By Tim Radford
The ocean waves are now hitting harder than ever. As the world warms, they gain in energy, impact and height.
As the world’s seas warm, the ocean waves are starting to pack more power. Spanish scientists monitoring the tropical Atlantic report that the waves today contain more energy than they did 70 years ago. Sea surface temperatures influence wind patterns, and the payoff is a wave with more impact.
What this means for marine creatures, mariners, meteorologists and the mayors of seaside cities is not yet certain. But it does mean that wave energy could join carbon dioxide atmospheric ratios, global sea level rise and global air temperatures as yet one more metric of overall global warming and climate change.
And Chinese scientists who have been calculating the heat absorbed by the oceans over the last 30 years have confirmed that in 2018 ocean temperatures reached record levels. Before that, 2017 was the hottest oceanic year ever, followed by 2015, 2016 and 2014. Once again, the implications are uncertain: sea levels will rise with ocean temperatures.
“The new data … serve as an additional warning to both the government and the general public that we are experiencing inevitable global warming”
Researchers from the University of Cantabria in Santander, Spain report in the journal Nature Communications that waves have been growing in height in recent decades, and satellite studies confirmed a change of about 1% every four years from 1985 to 2008.
But their research focused on changes in wave energy, important because of the effect wave behaviour has on estuaries, shoals, beaches, dunes, headlands, harbours and sea defences. They examined data from 1948 to 2017 to trace a small but measurable increase in wave energy with the decades.
“For the first time, we have identified a global signal of the effect of global warming in wave climate,” said Borja Reguero, of Cantabria’s environmental hydraulics institute, who is also at the University of California Santa Cruz.
“In fact, wave power has increased globally by 0.4% per year since 1948, and this increase is correlated with the increasing sea surface temperatures, both globally and by ocean regions.”
A hundred million Hiroshimas
Chinese and US researchers recently calculated the heat absorbed by the oceans as ever higher ratios of greenhouse gases – the product of fossil fuel combustion and other human action – are added to the planet’s atmosphere.
Members of the same team report in the journal Advances in Atmospheric Sciences that between 2017 and 2018 alone, the oceans must have absorbed an extra quantity of heat equivalent to 388 times the total electricity generation in China, and – to choose another and more vivid unit of measurement – around 100 million times the heat released by the atomic bomb that in August 1945 destroyed the Japanese city of Hiroshima.
“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 inevitable global warming,” said Lijing Cheng of the Chinese Academy of Sciences, the lead author of the report.
“The ocean and global warming have already taken place and caused serious damage and losses to both the economy and society.”