Oceans reached highest temperature on record in 2019

Last year saw the highest ever temperatures recorded in the Earth's oceans, adding more urgency to the climate emergency, according to the findings of a new study by Advances in Atmospheric Sciences. 

The journal this week published its study 'Record setting ocean warmth continued in 2019'. In it, it says more than 90 percent of the excess heat produced by greenhouse gases, which are created by us humans, is stored in the oceans.

“It drives home the fact that climate changes continues unabated,” Michael Mann tells RFI, professor of Atmospheric Science at Penn State University and one of the authors of the study.

Mann is currently in Australia where massive bushfires have been raging since Septmber.

“We're seeing it in the form of unprecedented heat, drought and bushfires... We must put a lot more pressure on our politicians to act now before it is too late," he says.

Understanding the significance
The science of this study stands out more than others in the accuracy of the data provided, according to Kevin Trenberth, a scientist with the Climate Analysis Section at the National Center for Atmospheric Research in the US, another co-author of the study.

Many studies in the past discussed the warming of global mean surface temperatures. "But you need to have a record of about 15 to 20 years before you can confidently say that the trend is upwards,” Trenberth tells RFI.

This latest study uses much more accurate ways of measuring the ocean heat content, Trenberth says, which means four years of records are sufficient to confirm that the planet is warming.

With such studies, it can be difficult to understand and conceptualise the implications – which may in turn make it easier to dismiss.

Put simply: “When you put a pot of cold water on the stove and turn on the element to boil, it takes quite a while. There's a tremendous amount of heat that goes into that,” explains Trenberth.

“It indicates that the oceans have tremendous heat capacity – even a small increase in the temperature involves a very large amount of heat,” he adds.

As the oceans continue to absorb heat from the atmosphere, it diminishes their ability to moderate climate change. "We can see that sort of thing in Australia with the bushfires and the heat waves,” Trenberth notes.

With the added heat, comes more glaciers melting and an increase in sea levels. That has major consequences in the long term, which has led to “marine heat waves”, such as one in the North Pacific called the 'Blob' that killed 100 million cod fish. Or seeing tropical fish where they have never been seen before, and witnessing ever more devastating storms, such as Hurricane Harvey in 2017 or Florence in 2018, or the recent flooding in the Indonesian capital Jakarta.

What can be done if it's too late
“We're past that point,” stresses Tim Boyer to RFI, another author on the study who heads the Ocean Climate Laboratory Team at the National Centers for Environmental Information.

“We can always do something to ameliorate future effects, but there's nothing that we can do for the heat that's already been accumulating in the system,” says Boyer.

The problem, as Mann points out, is that even if we stop emitting carbon into the atmosphere, the oceans will continue to heat up for decades.

“The sooner we get off fossil fuels, the sooner the warming stabilises,” he stresses.

Trenberth says he's been highlighting this problem since the 1990s.

“For something to really happen, it requires US leadership along with China and Europe. Together those three could basically solve the problem, or at least put us on the right path to solving it. It just requires the right leadership in the right places and we could make huge progress.”