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

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

Climate change and its evolving effects touch all aspects of what it means to be human, but now there’s a new question about living 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 time of day, the elevation of the earth—that make them possible. Although not critical to sustaining life on earth, rainbows are important enough to the human experience for researchers to determine their value in terms of cultural ecosystem services.

“Rainbows have been part of the lived human experience throughout history and around the world and can also be found in art, literature, music, film, folklore, religion and mythology,” says a team of scientists which set out to understand what is happening. to the rainbow phenomenon as the climate changes. Their peer-reviewed paper was published in the journal Global Environmental Change.

The United States researchers, led by the University of Hawaii, say it is the first time the question has ever been studied. They looked at more than 7,000 verified images of atmospheric rainbows taken between February 2004 and December 2013. The study’s photos came from every corner of the globe except Antarctica.

They then calculated the current probability of a rainbow at locations around the globe, weighing it against expected changes in rainfall, cloud cover and other factors, in order to project future rainbow rates.

For example, snow does not lead to rainbows because it is not wet. But some places in a warming world may see snow fall as rain more often, leading to more frequent sightings of rainbows. In parts of the tropics where rainbows are common and rain is abundant, more dry days may reduce the number of rainbows.

Counts based on 2000, at the turn of the century, put the fewest rainbows in Antarctica and Greenland, and in the arid regions of northwestern China, the Arabian Peninsula, and the Sahara desert. Rainbows were most commonly observed in Kenya, Madagascar, Liberia, and other parts of coastal Africa, as well as in comparable climates of 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, the researchers determined that for many people, the chances of seeing a rainbow will increase by 2100. However, between a quarter and a third of all of land areas of the planet may see decreases in how often one can spot a rainbow.

“In the future with the highest emissions (SSP5 8.5), fallout hotspots 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 can have economic implications for tourism in places where rainbow sightings are common, but overall the researchers say their work highlights aspects of climate change that, like natural sound, affect human well-being but often are overlooked.

“Our results highlight the fact that climate change will alter not only the dynamics of the earth system with clear socio-economic effects, but also parts of the earth system that we cannot touch and that may affect us in more subtle ways,” they conclude. .