2023-08-08 11:55:16
Date August 8, 2023 Add Article added Download PDF Share
According to a study carried out by economists from the Allianz group, preliminary data relating to the heat waves that have hit Europe, China and the United States since the beginning of the year indicate that “the toll of the heat wave is close of 0.6 point of GDP growth for 2023”.
This cost is calculated from two models dealing with the decline in labor productivity due to extreme temperatures, developed in scientific papers published in 2021. Due to the high number of days (47) in which temperatures were above 32°C between May and August, China would have lost 1.3 points of GDP since the beginning of the year. Although the models used are proven, the authors recognize the limits of these estimates, in particular the fact that daily averages by country were used rather than data by grid cell as well as the failure to take into account certain vectors of impact, such as agricultural productivity.
It can legitimately be assumed that the economic consequences of heat waves are underestimated when agricultural yields are excluded. A study published in 2017 indicated that for each day that temperatures were above 30°C, corn and soybean crop yields under rainfed conditions decreased by up to 6% in the United States. The increase in duration, intensity and frequency of heat waves observed in recent decades indicates that these numbers might be higher today.
The broad definition of what constitutes a heat wave used in the article – any day when the national average was above 32°C during a given period – disregards the local specificities of calculation and might also underestimate the economic impact of extreme heat.
According to the World Meteorological Organization, “there is currently no agreed international system or protocol for the naming or coordination of the naming of heat wave episodes. […] this is broadly defined as a period of statistically unusual warm weather that persists for a number of days and nights.” In France, this is measured once morest the national thermal indicator, which corresponds to an average of daily measurements of mean air temperature. For a heat wave to be declared, this indicator must be greater than or equal to 25.3°C for one day and greater than or equal to 23.4°C for at least 3 days. The U.S. Environmental Agency defines a heat wave as “a period of two or more consecutive days during which the daily minimum apparent temperature (the actual temperature corrected for humidity) in a given city exceeds the 85th percentile historic July and August temperatures (1981-2010) for this city”.
In a report published in 2019, the International Labor Organization predicted that “heat stress is expected to reduce total working hours worldwide by 2.2% and global GDP by $2.4 trillion in 2030”. . If heat stress – which describes a situation “where it is too difficult to work, or at least too difficult to work at normal intensity” – is only a marginal phenomenon in Europe which occurs above all during the summer, it is present all year round in certain regions of the world, particularly in South and South-East Asia and in West Africa.
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