Researchers have found that high temperatures lead to a significant and immediate reduction in politicians' language complexity, after analyzing the language used in seven million parliamentary speeches around the world.

The paper was published on June 13 in the journal Interdisciplinary Science, a subsidiary of Cell Press.

The collection represents more than 28,000 people in eight different countries over several decades.

Researchers from the Max Planck Institute for Demographic Research in Germany and Aarhus University in Denmark explored connections between the language in those speeches and precise daily temperatures and weather. They used a modeling strategy that leveraged the seemingly random variations in daily temperatures to analyze their impact. 

The results suggest that rising temperatures may impact our cognitive abilities with real and immediate consequences, the researchers say.

The researchers say this approach allowed them to isolate the effect of temperature on the complexity of a person's speech. The results of their analysis were surprising: hot weather reduced the complexity of speech, while cold weather did not have the same effect. "This suggests that even in professional environments that require precise and complex language, heat can have a negative impact on cognitive function," said Tobias Wiedemann, a researcher at Aarhus University.

The study also showcases an innovative use of computational methods, including automated text analysis combined with global meteorological data, to assess the broader impacts of climate change on human health and performance.