As climate change grows in severity in the coming decades, the islands are expected to see a number of impacts: extreme coastal flooding, warmer temperatures, extended periods of drought, imperiled coral reefs, hurricanes with greater intensity and consequence.

Add a new possibility to the list: no humpback whales.

The findings of a new paper by researchers at the University of Hawaii and the Pacific Whale Foundation suggest that the whales may one day avoid the relatively shallow ocean around the Hawaiian islands because the waters will be too warm.

That could happen by the end of the century if the fossil fuel industry is allowed to further power the global economy and generate unabated carbon emissions, according to the researchers.

“We implore the public to think big and act now,” said Jens Currie, chief scientist at the Pacific Whale Foundation and one of the paper’s authors. “What we do today affects what will happen tomorrow.”

Currie joined Pacific Whale Foundation colleague Stephanie Stack and three UH Manoa graduate students — Hannah von Hammerstein, Renee Setter and Martin van Aswegen — in conducting the modeling study published in May in the journal Frontiers in Marine Science.

It has been estimated that more than 10,000 humpbacks travel each year from Alaska to Hawaii, where they breed and give birth primarily between December and April. The annual migration helps sustain a whale-watching industry said to be worth more than $20 million a year to the state’s economy.

Humpback populations around the globe migrate annually to tropical coastal waters, like Hawaii’s, where sea surface temperatures range between 70 degrees and 82 degrees Fahrenheit. The whales typically return to the same sites every year.

As greenhouse gas emissions warm the world’s oceans at unprecedented rates, the sea surface temperatures in those tropical regions are likely to eventually exceed the normal range for humpback whales.

Although projections of warming seas are out there, they lack the detail and resolution needed to analyze and predict the regional temperature patterns necessary to project changes in humpback whale breeding grounds.

In an effort to map out detailed projections, the researchers employed a statistical analysis known as the delta method to project sea surface temperatures around the world over each decade and highlighted shifting isotherms that matched up with preferred breeding and calving grounds over the course of the current century.

The analysis was initially undertaken as a class project by von Hammerstein and Setter at UH Manoa, who invited co-authors from the UH Marine Mammal Research Program, including van Aswegen, and the Pacific Whale Foundation research team to help interpret the climate projections.

The research suggests two possible climate change scenarios:

>> By 2100, in a worst-case scenario with unabated carbon emissions, 67% of humpback whale breeding grounds will surpass the critical sea surface temperature of 82 degrees Fahrenheit.

>> In a “middle-of-the-road” scenario with global and international institutions working to cutback on emissions, that figure would fall to 35% of breeding grounds.

“We expected to see critical warming in some of the breeding grounds, but the number of critically affected areas was a surprise,” von Hammerstein said.

Currie said the whales may stop going to the breeding grounds if they exceed 82 degrees as the warm habitat would compromise breeding rates, induce chronic stress and impair the fitness of the whales.

Breeding grounds that have few, if any, whales could also inflict economic hardship on countries that rely on whale-based tourism.

The researchers concede that while it is currently not known whether humpback whales will continue to migrate to breeding grounds above 82 degrees, it is very possible they will not.

Currie said studies indicate that in 2015 and 2016, when humpback whale sightings were down drastically in Hawaii, the whales may have been discouraged from making the trek here because of a marine heatwave in the Pacific known as The Blob.

“It was a potential glimpse into the future,” he said.

Currie said the researchers hope their findings will help spur policymakers to work toward reducing emissions.

“It’s really crucial that we try to reduce our greenhouse gas emissions and really try to stay on that ‘middle-of-the-road’ greenhouse gas emissions scenario at the very least,” Setter said.