New research reveals that extreme heat is literally changing the human population's sex ratio — but for two completely different reasons. A massive study of 5 million births in sub-Saharan Africa and India, published recently in PNAS, shows that hot days during pregnancy result in significantly fewer male births.

In sub-Saharan Africa, the cause is biological. Heat stress during the first trimester increases the rate of miscarriage. Because male fetuses are biologically more fragile, they are disproportionately lost to maternal heat stress.

In India, however, the cause is behavioral. Heat waves during the second trimester disrupt access to medical services and financial resources, inadvertently reducing the rate of sex-selective abortions (which typically target girls).

Co-authored by researchers including Portland State University's Joshua Wilde, the study highlights how climate change is quietly acting as both a biological filter and a disruptor of human behavior.

About The Article: Climate change is increasing the frequency and intensity of heat waves and the exposure of pregnant individuals to extreme heat. This article summarizes current evidence about risks to maternal health from ambient heat (hot weather, high indoor temperatures, and occupational exposures) and how these risks can be managed.

Forecasters could give India weeks of advance warning before moist heatwaves strike

The progressive rise in temperatures poses a growing threat to the staging of summer sporting events in Europe and, more specifically, to the Tour de France, due to the increasing risk of heat stress for athletes. This is one of the conclusions of a study published in Scientific Reports, which analysed climate data associated with more than 50 editions of the French race. The progressive rise in temperatures poses a growing threat to the staging of summer sporting events in Europe and, more specifically, to the Tour de France, due to the increasing risk of heat stress for athletes. This is one of the conclusions of a study published in Scientific Reports, which analysed climate data associated with more than 50 editions of the French race.

A new study reveals that heat uptake fluctuations in the Aegean Sea during August provide a powerful new tool for predicting Eastern Mediterranean winter rainfall. Researchers developed the Aegean Sea Heat Uptake Anomaly (AQA) index, showing that when the sea releases more heat in late summer, the following winter tends to bring more frequent and persistent “Cyprus Low” storm systems across the Eastern Mediterranean. The regional index captures a substantial share of year-to-year rainfall variability and significantly improves seasonal forecasting skill compared to traditional global climate indicators such as ENSO and the North Atlantic Oscillation (NAO). By identifying a localized ocean signal with strong predictive power, the study marks a major advance in Mediterranean seasonal rainfall forecasting.