One of the more unusual consequences of extreme climate change could include an increase in the frequency of rainbows appearing across the globe by 2100 by as much as 5 percent.

Researchers behind a new study modelling the less obvious effects of climate change measure this increase in terms of days in the year with conditions suitable for sighting at least one rainbow.

Using crowd-sourced images, global climate data and a computer model, the scientists found around 21 to 34 percent of land areas will see fewer of these 'rainbow days', with 66 to 79 percent seeing rainbows increase in number as the world warms up.

While more rainbow sightings may not be much consolation in the face of widespread drought and torrential floods, the research team want to see less tangible shifts like this factored into climate change predictions to highlight just how much our natural world might change.

"Living in Hawai'i, I felt grateful that stunning, ephemeral rainbows were a part of my daily life," says land systems scientist Kimberly Carlson, who is now at New York University. "I wondered how climate change might affect such rainbow viewing opportunities."

The forecasts were made by studying tens of thousands of photos of rainbows publicly available on the Flickr photo sharing site. If the location was recorded, these images were referenced against maps of precipitation, cloud cover, and the angle of the Sun.

Next, the team used this real-world data to train a model to predict changes in the global climate in the coming years. They found that areas with smaller populations, at higher elevations, and located at higher latitudes, such as the Tibetan Plateau, will benefit most from the overall increase in rainbow days.

If you want to be in the best places to spot rainbows in the coming years, islands are where you need to go. In particular, islands like Hawai'i will continue to be rainbow hotspots because of their topography.

"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," says atmospheric scientist Steven Businger, from the University of Hawai'i at Mānoa.

The researchers didn't go into too much depth in terms of discussing how such changes in the frequency of rainbows might affect our attitudes or wellbeing – but they did talk about the long shared history we have with rainbows which have infused human culture worldwide, stretching back to ancient times.

And it's worth considering the connection that phenomena such as rainbows (as well as mirages and auroras) establish between humankind and nature. Part of the challenge of successfully tackling the climate crisis is in getting people to care enough about their natural surroundings to want to protect them.

Heavily populated and presumably smoggy areas, along with areas projected to have more dry days and less overall rainfall are expected to see fewer rainbows – a sobering reminder of what we all stand to lose.

The team behind the new study wants to see more of a focus on the parts of our Earth system that cannot be touched or easily quantified – and that might affect our wellbeing and sense of connection in more subtle ways.

"Climate change will generate pervasive changes across all aspects of the human experience on Earth," says Carlson. "Shifts in intangible parts of our environment – such as sound and light – are part of these changes and deserve more attention from researchers."

The research has been published in Global Environment Change.