Climate change will increase the chances of seeing rainbows, according to a new study by researchers at the University of Hawai’i (UH) at Mānoa. The study authors estimate that by 2100, the average land location on Earth will experience about 5% more days with rainbows than at the start of the 21st century.
Northern latitudes and very high altitudes, where warming is expected to bring less snow and more rain, will see the greatest gains in rainbow occurrence. However, places with reduced rainfall due to climate change, such as the Mediterranean, are expected to lose rainbow days.
Rainbows are produced when water droplets refract sunlight. Sunlight and precipitation are therefore essential ingredients for rainbows. Human activities such as the burning of fossil fuels warm the atmosphere, which changes precipitation patterns and amounts and cloud cover.
“Living in Hawai’i, I felt grateful that beautiful ephemeral rainbows were part of my daily life,” said the study’s lead author, Kimberly Carlson, who is now in the Department of Environmental Studies at New York University. “I wondered how climate change might affect these rainbow viewing opportunities.”
Camilo Mora, from the Department of Geography and Environment at UH Mānoa, was intrigued by the question and presented it as the subject of a project for one of his postgraduate courses.
According to Mora, “We often study how climate change directly affects people’s health and livelihoods, for example through the occurrence of heatstroke during climate change-enhanced heat waves.”
However, few researchers have examined how climate change might affect the aesthetic qualities of our environment, and no one had bothered to map rainbow occurrences, let alone under climate change.
To answer this question, a team including students from UH Mānoa reviewed photos uploaded to Flickr, a social media platform where people share photos. They sorted through tens of thousands of photos taken around the world, tagged with the word “Rainbow,” to identify rainbows generated by the refraction of light by rain droplets.
Amanda Wong, then an undergraduate student in Global Environmental Science at UH Mānoa School of Ocean and Earth Science and Technology (SOEST) and co-author of the paper, noted, “We had to sort through photos of rainbow artwork, rainbow flags, rainbow trout, rainbow eucalyptus, and rainbow foods. sky to find the real rainbows.”
Next, the scientists trained a rainbow prediction model based on rainbow photo locations and maps of precipitation, cloud cover and sun angle. Finally, they applied their model to predict current and future occurrences of rainbows over land areas around the world. The model suggests that the islands are rainbow hotspots.
“Islands are the best places to see rainbows,” according to Steven Businger, professor of atmospheric sciences at SOEST. “Indeed, the island terrain lifts the air during daily sea breezes, producing localized showers surrounded by clear skies that let in the sun to produce majestic rainbows.”
The Hawaiian Islands, recently dubbed the “rainbow capital of the world”, should experience a few more days with rainbows per year. The authors stopped short of discussing how changes in the occurrence of the rainbow could affect human well-being. However, rainbows are an important part of human culture throughout history and around the world and are aesthetically pleasing.
“Climate change will cause pervasive changes to all aspects of the human experience on Earth. Changes in the intangible parts of our environment, such as sound and light, are among these changes and deserve more attention from researchers,” Carlson said.
In this case, the overall results are encouraging – it seems that people will have more opportunities to make a rainbow connection under climate change.
The research has been published in Global environmental change.
More information:
Kimberly M. Carlson et al, Global rainbow distribution under current and future climates, Global environmental change (2022). DOI: 10.1016/j.gloenvcha.2022.102604
Provided by the University of Hawaii at Manoa
Quote: Climate change will produce more rainbows, study finds (2022, October 31) Retrieved October 31, 2022 from https://phys.org/news/2022-10-climate-rainbows.html
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