Summary:
Decades of handwritten weather observations from the Democratic Republic of the Congo (DRC) have provided new evidence of rising temperatures and increasingly frequent hot extremes in one of the world’s least-monitored climate regions.
Researchers led by Vrije Universiteit Brussel (VUB) recovered more than one million weather observations from 37 stations, using machine-learning software to convert historical paper records into digital data. The study, published in Earth System Dynamics, examined temperature trends at 21 stations with sufficiently complete records.
Between 1961 and 1990, median warming trends across these stations corresponded to approximately 0.7 °C for daily maximum temperatures and 0.5 °C for average daily temperatures. Hot extremes also became more frequent, with the annual number of unusually hot days based on average daily temperatures doubling between 1961–1970 and 1981–1990. Cold extremes became less common.
Heavy rainfall became more frequent at two of the three stations examined, although limited records prevent broader regional conclusions.
The research provides observational evidence of historical warming in Central Africa and demonstrates how recovering archived weather measurements can improve climate assessments in regions with limited monitoring data.
— Press Release —
Hot days become twice as common between 1960 and 1990 in the Congo Basin: Proofs rescued from paper archives
New research led by Vrije Universiteit Brussel (VUB), and published in the journal Earth System Dynamics, shows a clear warming signal across the Congo Basin since the 1960s, using historical weather records from the Democratic Republic of the Congo (DRC). These records come from the paper archives of the Institut National pour l’Etude et la Recherche Agronomiques (INERA) in Yangambi, DRC, and the State Archives of Belgium.
Over two field campaigns in 2023, Derrick Muheki, researcher at the VUB and lead author of the study, in collaboration with INERA staff and Ghent University (UGent), photographed over 9,000 handwritten monthly sheets of weather observations, recorded at 37 stations across the DRC. Using MeteoSaver, an award-winning open-source software developed by Muheki at the VUB in collaboration with the UGhent Centre for Digital Humanities’ team, the research team automatically transcribed these observations into digital spreadsheets that they used to understand temperature and rainfall evolution across the Congo Basin.
The resulting database contains more than one million daily (and sometimes sub-daily) weather observations which, together with previously rescued data, represent one of the largest climate datasets for the Congo Basin region, which had until now been overlooked by the research community.
Upon analysing this new database, the authors document for the first time the evolution of hot extremes in the Congo Basin since the 1960s:
- Daily maximum, minimum and average temperatures rose by tenths of a degree per decade over 1961-1990. Over 1961–1990, maximum temperatures warmed by about 0.7 °C, minimum temperatures warmed by 0.3 °C, and average temperatures warmed by 0.5 °C.
- This warming of the Congo Basin continues into the 2000s, using data from weather stations with longer records in time.
- Each successive decade shows an increase in the number of hot days per year, with hot days getting hotter, while the number of cold days decreases, consistent with trends around the world. On average, the number of hot days per year nearly doubled between the 60s and the 80s, confirming the unequivocal warming trend in the region.
Examining past rainfall from 3 weather stations, the authors also observe that the number of heavy rainfall events at 2 of these stations doubled in the 80s versus the 60s. This observed increase in how often and how intense weather extreme events happen in the DRC is consistent with trends around the world, linked to increasing global temperatures driven by continued fossil fuel emissions.
Historical climate data over Central Africa have until now been extremely sparse, and this open-access database contributes new observational evidence to set the climate context for a region that is strongly impacted by climate change today. It also provides important information to evaluate and improve climate models in the region and underscores the importance of data rescue efforts around the world.
Derrick Muheki, lead author of the study and PhD researcher at VUB, said:
“Seeing how fragile these paper archives were as I was visiting INERA made me realise how urgent this data rescue work is. Just months before my visit, part of the archive had been damaged by fire. We could have lost decades of irreplaceable data. Accessing more or these records will help us improve reconstructions of our climate history or improve our projections of future climate change in this part of the world, where adaptation to climate impacts is already a necessity.”
Wim Thiery, Senior author of the study and Professor at VUB, said:
“Our research provides new observational evidence of climate change in this data-sparse yet climatically significant region. This is particularly important because Central Africa remains one of the few regions where the last Intergovernmental Panel on Climate Change (IPCC) report could not confirm an increase in hot extremes, largely due to the lack of past observations and scientific studies. Our work further highlights the urgent need for more data rescue projects, especially in data-sparse regions, to close knowledge gaps on climate trends.
“This is particularly important for regions in the Global South that are severely impacted by climate change already today. These regions are least responsible for climate changes, yet suffer the brunt of the impacts, and these new observations will help inform decision-making when it comes to adaptation and a just transition.”
Journal Reference:
Muheki, D., Hufkens, K., Jacobsen, K., Verbeeck, H., Boeckx, P., Kankonde Ntumba, D., Kapalay Moulasa, O., Vercruysse, B., Birkholz, J. M., Verbruggen, C., Hawkins, E., Lampe, S., Yakusu, E. K., Imwangana, F. M., Mbifo, J., Likwela, T. B., Meunier, F., Dewitte, O., Thorne, P., and Thiery, W., ‘From paper to proof: revealing Congo Basin warming through rescued climate archives’, Earth System Dynamics 17, (5) pp. 1455–1511 (2026). DOI: 10.5194/esd-17-1455-2026
Article Source:
Press Release/Material by Koen Stein | Vrije Universiteit Brussel (VUB)
Featured image: Photo taken at the INERA – Section de Climatologie site in Yangambi, Democratic Republic of the Congo, while digitizing the meteorological paper archives in 2023. The shelves shown contain thousands of paper-based meteorological records spanning several decades, and form the foundation of the climate data rescue efforts. Credit: Derrick Muheki
