Scientists from Italy, the Netherlands, Sweden, the UK, the European Commission and the US used published peer-reviewed methods to assess whether and to what extent climate change influenced the 12.month drought in the two islands (1) Sicily and (2) Sardinia.

There are several ways to characterise a drought: meteorological drought is defined only by low rainfall, while agricultural drought combines rainfall estimates with evapotranspiration or directly measures soil-moisture content. As increased evapotranspiration due to regional warming can play a major role in exacerbating drought impacts, we assess agricultural drought in this study by means of  the Standardised Precipitation Evapotranspiration Index (SPEI), which calculates the difference between rainfall and potential evapotranspiration to estimate the available water. The more negative the SPEI values are, the more severe the drought is classified. Figure 1 shows the SPEI for the 12 months between July 2023 and August 2024 over Italy, and the category it falls in according to the US Global Drought Monitor classification system.  

Main findings

• The main economic activities in Sicily, agriculture and tourism, both strongly depend on water availability. The economic consequences of this drought are thus catastrophic for many in the region and recovery will take time. In Sardinia, agriculture is economically less important, but of high cultural relevance; leading to challenges with water prioritisation for domestic and agricultural use on both islands. 
• Natural ecosystems also suffer. Agricultural expansion, especially in Sicily, has increased water demand, with a decrease of 62ha per year since 1990 in natural ecosystems, including wetlands. 
• In different observational datasets the extreme drought, defined by SPEI12 (fig. 1) is among the most severe droughts since records began. All data agree that this drought is not very rare in Sardinia in today’s climate that has warmed by 1.3°C primarily due to the burning of fossil fuels, with a return period of about 10 years (3 – 93 years). In Sicily, such a drought does not occur very often, with a best estimated return period of around 100 years (10- 200,000 years) in today’s climate. 
• Based on the US Drought Monitoring Classification system, the 1-in-10 year drought over Sardinia which is an ‘extreme’ (D3) drought now would be classified as a ‘severe’ (D2) drought without the effects of climate change, and with further warming would be a more severe ‘extreme’ drought (D3). The rare 1-in-100 year drought over Sicily which is also an ‘extreme’ (D3) drought would be a ‘severe’ (D2) drought without climate change, and with a further 0.7C of warming, will become an ‘exceptional’ drought (D4). For both islands, the likelihood of a drought as defined by SPEI12 from August 2023 to July 2024 has increased by about 50% due to human-induced climate change. 
• To understand the meteorological drivers of these changes in drought, we also assess the individual components making up the drought index, namely rainfall, potential evapotranspiration and temperature. We find that changes in rainfall are small and not statistically significant: on the contrary, both values observed for potential evapotranspiration and temperature as observed this year would have been almost impossible to occur without human-induced climate change. We thus conclude that this increase in drought severity is primarily driven by the very strong increase in extreme temperatures due to human-induced climate change. 
• It has been well-established that climate models tend to underestimate the increase in extreme temperatures in Europe; this in part accounts for the discrepancy between the observed change in drought frequency and intensity and those represented in climate models. 
• Unless the world rapidly stops burning fossil fuels, these events will become even more common in the future. In a world 2°C warmer than preindustrial, which could happen as soon as 2050 without large and rapid reductions in greenhouse gas emissions, droughts like the ones in Sicily and Sardinia will become more frequent. 
• Effective drought risk management in regions such as Sardinia and Sicily requires a sustained focus on long-term preparedness and adaptation. Investing in resilient infrastructure, water conservation strategies, and sustainable resource management is crucial to mitigating the impacts of drought.

Rainfall in Panama is known to be strongly influenced by the El Niño Southern Oscillation (ENSO), with large storms and extremely heavy precipitation tending to occur in the negative phase (La Niña years) and the positive phase (El Niño years such as 2023-24) typically associated with late onset and early end of the rainy season, and lower precipitation throughout. 

Scientists from Panama, the Netherlands, Sweden, and the United Kingdom collaborated to assess to what extent the 2023-4 El Niño and human-induced climate change altered the likelihood and intensity of the low rainfall during 2023, and also examined whether changes in evapotranspiration may have contributed to the low lake levels.  

