Sign up for our daily briefing

Make your busy days simpler with Axios AM/PM. Catch up on what's new and why it matters in just 5 minutes.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on the day's biggest business stories

Subscribe to Axios Closer for insights into the day’s business news and trends and why they matter

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Stay on top of the latest market trends

Subscribe to Axios Markets for the latest market trends and economic insights. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sports news worthy of your time

Binge on the stats and stories that drive the sports world with Axios Sports. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Tech news worthy of your time

Get our smart take on technology from the Valley and D.C. with Axios Login. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Get the inside stories

Get an insider's guide to the new White House with Axios Sneak Peek. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Axios on your phone

Get breaking news and scoops on the go with the Axios app.

Download for free.

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Denver news?

Get a daily digest of the most important stories affecting your hometown with Axios Denver

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Des Moines news?

Get a daily digest of the most important stories affecting your hometown with Axios Des Moines

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Twin Cities news?

Get a daily digest of the most important stories affecting your hometown with Axios Twin Cities

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Tampa Bay news?

Get a daily digest of the most important stories affecting your hometown with Axios Tampa Bay

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Charlotte news?

Get a daily digest of the most important stories affecting your hometown with Axios Charlotte

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sign up for Axios NW Arkansas

Stay up-to-date on the most important and interesting stories affecting NW Arkansas, authored by local reporters

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Snorkeler surveying bleached coral in the Maldives in 2016, during the third global coral bleaching event. Photo: XL Catlin Seaview Survey

Tens of millions across the northern hemisphere have experienced record heat waves this summer, further driving home how climate change is already tilting the odds in favor of more severe extreme heat events in the years ahead.

A similar dynamic is emerging in our oceans, and this could have far-reaching implications. A new study, published today in the journal Nature, finds that marine heat wave days have doubled between 1982 and 2016, which cannot be explained by natural variability alone. What's new and significant, though, is what the study projects for the future.

Why it matters: Marine species that already live close to the upper end of their heat tolerance could perish in prolonged and more severe marine heatwaves in the near future — much as portions of the Great Barrier Reef did during the 2014 to 2017 global coral bleaching event.

  • Recent studies have shown that the frequency of marine heat waves has increased in the past several decades, but a lot has remained unknown about these events, until now.

How they did it: The new study uses satellite observations of ocean temperatures during the period from 1982 to 2016, combined with a suite of Earth system computer models to provide more insight into the likelihood and severity of such phenomena. The researchers identified an event as a marine heat wave when the sea surface temperature exceeded its local 99th percentile.

What they found: The study's findings are grim, as they indicate that global warming is already sharply raising the risk of marine heat waves, and this is likely to get significantly worse.

According to Thomas Frölicher, lead author of the study and a researcher at the University of Bern in Switzerland, if greenhouse gas emissions continue on their present course and temperatures were to rise by 6.3°F (3.5°C) by 2100, "the number of marine heatwave days will be 41 times higher than in preindustrial times," he told Axios.

  • "On average, the spatial extent of the heatwaves would be 21 times larger, their duration would increase to 112 days and their maximum intensity would rise to 2.5°C," or 4.5°F.
  • "The probability of marine heat waves is projected to increase almost everywhere," Frölicher said.
  • However, these numbers would decrease significantly if emissions are cut, and global warming were to be limited to just 1.5°C, or 2.4°F, above preindustrial levels, the study found.

Interestingly, the study found that the number of marine heat waves is increasing faster than the number of heat waves on land.

Sea surface temperature anomalies in March 2015, showing the northeastern Pacific "warm blob." Photo: NASA Earth Observatory
"Since sea surface temperatures warm slower than temperatures over land one would expect marine heatwaves to increase slowly. However, since temperatures are less variable in the ocean than over land, this occurs more rapidly."
— Erich Fischer, study coauthor

How it works: Marine heat waves can trigger large-scale changes in marine ecosystems, killing some species or forcing them to move.

"Recent observed marine heatwaves, such as the marine heatwave in Western Australia in 2011 or the blob in the North Pacific from 2013 to 2015, demonstrated the high vulnerability of marine ecosystems to such events," Frölicher said.

"Reported biological impacts range from geographical species shifts and widespread changes in species composition to harmful algal blooms, mass stranding of mammals and mass mortalities of particular species. In several cases, marine heatwaves have led to the closing of commercially important fisheries and aquaculture industries."
— Thomas L. Frölicher, study lead author

What we're watching: The new study goes a long way toward attributing trends in marine heat waves and projecting what may lie ahead. However, according to Frölicher, scientists currently lack a full understanding of the processes behind the formation of a marine heat wave, as well as the decay of such events. Researchers and scientists alike will need to do more work to understand how marine ecosystems will respond to more of these events.

Eric Oliver, a physical oceanographer at Dalhousie University in Nova Scotia who led a prior study on marine heat waves, said the new research is noteworthy for "quantifying the future projected changes.”

“It’s a very important issue in part because it’s so easy to ignore. When we see heat waves on land it’s obvious that people are dying," Oliver said. "It’s just much more obvious. Whereas unless you spend your life underwater, which very few people do… it’s really hard to see the impacts.”

The bottom line: The finding that oceans are facing a similarly scorching future as land areas is yet another warning that without sharp cuts in greenhouse gas emissions, we're in for a far more volatile and damaging future than we've been accustomed to.

"Together with the projected increase in marine heatwaves with future warming, this provides a worrying picture for the global oceans," Fischer says.

Go deeper

Updated 5 mins ago - Sports

Olympics dashboard

📺: The Olympic events to watch today; Olympics opening ceremony ratings plunge

🏊: Athlete spotlight — Katie Ledecky adds to Games career medals haul; Caeleb Dressel wins gold.

🏀: U.S. Men's basketball suffers first Olympic loss since 2004

🤖: The robot Olympics

🚨: Heat wave brings scorching temperatures to Tokyo Olympics

🎤: Meet the new faces of NBC's Olympics coverage

Go deeper: Full Axios coverage

1 hour ago - Sports

Olympics opening ceremony ratings fall to 33-year low

Wally Skalij /Los Angeles Times via Getty Images

Ratings for the Olympic Games opening ceremony were down 36% compared to 2016, according to preliminary numbers from NBC Universal. 

Why it matters: The figures for the Tokyo Games event mark the lowest audience for an Olympics opening ceremony event in over three decades, per Reuters.

California's largest wildfire razes homes as 86 huge blazes burn in West

A burnt Corvette smolders at a property during the Dixie Fire in the Indian Falls area of unincorporated Plumas County on July 25. Photo: Josh Edelson/AFP via Getty Images

California's biggest wildfire merged with another blaze as it razed homes in a remote region in the state's north Sunday.

The big picture: The Dixie Fire, which erupted July 14 near the origin of the deadly 2018 Camp Fire in Butte County, is one of 86 large wildfires burning across the U.S. West.