What happens to rainbows when the planet’s climate changes?

Rain, cloud cover and other factors make rainbows possible. Climate impacts may mean more of them in some places, less in others.

Climate change and its evolutionary impacts touch every aspect of what it means to be human, but now there’s a new question about life on a changing planet: what’s happening to rainbows?

The ability to see a rainbow depends on changing precipitation rates, cloud cover and other conditions – the angle of the sun and the time of day, the elevation of the terrain – which make them possible. Although not essential to sustaining life on earth, rainbows are important enough to the human experience for researchers to identify their value in terms of cultural ecosystem services.

“Rainbows have been part of the human experience throughout history and around the world and can also be found in arts, literature, music, film, folklore, religion and culture. mythology”, explains a team of scientists who set out to understand what is happening. to the phenomenon of rainbows when the climate changes. Their peer-reviewed work has been published in the journal Global environmental change.

The US researchers, led by the University of Hawaii, say this is the first time the issue has been investigated. They looked at more than 7,000 verified images of atmospheric rainbows taken between February 2004 and December 2013. Photographs for the study came from all corners of the globe except Antarctica.

They then calculated the current likelihood of a rainbow appearing in locations around the planet, measuring it against projected changes in precipitation, cloud cover and other factors to project future rainbow rate.

For example, snow does not produce rainbows because it is not liquid. But some places in a warming world could see snow fall more often as rain, leading to more frequent sightings of rainbows. In areas of the tropics where rainbows are common and there is plenty of rain, drier days could decrease the number of rainbows.

Measurements based on 2000, around the turn of the century, put the lowest number of rainbows in Antarctica and Greenland, and in arid regions of northwest China, the Arabian Peninsula and the desert. of the Sahara. Rainbows have been most commonly seen in Kenya, Madagascar, Liberia, and other parts of coastal Africa, as well as comparable climates in Central and South America. Islands like Hawaii also have quite a few rainbows.

Depending on the climate scenario used and taking into account future population shifts, researchers have determined that for many people the chance of seeing a rainbow will increase by 2100. Yet between a quarter and a third of all global land areas could see a decrease in the frequency with which a rainbow can be sighted.

“Under the highest emissions future (SSP5 8.5), hotspots of decline include the Mediterranean, much of Brazil and northeastern South America, southern Australia and parts of central and southern Africa,” the authors note.

In some cases, this may have economic impacts on tourism in places where rainbow-watching is common, but in general the researchers say their work highlights aspects of climate change that , like natural sound, affect human well-being but are often overlooked.

“Our findings underscore that climate change will not only alter the tangible dynamics of the Earth system with clear socio-economic implications, but also parts of the Earth system that we cannot touch and which may affect us in more subtle ways.” , they conclude.