The city of La Rochelle in the face of climate change
30/04/2025
William ANJOT - Louis BERGEON - Noa DUPUIS - Gwendoline DE SA
Introduction
In its latest report (2023), the IPCC indicates that the global temperature has increased by 1.1°C since the end of the nineteenth century, mainly due to greenhouse gas emissions. According to several scenarios, this increase could reach between +1.4°C (optimistic scenario) and +4.4°C (pessimistic scenario) by 2100.
IPCC studies mainly focus on global or regional scales, but analyses at the local scale are still rare. Yet, understanding the effects of climate change at the local level is essential to better anticipate and manage its specific impacts.
This is why it is important to look at La Rochelle. The city, located by the sea, is particularly vulnerable to rising sea levels. This can lead to beach erosion, saltwater intrusion into groundwater, and more frequent and severe flooding. These risks affect not only the quality of life of the inhabitants, but also the local economy, especially tourism.
La Rochelle is also facing extreme weather events such as storms, heatwaves and torrential rains, which can damage infrastructure and harm public health.
Understanding these local issues makes it possible to adapt public policies and implement specific solutions to protect the environment, populations and the economy. It is therefore crucial to integrate these specificities into climate change resilience strategies.
Problematic
This project aims to carry out an analysis of the past climate of the city of La Rochelle in order to better understand climate changes over time.
Project objectives
In the face of the growing challenges of climate change, it is crucial to adopt concrete and local actions to mitigate its impacts and prepare our communities for a more sustainable future.
Raising awareness among citizens about the impacts of climate change at the local level
This objective aims to inform the population about the concrete consequences of climate change in their immediate environment (floods, heatwaves, loss of biodiversity, etc.).
Finding solutions to reduce climate change risks in the city
This objective involves analyzing the city’s specific vulnerabilities to climate change in order to propose concrete and tailored solutions. For example, this could include rethinking urban planning to better manage rainwater, strengthening green spaces to combat urban heat islands, or developing alert and prevention systems.
Understanding the local impacts of climate change
The study makes it possible to identify the specific consequences of climate change on a given territory (rising temperatures, extreme weather events, water stress, etc.), in order to better anticipate risks and vulnerabilities.
Analysis of the city of La Rochelle
To carry out our analysis and create graphs, we used data from Météo France.
La Rochelle, average temperature,wind speed and rain quantity for each year, from 1980 to 2023
This graph illustrates the annual change in average temperatures. There is a gradual increase over time, characteristic of a global warming phenomenon on a local scale. Between 1980 and 2023, the average temperature increased by 2°C, accompanied by greater irregularity in the appearance of heat peaks, particularly from the 2000s onwards, and more markedly after 2010. This is consistent with global warming trends, which are largely attributed to human activities such as greenhouse gas emissions.
This graph shows the evolution of the average wind speed each year. Like temperature, this speed increases over time, even if the change is slighter. It has increased from 3.8 m/s in 1980 to about 5 m/s in 2023, an increase of 1.2 m/s in 43 years. Even if it is moderate, this increase can have significant effects.
It can cause more soil erosion, disrupt ecosystems and weaken plants. It can also cause damage to buildings and disrupt transportation. On the other hand, this increase can be beneficial for wind energy, provided that the installations are adapted.
In contrast to the other graphs, the trend in rainfall amounts is slightly downward. This reflects a decrease in the average amount of rain in La Rochelle. Since 2010, there has been a trend towards drier years, with several years below 60 mm of average rainfall. The decrease in rainfall in La Rochelle, mainly observed since 2010, is the result of global and local climatic factors.
This leads to environmental consequences, such as water stress for vegetation, increased soil erosion and reduced groundwater recharge. Water resources are becoming more limited, increasing tensions over their management. In addition, the risk of fires is increasing due to the prolonged drought. These changes require adaptations in the management of natural resources and local infrastructure.
Synthesis
These combined trends indicate a shift towards a warmer, windier and drier climate overall in La Rochelle. Such climate changes could have significant implications for the local environment, including water availability, coastal erosion, natural hazard management and adaptation of the agricultural and urban sectors.
It is recommended to continue monitoring local climate variables and to deepen the analysis by integrating other parameters (e.g. relative humidity, extreme events, sunshine) in order to better understand regional climate change dynamics and guide adaptation strategies.
