An international team released the 2018 ocean heat content observations on Wednesday. The newly available observations show that the year 2018 is the hottest year ever recorded for the global ocean, as evident by the ocean heat content in the upper 2000m.

Compared to the average value for 1981 - 2010, the 2018 ocean heat anomaly is approximately 19.67 x 10²² Joules (a unit measure for heat). This heat increase in 2018 relative to 2017 is 0.91 x 10²² Joules, ~388 times more than the total electricity generation by China in 2017, and ~100 million times more than the Hiroshima bomb energy. The years 2017, 2015, 2016 and 2014 are ranked next. The values are based on an ocean temperature analysis product conducted by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences.

The new study is shedding new light onto how much oceanic water temperatures have been changing over the years. The change in ocean heat content is considered to be one of the best - if not the best - way to measure climate change driven by greenhouse gases emitted by human activities. This is because the global warming is driven by the Earth’s energy imbalance due to more greenhouse gases in the air from human activities including burning fossil fuels, and the vast majority (more than 90%) of global warming heat is deposited in the world’s oceans.

Also, ocean heat record is less impacted by natural fluctuations than surface temperatures and it is a robust indicator of climate change. Therefore, record-breaking ocean heat record serves as direct evidence for global warming and highlights the need for adaptation to and mitigation of climate change.

The findings were reported in a News & Views article in Advances in Atmospheric Sciences in January of 2019.

The article is highlihgted on the cover of March Issue of Advances in Atmospheric Sciences (AAS). The increasing heat-trapping gases, such as carbon dioxides represented by a bird in the cover, produce an energy imbalance that leads to global heating (fires in the cover). Most of the heats end up deposited in the world’s oceans and the others melt the ice, warm the atmosphere and land. (Image by AAS) 

"The new data, together with a rich body of literature, serve as an additional warning to both the government and the general public that we are experiencing global warming. The ocean and global warming are taking place and cause serious damage and losses to both the economy and society," states  Dr. CHENG Lijing, the lead author of the study. He also recommends additional actions to be taken immediately in order to minimize future warming trends.

The researchers also highlight that the increases in ocean heat through warmer waters, which they prognosticate will continue to rise, are causes for additional concern to both the scientific community as well as the public at large. Higher temperatures result in an increase of sea level that comes with its own set of consequences. Examples include salt water contaminating fresh water wells which impacts the quality of drinking water, a compromised coastal infrastructure as well as increased likelihoods of storms. Increases in ocean heat also have severe consequences for the global weather system because they result in more water vapor and thus much more intense storms and heavy rains.

Other consequences of increasing ocean water temperatures include bleaching and death of corals, melting sea ice, increasing marine heat waves, and long periods of extreme surface temperatures, as well as impacts on natural variability. Ocean heating has also been connected to increased drought intensity, heatwaves and risks to wildlife.

The researchers' future aims focus on a deeper understanding of the effects of warmer ocean waters. As such, the IAP and collaborators will continue to monitor trends as well as focus on understanding the climate system as well as the ocean's role in it.

By better understanding the changes and potential dangers accompanying increasing ocean heat, researchers hope their work will prove to be a valuable resource to the construction, fishing, and tourism industries. "These scientific activities will eventually serve the general public and government as a basis for them to make informed decisions and thus create a better and more sustainable future for all," CHENG adds.