- Researchers said El Niño and the Indian Ocean Dipole did not influenced this year’s deluge: it was climate change.
- They urged readiness for next rains, saying impacts worse due to rapid urbanisation, informal settlements near water.
Image: Stanley Njenga
A new report warns the extreme rainfall that led to devastating floods in Kenya and other parts of East Africa will become more intense.
The study by an international team of leading climate scientists from the World Weather Attribution Group says climate change is one of the drivers of such flooding.
The study highlights that East African cities face double pressure from rapid urbanisation and changing climate risks. Climate models project that heavy rainfall will continue to increase in the region with further warming.
London researcher Joyce Kimutai, said historically, long rains in East Africa have been challenging to study, as weather observations show a drying trend in the region and climate models project more rains with climate change.
She works at the Grantham Institute on Climate Change and the Environment, Imperial College, London.
“But in recent years, this appears to be changing, and new climate models seem to better reflect how long rains are behaving with global warming," she said.
Kimutai said the most recent weather observations and the latest climate models are more in agreement and show that the long rains are bringing more and more rain every year and that with further warming, they will become even more intense and dangerous.
"We need to be prepared for this new reality and to stop burning fossil fuels to avoid worsening an already a dire situation,” she said.
Julie Arrighi, Associate Director at the Red Cross Red Crescent Climate Centre, said the study highlights the dual pressure from rapid urbanisation and changing climate risks across cities in East Africa.
“East Africa is one of the world’s fastest urbanising regions, a pressure that would be challenging on its own. Coupled with more frequent and intense extreme weather, such as heavy rains , more people will be in harm's way. There is an urgent need to further scale-up inclusive urban planning measures and adaptation investments to reduce risks.”
Between March and April 2024, extreme rain caused devastating floods in several countries of East Africa.
The rainfall led to rivers overflowing and landslides in highland regions, affecting more than 750,000 people and displacing hundreds of thousands.
At least 291 people died in Kenya and 155 in Tanzania.
Much of the impact was in large and highly populated cities, particularly the informal settlements of Nairobi.
Across the region, the downpours also killed 4,000 livestock and destroyed 27,000 acres of crops.
These new floods take place against the backdrop of a three-year-long drought. The region was still recovering from another extreme rainfall episode in October-November 2023.
Both events were made more severe due to climate change, as shown by two previous WWA studies.
To understand the effect of human-caused warming on the 2024 floods, scientists analysed weather data and climate models to compare how these types of events have changed between today’s climate, with approximately 1.2 degrees Celsius of global warming, and the cooler pre-industrial climate, using peer-reviewed methods.
The study looked at the maximum 30-day rainfall during the long rains, from March to May, and focused on a region that includes southern Kenya, most of Tanzania, and the areas around Lake Tanganyika, in Burundi, where the impacts were most severe.
Weather observations across the region show the amount of rainfall during the long rains decreased from the mid-1990s until 2008.
However, in the last 15 years, the March-May period has become wetter again, with an increasing trend in rainfall.
Climate models also show a small trend towards more frequent and intense rainfall due to climate change.
While this result has a large amount of mathematical uncertainty and is not statistically significant, the best estimate is that climate change made the event twice as likely and five per cent more intense.
The analysis also showed that, with further warming, climate change is expected to continue to increase rainfall.
At 2 degrees Celsius warming, the majority of the climate models show an additional increase in frequency and intensity, with a smaller uncertainty than for the current climate.
The researchers did not find any evidence that El Niño or the Indian Ocean Dipole had any influence on this year’s deluge.
With heavy rainfall episodes likely to continue, the researchers said that countries in East Africa must continue building resilience against floods.
Improving existing infrastructure, restoring ecosystems, and putting forward social policies to help people cope with floods are some of the helpful strategies.
This is particularly important in cities, where a large share of the population lives in informal settlements.
This rapid urbanisation, with houses built in flood-prone regions such as river banks and wetlands, contributed to worsening the impacts. In the context of increasing rainfall events due to climate change, urban planning that accounts for growing informal populations is key to avoiding further increasing the risk to human lives.
The study was conducted by 13 researchers as part of the World Weather Attribution Group, including scientists from universities, research organisations, and meteorological agencies in Kenya, Sweden, the Netherlands, Germany, the United Kingdom, and the United States.