Things got really weird in the waters of Southern California in 2015.
Temperatures in the Pacific Ocean rose to 10 degrees Fahrenheit above average, as an unprecedented warming trend extended from Alaska to Mexico.
It was a wave of marine heat in good faith.
In a study published Tuesday in the journal Nature Communications, researchers concluded that since 1925, the number of days of marine heat waves increased by more than 50 percent per year, and the frequency of events increased by almost 35 percent. And our warm climate could be the culprit.
As oceans absorb heat from a warming Earth, average ocean temperatures have been increasing, which facilitates extreme events of marine warming.
During the great heat wave event that caused the event near the southern coast of California, several creatures that inhabit the sea died, including sea lions, birds and possibly almost 50 whales.
Unlike heat waves on land, marine heat waves absorb much more heat than air, resulting in long-lived extremes.
"Sometimes heat waves in the ocean can be very long," Emanuele Di Lorenzo, marine scientist at the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology, who was not involved in the study, he said in an interview.
Di Lorenzo cites the 2014-2015 "warm blob" event in the Pacific Ocean, which lasted more than a year.
"That opened everyone's eyes," said Di Lorenzo. "And, of course, it has mbadive implications for living beings."
When the oceans are cooked, the consequences for marine creatures are likely to be similar to those of terrestrial heat waves for people.
Terrestrial heat waves "tend to be the most deadly weather phenomena," said Bill Patzert, a NASA climatologist at the Jet Propulsion Laboratory who was not involved in the study. He cites the infamous 2003 heatwave of Europe, which killed some 70,000 people.
Marine heat waves, however, are not as well documented, but they are already known to be devastating, Patzert said. For example, extreme heat waves have repeatedly hit the Great Barrier Reef, northeast of Australia. In 2016, this warming event contributed to the extinction of almost 70 percent of the shallow-water corals in a 430-mile area of the most pristine reef.
In this case, a sea heat wave exacerbated already abnormally high ocean temperatures. Large stretches of stressed coral were essentially kicked when they were already low.
"It's a compound pain," said Di Lorenzo.
In the study, researchers attributed these rising heatwave trends to the rising average of global ocean temperatures. The warmer oceans simply facilitate temperatures to jump to such extreme levels.
"This means that you will have times when you will have a better chance of reaching the warming thresholds," said Di Lorenzo.
Although the study's researchers returned to sea surface temperature data from more than a century ago, the best data come after 1982, said Di Lorenzo. Specifically, this means the inclusion of satellite data collected by satellites of the National Oceanic and Atmospheric Administration (NOAA) over the course of more than 30 years.
"There is no doubt that there is a trend," Di Lorenzo said of the increase in the duration and frequency of marine heat waves. But he warns that this data set (1982-2016) covers a period of time too short to say that the rebound of heat waves is due to climate change. The increase in observed heat waves could be due to natural changes in temperature in the ocean, as opposed to a consequence of global warming.
That said, it is clear that the average temperature increase measured in the oceans today is undeniably caused by human-induced climate change. About 95 percent of the radiation from the sun that is trapped in the atmosphere is absorbed by the oceans.
"The unequivocal proof of global warming is the warming of the oceans, it's quite simple," said Patzert.
Events of extreme warming in the ocean will be especially frequent around longer-term warming trends that may last for years or longer, Patzert said. This includes El Niño events in the Pacific Ocean and the longer-term Pacific Ten-Year Oscillation, which can heat vast regions of the Pacific Ocean for decades.
"Somehow, extreme events in the ocean, like on earth, can be more punishing than slower movement events," said Patzert. The oceans are already suffering from pollution and overfishing. "Then, when you accumulate it with these waves of marine heat, then it simply aggravates the situation, making it more devastating."
Ocean temperatures will almost certainly continue to rise this century. However, if there is a sustained global effort to mitigate the release of greenhouse gases into the atmosphere, the severity of the increase could be limited.
In the United States, however, the government tries to move from burning fossil fuels to renewable energy as solar has been blocked by the embattled head of the Environmental Protection Agency, Scott Pruitt. Pruitt hopes to revoke the Clean Energy Plan, President Obama's plan to strip the nation of the fossil fuels that trap the heat.
"We live in a warmer world and we are exacerbating it," said Patzert.