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Rainbows - February 2023

February – Ephemerality.
Definition: from ephemeral [ɛˈfɛm(ə)rəl, e-fem-er-al] adjective. Lasting for a very short time: "fashions are ephemeral: new ones regularly drive out the old"; "a plant that grows, flowers, and dies in a few days"; "rainbows are inherently ephemeral".

According to science Global Heating & therefore Climate Change will result in more rainbows.  In the map pictured: red (and lighter) coloured areas will generate more rainbows, while blue (and darker) coloured areas will lose days with rainbows.


According to a recent study conducted by scientists (Carlson et al.) at the University of Hawai'i (UH) at Manoa, there will be more opportunities to observe rainbows as a result of Climate Change.  The authors of the study predict that by 2100, there will be net 5% more days with rainbows than there were at the start of the twenty-first century.  The biggest increases in rainbow occurrence will occur in Northern & Southern latitudes, and at very high elevations, where heating is projected to result in less snow and more rain.  The Mediterranean region, for example, is expected to have less rainfall due to climate change, which will result in fewer rainbow days.
Few studies have looked at how climate change might affect the aesthetic qualities of our environment, and no one has attempted to track rainbow occurrences, much less in the context of climate change.
A team made up of UH Manoa students looked over pictures shared on the social media site Flickr to find the answer to this question.  They identified rainbows by sorting through tens of thousands of images from around the globe that were tagged with the word "rainbow."  The researchers then used the georeferenced (photos with coordinates) rainbow photo locations.  Their analysis used maps of precipitation/rainfall, cloud cover, and sun angle to build a rainbow prediction model.  Finally, they used their model to forecast rainbow occurrences in the present and the future over land masses around the world.  
The model concluded that islands are rainbow hotspots.  Islands are the best places to see rainbows, their geography elevates the air during daily sea breezes, causing localised showers that are surrounded by clear skies that let the sunshine through and create magnificent rainbows.

The Hawaiian Islands, recently dubbed the "rainbow capital of the world" are predicted to experience a few more days with rainbows per year.   The authors did not go into detail about how variations in rainbow occurrence can impact people's quality of life.  However, rainbows are beautiful and have played a significant role in human culture throughout history and still.
Climate change will generate pervasive changes across all life on Earth.  Shifts in intangible parts of our environment – such as sound and light – are part of these changes.  In this case, the overall findings are encouraging – it seems people will have more opportunities to see rainbows under Climate Change. 
FYI: February is also, fittingly, the month we celebrate Pride in Aotearoa New Zealand.  As our Southern Hemisphere location means this is the height of summer. Happy Pride 🏳️‍🌈🌈

Carlson, K. M., Mora, C., Xu, J., Setter, R. O., Harangody, M., Franklin, E. C., Kantar, M. B., Lucas, M., Menzo, Z. M., Spirandelli, D., Schanzenbach, D., Courtlandt Warr, C., Wong, A. E., & Businger, S. (2022). Global Rainbow Distribution under current and future climates. Global Environmental Change, 77, 102604.  

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