La Rochelle, rain, wind speed and humidity(%) per decade, from the 1980 to 2010
This graph shows the monthly evolution of water withdrawals for the decades 1980, 1990, 2000 and 2010. A marked seasonal distribution is observed, with higher withdrawals at the beginning and end of the year (especially in January and between October and December), and lower values during the summer months, mainly between June and August. This trend is visible in all decades, although the intensity of withdrawals and their regularity vary according to the periods.
The 1990s, for example, show an abnormal peak in April, while the 2010s show more regular but generally moderate rainfall, with a notable increase at the end of the year. This increasing irregularity could indicate increased climate instability, characterized by more intense but less frequent rain events.
This second graph highlights the evolution of average relative humidity throughout the year. A clear trend emerges: humidity is higher in winter and decreases significantly during the summer. However, what is particularly noteworthy is the gradual decline in humidity levels over the decades. In 1980, values remained relatively high throughout the year, while in 2010, they fell significantly during the summer period.
This decrease in humidity could be linked to an increase in average temperatures, a decrease in precipitation, or changes in vegetation cover and evaporation. It can also have consequences for human health, agriculture, and local ecosystems, particularly through increased water stress.
This graph illustrates the variations in average wind speed by month and decade. Unlike the other variables, wind speed remains relatively stable, fluctuating around 4 m/s. However, some fluctuations are worth highlighting. The 2000s recorded higher speeds, particularly between March and August, while the 1980s showed a significant decrease in summer. Wind irregularity appears to have increased slightly in recent decades, which may increase soil evaporation during hot periods and accentuate the effects of drought, in line with the observed decrease in humidity.
Synthesis
To sum up, the climate seems to be changing slowly. Humidity is going down, rainfall is becoming less regular, and wind is slightly more variable. This could be a sign of local climate change, and it’s important to monitor these trends to better adapt in the future.
Heatmap of the evolution of average temperatures in La Rochelle, month by month, from 1980 to 2023
This heatmap shows the evolution of average temperatures in La Rochelle, month by month, from 1980 to 2023.
There is a general trend towards global warming, especially during the winter months. At the beginning of the century, temperatures in January, February or December were often close to 0 °C (in blue). Today, they are closer to 5 to 10 °C (in green or yellow), which reflects much milder winters.
Spring and autumn also show a gradual rise in temperatures, with months such as April, May, September or October becoming increasingly warm.
In summer (June to August), the change is less obvious on this heatmap. Temperatures were already high, so the variation is less visible to the naked eye. However, this warming is most evident when looking at the year-by-year data, which will be better highlighted in the following graph.
Heatmap of the evolution of average annual temperatures in La Rochelle between 1980 and 2023.
This heatmap shows the evolution of average annual temperatures in La Rochelle between 1980 and 2023.
We can see that temperatures are gradually rising. The 1980s and early 1990s were rather blue, which corresponds to cooler temperatures, around 11 to 12 °C. On the other hand, recent years are in red, which shows temperatures around or above 15 °C.
From the 2000s onwards, warming accelerated. Temperature rises are more pronounced and colors change more quickly from blue to red.
La Rochelle, number of days, over or equal to 30°C, per year
This graph illustrates the number of days per year when the daily maximum temperature reached or exceeded 30°C.
In the early decades shown, the number of days above 30°C was relatively modest, fluctuating between 20 and 50 days per year. However, starting in the 2000s, a clear acceleration is visible: the number of hot days has nearly doubled, regularly reaching between 80 and 120 days per year, with some exceptional peaks.
This trend reflects the impact of climate change: high temperatures are becoming increasingly frequent, which has significant consequences for the environment, agriculture, and many other sectors.
Reduction and Adaptation Strategies
The climate is changing in La Rochelle, and this causes real problems. To deal with it, the city needs to act in two ways: reduce what causes climate change, and adapt to its effects.
To reduce the causes, we must pollute less. For example, people can use bikes, buses, or shared cars more often. Buildings should be renovated to use less energy, and electricity can come from the sun or wind. Reducing waste and eating more local food also helps protect the environment.
But since climate change is already happening, we also need to adapt. That means planting more trees to cool the city, protecting the coast from floods, and setting up alerts for heatwaves or storms. Farmers also need to change how they work to deal with dry periods. Everyone must help: residents, businesses, and the city government. Together, we can build a better future.
Conclusion
Since 1980, the climate in La Rochelle has changed. Temperatures have gone up, the air is drier, there is less rain, and there are more very hot days. These local changes are part of global warming.
These changes affect daily life : health, water, nature, farming, and tourism. To be ready for the future, we must keep watching the climate, understanding how it changes, and adapting the city. This is important to protect people and the environment.