The heatwave that Europe is experiencing today does not just affect the daily life of vacationists. It is also a reminder of the climate change we face and takes us back to the influence of climates on our civilizations, which Aristotle, Montesquieu, and later Emmanuel le Roy Ladurie, with others, framed the theory.

Very recently in a research publication ( « Quantifying the Influence of Climate on Human Conflict », Solomon M. Hsiang, Marshall Burke, and Edward Miguel in Sciencexpress, published online 1 August 2013) pointed out to me by Eric Chaney, the effects of climatic changes: based on an analysis of 60 studies from 190 researchers in various disciplines and from different countries on conflicts of various sizes (interpersonal conflicts, conflicts within and between countries) in various parts of the world and on different dates (from 10,000 B.C.E. to the present day), they show that the risk of conflicts rises when there is a change in climate toward warmer temperatures or more extreme rainfall. And that wars and interpersonal violence, responsible today for half a million to a million deaths every year, will intensify considerably in the future, under the impact of new climatic disruptions.

First domestic violence rises across all regions of the globe when there is a change in climate toward warmer temperatures, and also rises among poorer farmers when there is a change in climate toward more extreme rainfall, cutting into a farmer’s profits.

Then intergroup conflict rises with climatic disruptions, especially in low-income settings. Civil wars are linked to climate extremes with excessive heat or rapid fall in temperature, or drought. A high climatic stress can make institutions vulnerable and can result in important and disruptive changes (leaders being deposed by force, new methods of operation in land-use planning and tenure, and even the collapse of communities, empires or civilizations). There are countless examples of this: in Europe, key periods marking an instability coincided with episodes abnormally cold; in India, riots between India’s Hindu and Muslim communities rose with the extreme precipitation; in China, the fall of the Tang dynasty (as in the case for the Mayan civilization in Mexico) occurred at the turn of the 10th century, as precipitation was altered by the Pacific Ocean; lastly, the fall of the Yuan Dynasty, in 1368, occurred at the same time as that of Angkor which experienced the same climatic disruptions.

This is attributable to: changes in global climatic conditions that can cause impairment of cognitive abilities or The theory of mind (ToM) impairment, or other physiological phenomena; an economic disruption, lower tax revenues; a loss of legitimacy of public institutions; an increase in food prices and population movements.

But there is much more: on the basis of these studies, their authors show that, each one standard deviation (1σ) change in the climate, (measure of the dispersion of a variable around the mean) toward warmer average temperatures or more extreme rainfall, meant an increase by 4 percent in the frequency of crime and by 14 percent in the frequency of intergroup conflicts.

However, by 2050, the dispersion of climate change should be higher than 2σ in relation to the historical standard deviation (measured by the mean dispersion of temperatures between 1950 and 2008). It should even exceed 4σ in tropical regions.

We can therefore expect very sharp increases in crime and wars, within and between countries, particularly in subtropical Africa, India, south of China, Indonesia, Mexico and Brazil.

And one does not need to be a genius in order to measure their massive impacts. Will all these converging signs of threats in the future finally be taken seriously?