Scientists have earlier reported about the impact that human activities are having on Earth's climate. A new study suggests that there may also be a connection between extreme temperatures brought by climate change and the number of males born compared to the number of females. The gap between male and female babies may be closing because of the climate change.

A group of Japanese and Danish researchers examined two extreme climate situations in Japan, the exceptionally hot summer of 2010 and the country's very cold and snowy winter of 2011.

"The recent temperature fluctuations in Japan seem to be linked to lower male: female sex ratio of newborn infants, partly via increased male fetal deaths. Male conception seems to be especially vulnerable to external stress factors, including climate changes", said the authors in the September issue of Fertility & Sterility, a journal of the American Society for Reproductive Medicine.

The sex ratio of newborn is fairly steady worldwide with little higher number of males being born compared to females. The scientists led by Misao Fukuda of M&K Health Institute in Ako, Japan, were eager to know about how climate change might impact the ratio.

Over the last century, average temperatures in Japan have increased by more than one degree Celsius (1.8 Fahrenheit).

The birth records provided by Vital Statistics of Japan and temperature data obtained from the Japan Meteorological Agency were studied by Fukada and his team.

Japan recorded 90,000 newborn and around 1,000 fetal deaths every month between 1968 and 2012. Mean temperature between 1968 and 2012 in Japan was 14.1 degrees Celsius.

Researchers found statistically significant rise in the fetal death rate in September 2010. They also found a major decline in the sex ratio in June 2011.

Since 1986, Japan faced a very cold period, with the most extreme snowfall in January 2011. The team found a decrease in the difference between male and female births nine months later in October 2011, compared to surrounding years 2008-2012. This study is the first to find correlation between the ratio of male and female births and climate change.