A surprising side effect of climate change in Hawaii? More rainbows

More rainbows are expected in Hawaii’s future due to climate change, scientists predict.
More rainbows are expected in Hawaii’s future due to climate change, scientists predict.(Steven Businger via University of Hawaii)
Published: Nov. 3, 2022 at 3:11 PM HST|Updated: Nov. 3, 2022 at 3:57 PM HST
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HONOLULU (HawaiiNewsNow) - Scientists have determined a bright spot in a new climate change study: More rainbows are expected in Hawaii’s future.

The study, led by a team of University of Hawaii researchers, predicts that by 2100, the world will experience about 5% more days with rainbows than at the beginning of the 21st century.

That’s because a warmer atmosphere, caused by human activities like burning fossil fuels, are changing patterns and amounts of rainfall and cloud cover.

Sunlight and rainfall are vital to the formation of rainbows, which are created when water droplets refract sunlight.

To get their findings, a team, including UH-Manoa students, sorted through photos on Flickr of rainbows from around the world and used a prediction model based on photo locations and maps of precipitation, cloud cover and the angle of the sun.

Using the data, they were able to train a model to predict present day and future rainbow occurrences across the globe. It found that islands, like the Hawaiian islands, are rainbow hotspots.

Hawaii is already dubbed the “rainbow capital of the world,” but researchers predict the islands will see a few more days with rainbows per year.

“Islands are the best places to view rainbows,” said Steven Businger, professor of Atmospheric Sciences at UH Manoa’s School of Ocean and Earth Science and Technology, in a statement.

“This is because island terrain lifts the air during daily sea breezes, producing localized showers surrounded by clear skies that let the sun in to produce majestic rainbows.”

According to the research, northern latitudes and high elevations will see the biggest gains, while places with reduced rainfall, such as the Mediterranean, will see fewer rainbows in the sky.

A simple question sparked the idea for this study.

“Living in Hawaii, I felt grateful that stunning, ephemeral rainbows were a part of my daily life,” said Kimberly Carlson, the lead author of the study who is now at New York University’s Department of Environmental Studies. “I wondered how climate change might affect such rainbow viewing opportunities.”

Camilo Mora, of the UH Manoa Department of Geography and Environment, was intrigued by the thought and pitched it as the focus of a project for one of his graduate courses.

“We often study how climate change directly affects people’s health and livelihoods, for instance via the occurrence of heat stroke during climate change-enhanced heat waves,” he said. But he added that few researchers have looked into how it might affect the aesthetics and none had mapped out rainbow occurrences due to climate change.

Though there is little known on how rainbow occurrence might affect human wellbeing, researchers say they’re an important part of human culture throughout history and are aesthetically pleasing.

To view the full study, click here.