What if the extraordinary heatwave of 2003 became the ordinary of tomorrow? what the study modeled of the climate risk assessment start-up Callendar on Tuesday, September 3. While the Paris Agreement aims to keep the global temperature below 2 degrees Celsius, a new reference scenario has been adopted by the French government in 2023 as part of the 3rd national plan for adaptation to climate change: a warming of 4 degrees in metropolitan France compared to the period 1900-1930. But such an upheaval could well have irreparable consequences on society.
Heat waves 2 to 5 times more severe
Starting with increasingly frequent heatwaves. It is no secret that the last two decades have been marked by a succession of heatwaves of unprecedented intensity. In France, one of them particularly left its mark: the heatwave of August 2003. While this exceptional episode continues to be unprecedented today, it could tend to become commonplace. Based on the scenario of a 4-degree warming in metropolitan France, the study states that heatwaves comparable to that of 2003 could occur several times per decade. In some cities such as Montpellier, Marseille and Nice, these heatwaves would occur 9 and 8 times per decade respectively, or almost every year.
Cities affected by heat waves.
© / Screenshot – Callendar,
And beyond seeing their frequency increase, heat waves will also see their duration lengthen. Among other things, some episodes could extend over more than two months, lastingly impacting society. As for the severity of the heatwave, it could, depending on the region, be two to five times more intense than that of 2003.
A health, social and financial cost
Models that question our ability to adapt. In our recent history, with a 48% increase in the number of deaths per day in August 2003, this peak in excess mortality remains without equivalent. The Covid-19 crisis has caused a 28% increase in the number of deaths. But at present, how resilient would we be in the face of such a heatwave? According to the study conducted by Callendar, with a warming of four degrees, the ability to cope with such heat waves without a prohibitive economic and human cost is not guaranteed. Currently going through a crisis, health systems should therefore be prepared to overcome the increase in heat-related illnesses.
But health and social costs will not be the only consequences of this phenomenon. Financing such an adaptation would also be significant. Let’s take the example of air conditioning. In the scenario studied, such frequent and severe heatwaves would lead to a sharp increase in the use of air conditioning. Like Japan or the United States, France would be forced to fully adopt it. A finding that is as worrying for finances as it is for the environment. Consequently, this excessive and unusual use would lead to an increase in demand for electricity and thus a change in its seasonality, certainly requiring an upheaval of the electricity system, starting with the distribution networks. A much less costly solution than adapting to the consequences of a four-degree warming therefore seems to be necessary: reducing carbon dioxide emissions.