Jan Pappas and Ronald Yasuda hired a contractor to fasten the roof of their 1960s-era home to their walls with metal plates and nails so high winds of a potential hurricane wouldn't blow it away.

Their motivation? Global warming fueling natural disasters around the planet.

"It’s happening right now, every place in the world," said Pappas, who installed the so-called hurricane clips after watching extreme weather in other parts of the world. "How are we to expect that it’s not going to happen here to us?"

Many of Hawaii's homes are even more vulnerable than theirs. Two-thirds of the single-family homes on Oahu, an island of 1 million people that's home to Honolulu, have no hurricane protections. That lack of preparedness is unnerving residents this hurricane season as the islands prepare for the possibility of a one-two weather punch: the increased odds of a tropical cyclone that come with any El Nino year combined with climate-fueled ocean warming that could mean bigger and more frequent tropical storms around the islands overall.

El Nino, a naturally occurring warming of equatorial waters in the central and eastern Pacific, affects weather worldwide. Already this year, Hawaii has felt its wrath as a tropical storm passed south of the Big Island last month. On top of that, warming oceans heated by climate change could strengthen tropical storms and nudge them farther north, potentially putting them on a collision course with Hawaii.

Hawaii's experience stands in contrast to the U.S. territory of Guam, where stronger building codes and years of rebuilding after powerful storms means most homes are now made of sturdy concrete. In May, a Category 4 typhoon with maximum sustained winds of 150 mph slammed into the island. The storm destroyed some older homes, but the concrete ones generally emerged unscathed.

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Many of Hawaii's single-family homes are single-wall construction, a style phased out only in the 1970s, said Gary Chock, a licensed structural engineer.

Hawaii's temperate climate means homes don't need to trap heat, so most don't have an additional wall to contain insulation. Structurally, their foundations aren't often properly anchored to the ground. Their lower cost made them Hawaii's preferred construction style for decades.

They proved particularly vulnerable to powerful winds during Hurricane Iwa, which just missed Kauai in 1982, and Hurricane Iniki, which slammed directly into Kauai a decade later.

"The entire roof of the home might be decapitated by wind," Chock said of single-wall homes hit by Iniki. "And the whole roof, in one piece, would just fly off the walls, and the rest of the structure would fall apart thereafter."

Iniki damaged or destroyed 41% of Kauai's 15,200 homes with 130- to 160-mph winds. Seven people were killed, and 100 were injured.

After Iwa, new homes had to have their roofs secured to their walls. After Iniki, new construction had to strap upper stories to lower stories and connect the foundation to the first floor.

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Chock said a home built to code today would withstand a Category 3 hurricane, with winds up to 130 mph, if a structural engineer supervised construction. Homes built on mountain ridges and in valleys must be able to withstand higher winds.

Homes built before the building code changes aren't required to have these features, and few homeowners have retrofitted with hurricane clips like Pappas and Yasuda. Sixty-four percent of single-family homes — or 125,000 houses — on Oahu lack any hurricane protections, according to a 2019 study by Honolulu.

Bob Fenton, Federal Emergency Management Agency administrator for the region that includes both Hawaii and Guam, said these homes are more easily damaged by Category 3 or 4 tropical cyclones.

The state is looking at some nonprofit and volunteer programs that could help fortify homes, said James Barros, Hawaii Emergency Management Agency administrator.

"But it starts with the individual house — taking a look at, ‘How vulnerable is my house to winds?’" he said.

Guam already faces ferocious storms with some regularity.

The U.S. territory nearly 4,000 miles west of Hawaii tends to have more — and more powerful — tropical cyclones because its sea surface temperatures are higher. The ocean around Guam is also warmer year-round, so cyclones can form anytime. Such storms are called typhoons west of the international dateline and hurricanes to the east.

Since the early 1990s, four typhoons with sustained winds of at least 150 mph have directly hit Guam, including Typhoon Mawar in May. By contrast, Hawaii has only had one such powerful storm, Iniki.

Guam has become more resilient after each storm, often by rebuilding with concrete capable of withstanding Category 4 and 5 typhoons.

Those homes are more expensive to build, and they trap heat and radiate warmth at night when people need to sleep — a problem that could worsen with global warming.

To cool their homes, many people on Guam paint their roofs white to deflect the sun or plant rooftop gardens, said Kyle Mandapat, a spokesperson for University of Guam Sea Grant. Mandapat has even heard of people installing rooftop sprinklers and using drains to catch the water to irrigate their gardens.

More concrete leads to more air conditioning, which can also be expensive. It's all a lot, but "people still see that as more of something they can deal with as opposed to the prospect of their house blowing away," Mandapat said.

Concrete homes are rare in Hawaii, but new homes are being built with pricey hurricane-resistant features.

Daryl Takamiya, a past president of the Building Industry Association of Hawaii, said the hurricane-resistant windows his company is installing at a suburban Honolulu development add $25,000 to $30,000 to the cost of each new home. A hurricane-resistant garage door adds another $1,600. The homes are being built to withstand winds of up to 130 mph.

"There’s always a drawback, right?" Takamiya said. "I mean, you can build homes that are basically bunkers, but you’re going to pay for it."

The high cost of Hawaii homes is already driving an exodus of residents to other states, including many Native Hawaiians. Family homes at Takamiya's suburban development start at $940,000, just under the Oahu median price of $1.03 million.

Yet these hurricane-resistant homes may become more necessary in Hawaii as the planet warms.

John Bravender, the warning coordination meteorologist for the National Weather Service in Honolulu, pointed to a 2014 study showing that as oceans have warmed, tropical cyclones in the northern hemisphere have been drifting farther north, and those in the southern hemisphere have been moving further south.

For Hawaii, that means hurricanes that would have previously passed south of the Big Island may now be more likely to hit the island chain. And unlike Tropical Storm Calvin, which lost its hurricane status as it approached the Big Island last month, they may maintain strength.

"So far, cross our fingers, nothing has really happened," said Yasuda, the homeowner, referring to the many close calls Oahu has had. "I don’t know how long we can hope that nothing happens, you know?"