You might guess that art buyers at auction make their decisions about how much to bid based on factors like rarity, quality, and personal taste.

But might they also be affected by other less expected variables, like the weather? The short answer is: Yes.

Global warming may be bad not only for polar bears and other members of the animal kingdom, but also for auctioneers, according to data from Artnet Analytics.

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We crunched the data on tens of thousands of auction results over the last 15 years in New York City, where Christie’s, Sotheby’s, and Phillips all have their flagship locations.

We cross-checked that information against data on temperatures in Central Park on sale days (from the National Oceanic and Atmospheric Administration) and stats on how sunny it was on sale days (from the National Solar Radiation Database). What we found may surprise you.

1. Sunny days equal better results
This one might not seem so unexpected. Sunny weather makes you happier, and that leads to better sale results. While we know that weather impacts consumption in the retail industry, as demonstrated by a study done by Summers and Hebert in 2001[1], sunlight significantly impacts mood. Now, if the houses can order up better weather on sale days, their problems will be solved.

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2. Global warming will cost the industry
Colder weather, on the whole, induces more aggression and competitive behavior (see, eg, Howarth & Hoffman, 1984[2]). Similar results have been demonstrated in the stock market by Cao and Wei (2005)[3]. Lower temperatures tend, on average, to generate more aggression while hotter weather can lead to apathy. So global warming spells trouble.

The intergovernmental Panel on Climate Change forecasts an increase of up to 10 degrees over the next century. According to our model, in that worst-case scenario, the auction market would take a hit of some $145 million in annual revenue.

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3. Higher temperatures mean fewer lots sold
As shown in this graph, higher temperature correlates directly with fewer lots finding buyers. 40-degree days, on average, result in better sell-through rates with over 78 percent of works on offer being bought. When it gets up to 90 degrees, though, that number drops to about 75 percent.

4. Best combination: a sunny day in the fall
November sales show a far higher number of artworks coming to auction—more than 50 percent of the whole year’s offerings, in fact. So it’s as though auction houses and sellers had intuited that since November is cooler, buyers will be more aggressive. Why not sell during January, then? Not enough sunlight! A sunny day in November, then, is the sweet spot[4].

5. Phillips might actually benefit from climate change
Christie’s and Sotheby’s are the top dogs in the auction field, but Phillips contemporary art day sales reap unexpected bonuses from higher temperatures. As temperatures positively influence testosterone responses in men (as per a study by Anderson et al in 2002[5]), the appeal for more risky and volatile art may attract individuals with a taste for risky acquisitions. Our theory: Because the younger artists Phillips is known for selling may attract more risk-taking buyers, and because warmer days increase testosterone levels in men, the soaring thermometer readings might just mean soaring sale tallies.

Research by Fabian Bocart for artnet Analytics.

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[1] Summers, T. A., & Hebert, P. R. (2001). Shedding some light on store atmospherics: influence of illumination on consumer behavior. Journal of business research, 54(2), 145-150.

[2] Howarth, E., & Hoffman, M. S. (1984). A multidimensional approach to the relationship between mood and weather. British Journal of Psychology,75(1), 15-23.

[3] Cao, M., & Wei, J. (2005). Stock market returns: A note on temperature anomaly. Journal of Banking & Finance, 29(6), 1559-1573.

[4] De Silva, D. G., Pownall, R. A., & Wolk, L. (2012). Does the sun ‘shine’on art prices?. Journal of Economic Behavior & Organization, 82(1), 167-178.

[5] Andersson, A. M., Carlsen, E., Petersen, J. H., & Skakkebæk, N. E. (2003). Variation in levels of serum inhibin B, testosterone, estradiol, luteinizing hormone, follicle-stimulating hormone, and sex hormone-binding globulin in monthly samples from healthy men during a 17-month period: possible effects of seasons. The Journal of Clinical Endocrinology & Metabolism,88(2), 932-937.