Many would probably be surprised to learn that a paper on climate classification has been referenced 2.8 million times on Wikipedia. The authors of the paper certainly were, as WIRED reported.

According to a recent analysis by The Wikimedia Foundation, which oversees Wikipedia, a paper titled "Updated world map of the Köppen-Geiger climate classification" is by far the most cited source on the site, making its authors something like Wikipedia rock stars. To put that number in perspective, it's slightly less than the number of followers that rapper Cardi B has on Twitter.

While climate classification might not be the sexiest topic, it's incredibly useful across a number of fields, "since climate can affect everything from biology to sociology," as WIRED noted.

Penned by three Australian researchers, the academic paper updates an older version of the Köppen-Geiger climate classification system, which was originally conceived in 1884 by Russian-German climatologist Wladimir Köppen and updated in the 1950s by German climatologist Rudolf Geiger.

The Australian researchers—Brian Finlayson, Thomas McMahon, and Murray Peel—updated the map that accompanies the classification system yet again in 2007. The map's use has been widespread, with Lonely Planet reportedly using it to share general weather information about the various destinations it provides travel guides for.

Peel, M. C., Finlayson, B. L., and McMahon, T. A., Wikipedia // CC BY-SA 4.0

Finlayson, a retired geography professor from the University of Melbourne, was shocked to learn how frequently their map is referenced. "Those numbers blew me away," Finlayson told WIRED. "None of us had any idea about this. We didn't know Wikipedia collected this information or anything about it."

The Wikimedia Foundation arrived at this figure by analyzing the data of every citation in all of Wikipedia's 297 languages. The only stipulation was that the citations had to be paired with an identifier (for example, "DOI" for a scholarly paper, or "ISBN" for a book edition), but even after narrowing it down, they ended up with nearly 15.7 million records.

All of the top 10 sources by citation are reference books or scientific articles. Trailing far behind the updated Köppen-Geiger map in second place, with 21,350 citations, is some light reading on the "Prediction of Hydrophobic (Lipophilic) Properties of Small Organic Molecules Using Fragment Methods." "Galaxies and How to Observe Them," "A Concise History of Romania," and the California Academy of Sciences' "Catalog of Fishes" also make the top 10.

[h/t WIRED]