Media  Global Economy  2023.04.19

"In Vietnam, global warming has a negative impact on students' math test scores"

Le Monde on April 14th, 2023

This article was initially published in French in Le Monde newspaper on 14. April 2023, as part of a series of monthly columns on Asian economies. The original article can be found here:

Southeast Asia

Column by Sébastien Lechevalier, Professor at Ecole des Hautes Etudes en Sciences Sociales (EHESS, Paris), Senior Researcher at Maison franco-japonaise (UMIFRE 19, Tokyo) and at the Canon Institute for Global Studies (CIGS, Tokyo).

In his column, researcher Sébastien Lechevalier reports the results of an investigation by a Vietnamese economist on the link between rising temperatures, which would reduce cerebral blood flow, and the solving of mathematical problems.

Column. Examples of the consequences of climate change on our societies are numerous and concern various fields, but relatively few studies have analyzed the consequences on education and cognitive abilities. However, a Vietnamese economist, Tien Manh Vu, was able to show that the increase in temperature has a significant negative impact on students' results in mathematics tests (« Effects of heat on mathematics test performance in Vietnam », Asian Economic Journal, 2022).

It confirms the results of previous studies, but is one of the first to focus on a developing country. This is particularly important for developing countries, which tend to be in the hottest regions, with poor people more exposed to the heat and less able to reduce the individual consequences of global warming. This is also critical for Vietnam, which invests heavily in education.

The main mechanism determining individual performance is related to heat tolerance. In this case, mathematical problem solving depends on brain function located in an area of the prefrontal cortex and neural circuits. In addition, high temperature would reduce cerebral blood flow, and therefore the efficiency of test performance.

300,000 students

Conducting this type of research poses several methodological challenges and requires high-quality data. This article addresses both of these challenges. The author cross-references the results of the July 2009 Vietnamese university entrance exam mathematics tests with very precise data collected by an American meteorological agency. The geolocation of these data allows us to link them to the test locations and to nearly 300,000 students who took the test.

Moreover, the author takes several methodological precautions to measure the desired effect as well as possible, and acknowledges certain limitations of his study. For example, the data are old, from a time when global warming was not felt as strongly as today.

In fact, the paper only compares the effects of heat at one point in time between regions with different temperatures, but does not directly measure the impact of rising temperatures in a given location: during the test period, in July 2009, temperatures averaged over 28°C, compared to about 25.5°C between 1950 and 2009. Finally, the effect of humidity, which further increases the impact of heat, is not taken into account.

Rural people more vulnerable

In the end, the results are clear: a one-degree increase in temperature leads to a modest but significant decrease in average math test scores. The results are mostly independent of the students' region of origin, which contradicts the myth that individuals living in warmer regions are better adapted to climatic conditions. In addition, the impact of heat waves creates inequalities: women and rural residents are the most vulnerable.

Global warming has already begun to have a significant negative impact on our cognitive abilities, which may offset the positive impact of investing in education. Additional spending on equipment such as air conditioning can create other negative externalities, for example for the climate.

In France, in recent years, exams have already been postponed due to heat waves and unsuitable examination venues. Perhaps we will have to radically change the school calendar and test dates to adapt to this other deleterious effect of global warming.