Between 1960 and 1990, there were twice as many hot days in the Congo Basin
Evidence of climate change salvaged from paper archives
Brussels, 12 October 2026 - An analysis of recently digitised and transcribed historical weather data – which until recently was only available as handwritten archive documents in the Democratic Republic of the Congo and in Belgium – shows that a consistent warming trend can be observed across the entire Congo Basin
New research led by the Vrije Universiteit Brussel (VUB), published today in the journal *Earth System Dynamics*, demonstrates – based on historical weather data from the Democratic Republic of the Congo (DRC) – that a clear warming signal has been observable in the Congo Basin since the 1960s. The data comes from the paper archives of the Institut National pour l’Etude et la Recherche Agronomiques (INERA) in Yangambi, DRC, and the Belgian State Archives.
During two field campaigns in 2023, Derrick Muheki, a researcher at the VUB and lead author of the study, in collaboration with staff from INERA and Ghent University (UGent), photographed more than 9,000 handwritten monthly sheets of weather observations, which had been recorded at 37 stations across the DRC. Using MeteoSaver, an award-winning open-source programme developed by Muheki at the VUB, in collaboration with the team at the UGent Centre for Digital Humanities, the research team automatically converted these observations into digital spreadsheets, which they used to chart trends in temperature and precipitation in the Congo Basin. The resulting database contains over a million daily (and sometimes more frequent than daily) weather observations which, together with previously salvaged data, form one of the largest climate datasets for the Congo Basin – a region that had not been studied until now.
Based on an analysis of this new database, the authors describe, for the first time, the trends in heat extremes in the Congo Basin since the 1960s:
- Daily maximum, minimum and average temperatures rose by tenths of a degree per decade between 1961 and 1990. Over the period 1961–1990, maximum temperatures rose by approximately 0.7 °C, minimum temperatures by 0.3 °C and average temperatures by 0.5 °C.
- This warming of the Congo Basin has continued into the 2000s, as shown by data from weather stations with longer time series.
- Each successive decade shows an increase in the number of hot days per year, with hot days becoming hotter, whilst the number of cold days is decreasing, in line with global trends. On average ,the number of hot days per year almost doubled between the 1960s and the 1980s, confirming the undeniable warming trend in the region.
Furthermore, based on an analysis of historical precipitation data from three weather stations, the authors note that the number of heavy rainfall events at two of these stations doubled in the 1980s compared with the 1960s. This observed increase in the frequency and intensity of extreme weather events in the DRC is consistent with global trends, which are linked to rising global temperatures resulting from continued emissions from fossil fuels.
Historical climate data on Central Africa have been extremely scarce until now, and this open-access database provides new evidence to outline the climate context for a region that is currently heavily affected by climate change. The database also provides key information for evaluating and improving climate models in the region and underlines the importance of efforts to preserve data worldwide.
“When I saw how vulnerable these paper archives were during my visit to INERA, I realised just how urgent the work to preserve data is. Just a few months before my visit, part of the archive had been damaged by fire. We could have lost decades of irreplaceable data. Access to more such documents will help us to improve our reconstructions of climate history or refine our predictions of future climate change in this part of the world, where adaptation to the impacts of climate change is already a necessity.”
Wim Thiery, lead author of the study and professor at the VUB, said:
“Our research provides new observational evidence of climate change in this region, where, although little data is available, it is of great climatological importance. This is particularly important because Central Africa remains one of the few regions where the latest report from the Intergovernmental Panel on Climate Change (IPCC) was unable to confirm an increase in extreme heat, largely due to the lack of historical observations and scientific research. Our research also highlights the urgent need for more data-rescue projects, particularly in data-poor regions, to fill knowledge gaps regarding climate trends. This is especially important for regions in the Global South that are already being severely affected by climate change. These regions are the least responsible for climate change, yet are the hardest hit by its consequences, and these new observations will contribute to decision-making on adaptation and a just transition.”
Via this link, you will find a complete press pack containing: the press release in various languages, the research article and previous studies, as well as photographs and maps illustrating this research. |
Contact
- Lead author: Derrick Muheki, Department of Water and Climate, Vrije Universiteit Brussel; derrick.muheki@vub.be, +32 470 34 64 23.
- Senior Author: Prof. Dr Wim Thiery, Department of Water and Climate, Vrije Universiteit Brussel; wim.thiery@vub.be, +32 2 629 30 29.
- Policy Impact Lead: Dr Marie Cavitte, Department of Water and Climate, Vrije Universiteit Brussel; marie.cavitte@vub.be, +32 470 19 24 15.
Koen Stein
