheets.
'Ocean heating is a very important indicator of climate change, and we have robust evidence that it is warming more rapidly than we thought'.
Ocean heating is critical marker of climate change because an estimated 93 percent of the excess solar energy trapped by greenhouse gases accumulates in the world's oceans.
New measurements, aided by an global network of 3,900 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.
Overall, temperatures in the ocean down to 2,000 meters rose about 0.1 degree Celsius (0.18F) from 1971-2010, he said.
Ocean temperatures are less influenced by year-to-year variations in the weather. The report also found that the warming rate has accelerated since 1991. "The global warming signal is a lot easier to detect if it is changing in the oceans than on the surface".
The latest report relied on four studies, published between 2014 and 2017, that gave more precise estimates of past trends in ocean heat, allowing scientists to update past research and hone predictions for the future.
The world's oceans are rising in temperature faster than previously believed as they absorb most of the world's growing climate-changing emissions, scientists said Thursday.
"While 2018 will be the fourth warmest year on record on the surface, it will most certainly be the warmest year on record in the oceans, as was 2017 and 2016 before that", Hausfather said. "That was a problem, because of all things, that is one thing we really hope the models will get right".
For the new study, scientists used data collected by a high-tech ocean observing system called Argo, an worldwide network of more than 3,000 robotic floats that continuously measure the temperature and salinity of the water.
For the last 13 years, an ocean observing system called Argo has been used to monitor changes in ocean temperatures, Cheng said, leading to more reliable data that is the basis for the new ocean heat records.
Three of the new studies included in the Science analysis calculated ocean heat content back to 1970 and before using new methods to correct for calibration errors and biases in the both the Argo and bathythermograph data.
"The fairly steady rise in OHC [ocean heat content] shows that the planet is clearly warming", the report stated, adding that rising sea levels and temperatures should be concerning, "given the abundant evidence of effects on storms, hurricanes and the hydrological cycle, including extreme precipitation events".
This study was supported by the National Key R&D Program of China (2017YFA0603202).