Why coming rains will be so extreme

Scientists have predicted that the frequency and intensity of heavy extreme rainfall will increase in Eastern Africa in the coming few weeks. 

This is after findings of a new study done by the International Livestock Research Institute (ILRI) showed an increase in intense rainfall, which scientists say could lead to a rise in food hazards in areas where intense rain typically triggers inundations.

These findings confirm the announcement by the Intergovernmental Authority on Development Climate Prediction and Applications Centre (ICPAC) last year during the same period that rainfall surplus is expected to dominate over the Greater Horn of Africa region in the March-May season.

According to the centre, the rainfall surplus will likely dictate the weather conditions, especially over Southern Ethiopia, Kenya, Somalia, Burundi and Tanzania. Considering this seasonal forecast, the centre is now calling for strengthened emergency preparedness and anticipatory actions.

 “As a result, crop and livestock production will likely be at high risk in the region,” the scientists highlighted at the 66th Greater Horn of Africa Climate Outlook Forum of ICPAC for the March to May 2024 season held in Kampala, Uganda; under the theme “Early Warning for Anticipatory Action”. 

In an interview with Climate Action, Dr Teferi Demissie, the lead author of the new study titled ‘Current and projected changes in climate extremes and agro-climatic zones over East Africa’, said they used an ensemble of seven global climate models. 

 According to the expert, the water extreme/stress indicators considered include indices to indicate drought and flood situations.

“The heat stress indicators are composed of the frequency of hot spells and the duration and intensity of heatwaves. As expected, all heat stress indicators are projected to increase in future climates,” he observed, adding that the frequency and intensity of heavy precipitation events are also projected to increase with increased greenhouse gas emissions.

“The drought stress indicators follow the precipitation pattern.”

“A heterogeneous response of the agro-climate regime to climate change is projected for Eastern Africa, with some areas (such as southern Tanzania) experiencing alterations towards drier zones while others (such as northern Somalia and South Sudan) are experiencing a shift towards wetter zones,” the lead author and ILRI researcher explained to Climate Action.

 The scientists are of the view that the increase in short-duration heavy precipitation events together with the enhanced pace of heat stress over the region will have critical implications for agriculture in general and local livestock production in particular.

But why is this happening in Eastern Africa?

Dr Dimissie explains that East Africa has diverse climatic conditions ranging from hot and dry conditions over the northern rift valley of the Afar region, to cold and wet areas of the Ethiopian highlands and parts of Uganda and Congo.

Therefore, such diverseness arises due to the complex topography of the region as well the unique interaction of local microclimate, regional circulation, large-scale modes of variability, and the global climate system. 

“The large-scale drivers of these climatic conditions include Inter-tropical Convergence Zone, equatorial Pacific Sea surface temperature, Indian Ocean Dipole and other global modes of variabilities,” he notes. 

Regarding the rainfall regime, the equatorial regions have two rainy seasons — the main or long rainy season from March to May and a short or secondary season from October to December.

“The northern part of East Africa, namely northern Ethiopia, Eritrea, and Sudan, has a single rainfall season from June to September,” says the study, adding that the Intergovernmental Panel on Climate Change assessment reports and other studies have demonstrated the consequence of increased greenhouse gas concentrations on climate, albeit on a global and regional level.

Another elephant in the room is that having diverse climatic conditions, as in East Africa, has resulted in different land use patterns and, hence, agricultural practices such as crop cultivation in the wet regions and livestock production in the semi-arid and arid regions.

Yet in most semi-arid regions, livestock production enables farmers to diversify incomes and is crucial for coping mechanisms in poor households. 

This is why climate variability and change pose significant challenges for the agriculture sector in general and livestock production systems in particular.

Scientists believe that this assessment will help gain a better understanding of suitable environmental factors related to livestock production and how anthropogenic climate change may lead to shifts in the location of these environmental factors. 

Their hope is that this, in turn, should lead to improved dissemination of intervention options.

“One of the specific objectives of this study is to determine the variation in agro-climatological zones over East Africa associated with anthropogenic climate change.This includes classifying the East African region into homogeneous agro-climatic zones for the historical climate period as well as comparing the future changes with respect to the current situation using the latest climate models,” says Dr Dimissie.

 While addressing delegates in Kampala, Dr Hussen Endris, a climate modelling expert and researcher at ICPAC, indicated that temperatures are expected to be warmer than average all over the region, with enhanced probabilities shown over the northern parts of the region.

 “Delayed onset is indicated over localised areas in Central Kenya as well as parts of southern and north-western Ethiopia,” the expert noted, adding that wetter than usual conditions are expected in most parts of the Greater Horn of Africa.

In comparison, drier conditions are predicted over parts of eastern Tanzania and localised areas in western South Sudan.

“For some seasons in East Africa (such as the Northern Monsoon in June to September, and the Short Rains in October to December), the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) play a large role in seasonal rainfall variability from year to year,” Dr Stefan Lines from the Meteorological Office ,United Kingdom, said while pointing a finger at atmospheric processes such as the Madden-Julian Oscillations — weather dynamics happening on water bodies that can bring significantly enhanced rainfall on shorter (monthly) timescales.

He added that long rains are traditionally very difficult to forecast accurately on seasonal timescales. ICPAC’s forecasting methodology looks beyond just ENSO and the IOD and uses the most powerful seasonal forecasting models to predict the season ahead.

“Record-breaking global temperatures were observed in 2023, and temperatures are likely to be similar or even exceed,” the expert highlighted, adding that this warmth is due to human-induced climate change and the intense El Nino event, which peaked in December.

“El Nino events release a significant amount of heat into the atmosphere.”

According to the United Nations, between September and December 2023, El Niño-induced rains and flooding (riverine and flash floods) heavily affected parts of the Eastern African region, including Burundi, Ethiopia, Kenya, Rwanda, Somalia, South Sudan, Sudan, Tanzania, and Uganda, leading to loss of lives, livelihoods, and displacement. More than 5.2 million people were affected. 

[email protected]