Dear Cyril,

It's a perfectly sensible question if it's asked the other way around, which is what you intended I'm quite sure!

"Can the global rise of infertility in women be attributed to climate change?" There, that's better.

You might delete this question, and set up a new one.

Christopher NOCK

Hi Cyril, I think this piece of contribution from Alan Barreca published on World Economic Forum in collaboration with The Conversation, could be somewhat useful:

How does climate change affect fertility?

30 Nov 2015

Alan Barreca

Associate Professor, Tulane University

This article is published in collaboration with The Conversation.

Policymakers are tasked with addressing climate change in the face of uncertainty: the 2013 IPCC report projects average global temperatures will increase by anywhere from 5 to 10 degrees Fahrenheit (3 to 6 degrees Celsius) in the coming century if we continue on our path of greenhouse gas emissions.

The uncertainty is compounded by the fact that the consequences of any temperature change are unknown, including how something as basic as human fertility might be affected.

Understanding how climate change will affect fertility is an important economic concern. According to World Bank estimates, in the United States and many European countries, a woman has fewer than two children on average by the end of her reproductive life.

These “below-replacement” birth rates are already putting stress on programs that are funded by the working-age population, like Social Security. Any additional decline in births due to climate change could only make this worse.

Links between temperature and fertility:

Global warming might directly affect fertility in two key ways.

First, hot weather could affect sexual behavior. After all, physically demanding activities are more difficult at high temperatures.

Second, temperature could negatively influence reproductive health factors such as sperm motility and menstruation. There are some pretty compelling experimental studies on mammals to support this possibility.

It is these two potential links that led us to hypothesize that global warming might be a threat to human reproduction, something that had yet to be thoroughly investigated by scientists and policymakers.

Our recent NBER study, “Maybe Next Month? Temperature Shocks, Climate Change, and Dynamic Adjustments in Birth Rates,” tests this hypothesis using data on temperature and birth rates from the United States from 1931 to 2010.

The ‘natural’ experiment:

Up until recently, there was little consensus regarding temperature’s effect on fertility due to the dearth of experimental evidence. We cannot quantify climate’s role by simply comparing birth rates in “hot” and “cold” places – Louisiana is different from New York in more ways than just weather.

To isolate the effects of temperature, our study relies on a natural experiment: weather fluctuations from year to year in each US state are effectively random. We tested to see if births in Louisiana changed after an unusually hot August.

Our study also controls for many social and economic factors that are changing over time, including economic opportunities for women and access to birth control. While we don’t discount their importance, we were interested in quantifying temperature’s effect above and beyond these other factors.

Hot days and conception chances:

We focus on the effects of “hot days,” which we define as days where the average daily temperature is above 80F (27C). Because we averaged the minimum and maximum temperature, the daytime temperature on these days is usually above 90F (32C), which most of us would find to be very hot.

The core finding is that hot days lead to a reduction in birth rates eight to 10 months later. The effect size is largest at nine months: on average, each hot day reduces birth rates nine months later by 0.4% or about 1,100 births. Importantly, the data also show that air conditioning played a major role in minimizing the impact that hot days pose for fertility.

Our study also explores whether the initial decline in birth rates is offset by an increase in the following months. The data show only a partial (32%) “rebound” in birth rates in the three months after the initial decline, possibly due to lingering health effects, work constraints or the natural decline in reproductive health with age. This suggests that these shocks could reduce the number of children a woman has over the course of her reproductive life – a growing concern for the United States and many countries.

[FIGURE]151130-climate change fertility rates birth rates hot days conv chart

Figure illustrates the estimated change in monthly birth rates from each additional hot day. The decline in births occurs eight to 10 months after the hot day, and is then followed by a rebound in months 11 to 13.

As one limitation of our study, we tested for a rebound in births for only up to one year after the initial decline, so there could be some longer-term rebound for which we do not account.

While sexual behavior could certainly be influenced by hot weather, we present some novel evidence to suggest that reproductive health is especially vulnerable. If the story were just about temperature making sex uncomfortable, then we would only see a fall in births eight to nine months later. Instead, we find that birth rates also fall 10 months later, suggesting that hot days have lasting health effects. However, more research is needed to definitively verify this hypothesis.

Fertility costs of climate change:

Currently, the United States experiences nearly 30 hot days per year. A prominent global circulation model projects that the United States will experience a tripling of the number of hot days to about 90 by the end of the 21st century.

We project that this warming will cause the number of births to fall by about 107,000 per year by then. There will also be more summer births, due to the rebound, which will expose pregnancies to considerably hotter days during the third trimester and will threaten infant health.

As a caveat, these projections focus exclusively on the fertility cost of heat stress and do not offer insight into the costs of natural disasters or other major social changes resulting from climate change.

Should nothing be done to mitigate climate change, our study indicates that air conditioning can lower the fertility costs. But, we caution that in order to avoid exacerbating climate change, any increase in energy use for air conditioning must be offset with decreases in emissions in other parts of the economy.

While our study offers lessons from the United States, it is uncertain how global warming might impact fertility elsewhere in the world.

Many developing countries, like India, already experience hotter climates than the United States. As a result, these developing countries are more likely to feel the effects of climate change, which could include worse fertility outcomes.

Unfortunately, this is one more area where the costs of climate change are uncertain.

Publication does not imply endorsement of views by the World Economic Forum.

Author: Alan Barreca is an Associate Professor of Economics at Tulane University.

Melanie Guidi is an Assistant Professor of Economics at the University of Central Florida.

Olivier Deschenes is an Associate Professor at the University of California, Santa Barbara

no

If you see a correlation between climate change and female infertility (or perhaps better expressed as lower reproductive rates), then the connection is equally valid in both directions, i.e., lowered fertility causes climate change, and climate change causes lower fertility.

Now see if you have a noticeable increase in fertility during the Little Ice Age (when temperatures fell) as a check on your conclusions.

Also, do fertility rates fall equally in all countries at the same time? Are they falling fastest in Alaska (where there is a big impact of climate change), but less so in, say, Mississippi? (There should be good data in these places.) What about globally.

I think it won't take long to find that there may be an external driver, like economic prosperity, that is driving both. One hates to say it, but check out a stats textbook on 'Correlation.'

@Bill Hazelton thank you, I found this very helpful.

You're very welcome!

The answer to your question is "No". In fact, polycystic ovary syndrome (PCOS) and obesity are the main reasons behind global rise of infertility in women.

Yes because, climate change has made nutrition a problem, has resulted in pollution and this has an impact on the fertility of people.

I fhink yes

I fhink yes