In the icy tundra of Siberia, people speak in tightly wound sounds with consonants packed like frozen gravel. A few thousand miles to the south, under the humid canopy of Papua New Guinea, speech flows much differently: vowels swell and ripple while syllables spread open like sun-warmed petals. These are not just cultural quirks. According to some scientists, they may reflect a complex interplay between language and the climate.

A team of linguists analyzed the basic vocabularies of more than 5,000 languages and found a striking pattern: languages that developed in warmer climates tend to sound more resonant, what linguists call more “sonorous.” That means more vowels, more flowing sounds, more openness in the mouth. In short, these languages sound louder. Meanwhile, languages born in colder places are more clipped, more congested with consonants.

The differences can even be pinned to the very physics of speech. Sound travels through air. And air, as it turns out, behaves differently when it’s warm.

“Generally speaking, languages in warmer regions are louder than those in colder regions,” said Dr. Søren Wichmann, a linguist at Kiel University and co-author of the study that appeared in 2023 in the journal PNAS Nexus.

Temperature and the Shape of Sound

“Sonority” is a measure that blends loudness, resonance, and openness of speech sounds. Words filled with vowels — like open or mouth — are more sonorous than those packed with hissing consonants, like lips or crisp. Sonorants, such as vowels and nasal sounds, travel farther and resist distortion better than obstruents — harder sounds like k, t, or s.

Using a massive linguistic dataset known as the ASJP (Automated Similarity Judgment Program), the researchers computed a “mean sonority index” for each language and mapped them onto global climate data. Their results revealed a compelling trend: languages near the equator, especially in Oceania and Africa, had the highest sonority values. Those in colder regions, like the Salish languages of North America’s northwest coast, exhibited the lowest.

But why?

One explanation is physiological. Cold air is dry, and that dryness irritates the vocal cords, making it harder to produce voiced sounds like vowels. “Cold air poses a challenge to the production of voiced sounds, which require vibration of the vocal cords,” said Dr. Wichmann.

Another explanation comes from acoustics. Warm air absorbs high-frequency sounds more than cool air does, potentially muting consonants. This could have encouraged languages in hot climates to lean toward lower-frequency, resonant sounds that better resist distortion over distance.

Perhaps this is the biggest takeaway: the physical properties of air influence how easy it is to produce and hear speech. But as the climate warms across the world, does that mean that our language will increasingly become louder? That’s an obvious conclusion that the authors seem to ascribe to.

“Our findings suggest that lower temperatures, over the course of many centuries, lead to decreased sonority,” the authors write.

Climate and the Evolution of Language

This isn’t the first time scientists have tried to link language structure to environmental conditions, but it may be the most comprehensive attempt to date. Previous studies looked at fewer than 100 languages. This study drew on nearly three-quarters of the world’s documented languages and traced patterns over centuries.

Yet the pattern only emerges across broad sweeps of geography and time. When the researchers zoomed in on individual language families — like Indo-European or Bantu — they found no consistent relationship between sonority and temperature. In fact, some warm-climate languages in Central America and Southeast Asia still scored low on sonority. Some of the languages included in the analysis only sampled 40 words, although this is partly because some very rare languages in the dataset lack additional words. In other words, this is not a perfect association between temperature and sonority.

Without weighting words by how often they’re used, the picture of a language’s “sound” remains fuzzy. A rare, vowel-rich word shouldn’t carry the same analytical weight as a common, clipped one. Still, despite these limitations, the study is compelling and invites us to imagine how our language might sound centuries from now.

That’s because language does not change quickly. The absence of a climate-sonority correlation within language families suggests the shift in sound patterns unfolds slowly, over millennia.

Environmental History and Language

The researchers argue that sonority may reflect the environment in which a language originally evolved, even if its speakers later moved elsewhere.

“If languages adapt to their environment in a slow process lasting thousands of years, then they carry some clues about the environment of their predecessor languages,” said Wichmann.

That perspective has enormous implications. It hints that by studying the sounds of ancient or isolated languages, we may be able to glimpse long-lost climates and migration paths. It also challenges long-held assumptions in linguistics that languages evolve independently of their surroundings.

“For a long time, research assumed that linguistic structures are self-contained and are not influenced in any way by the social or natural environment,” Wichmann said. “More recent studies, including ours, are beginning to question this.”

The authors see their findings as consistent with the Acoustic Adaptation Hypothesis, a theory that animals, including humans, evolve vocalizations best suited to their habitats. Birds sing differently in forests than they do in open fields. Why not humans?

Lingering Questions

Despite its breadth, the study leaves room for debate. For instance, it’s still unclear whether cold climates drive sonority down more forcefully than warm climates push it up. The data suggest cold air has a stronger muting effect, yet that too requires more targeted research.

There’s also the issue of word length. Longer words often contain more vowels, making them more sonorous by default. The team did find a modest link between word length and sonority, suggesting that intrinsic features of languages, like how they build words, may also shape their sonic profile.

Ultimately, language evolution is a tangle of influences. Phoneme inventories, syllable structure, climate, culture, and even how parents talk to babies all play a role.

Yet this study delivers an intriguing message: the way we speak is not just a product of history and identity, but of air itself.