The study uses peer-reviewed methods to assess changes in May-December rainfall in the area immediately around the catchment of Lake Gatun in central Panama (Figure 1b). Potential evapotranspiration is evaluated over the same region during the dry season (January-April).

Main findings

• The rainfall deficits not only affect global shipping, but also the people who live and work in the Panama Canal Watershed. Indigenous, Afro-Panamanian, and some rural communities have water-dependent livelihoods and limited access to basic services such as electricity, water and sanitation. Therefore, even small changes in rainfall can have disproportionate impacts on their livelihoods, highlighting the interplay between climate and economic deprivation. 
• Urban expansion and population growth, combined with aging infrastructure that loses significant amounts of water through leaks, are increasing pressure on water supplies, especially during dry periods. 
• Restrictions on shipping through the Panama Canal have wide-ranging global impacts. Many ships now have to take longer shipping routes, which worsens delays at other ports and drives demand for trucking and rail services, increasing costs and greenhouse gas emissions.
• Reduced revenue for the Panama Canal Authority could threaten employment in canal-related industries, and can worsen existing socio-economic challenges for local communities and in developing countries vulnerable to inflation increases. 
• Low rainfall during the 2023 rainy season (May-December) has contributed to extremely low water levels in Lake Gatun in Panama despite above-average water levels in the lake at the beginning of the year.
• Historically, the lowest lake levels have occurred the year after low-precipitation rainy seasons: lake levels remained at a seasonal low during the first three months of 2024 but are expected to begin to recover with the onset of the rainy season in May.
• During El Niño conditions in the current climate, with 1.2C of warming, an event of this magnitude is expected to happen more often than under neutral ENSO conditions. In the present climate, there is a 5% chance of such an event occurring in an El Niño year. Given the observed frequency of El Niño years, this means that similar events would be expected to occur around once every 40 years in the current climate that has been warmed by 1.2C due to the burning of fossil fuels. We expect around 8% less precipitation in an El Niño year than under neutral ENSO conditions.
• There is some evidence of drying in the observational record, especially in stations bordering the lake, but other stations in the study area show a wettening. The  gridded observational data-products, which are much shorter than the station data, do not consistently exhibit a drying trend.
• To identify whether this trend is due to human-induced climate change we then also look at climate models with high enough resolution to capture precipitation over the study region. Only one of the available climate models show a similar drying, while all others either show no trend or a wettening. 
• With neither climate model data nor a strong physical argument to support the hypothesis, we therefore cannot conclude that the observed drying is attributable to human-caused climate change.
• Evapotranspiration in Panama is mainly driven by wind speed, humidity and cloud cover which is in contrast to most other regions in the world, where temperature is a key driver. Although there is evidence in some of the observational products that evapotranspiration in the region will increase in a warming climate, the amount of water lost annually through evapotranspiration in this area is small compared to the rainfall deficits from  lack of rainfall.
• Future trends in this region under continued warming are also uncertain. However, future El Niño years will continue to bring low rainfall and, without adaptation action, similarly low lake levels.

Years with a positive phase of the El Niño Southern Oscillation (ENSO) have been associated with droughts in that region in the past, but impacts have not been homogenous, with some El Niño events leading to droughts while others did not. This is because other climate modes of variability such as
Indian Ocean Dipole and Subtropical Indian Ocean Dipole play a critical role in the rainfall amount and distribution over the affected region.

Furthermore, human-induced climate change has been found to increase aridity in some regions in Southeastern Africa, but studies encompassing the countries affected by the 2024 drought, which has been reported to be the worst on record in parts of Zambia and Zimbabwe, are sparse and often focus on much larger regional averages.

Scientists from Zambia, Botswana, Kenya, Mozambique, South Africa, the Netherlands, Sweden, and the United Kingdom collaborated to assess to what extent the 2024 ENSO state as well as human-induced climate change altered the likelihood and intensity of the low rainfall that led to drought, as well as the increase in evaporation due to climate change, exacerbating drought severity.

We focus the analysis on the most affected countries, Zimbabwe, Botswana, Zambia and Mozambique but only the Southern parts for the last two countries to study a climatologically homogeneous region. The temporal focus is December to February (DJF), the peak of the rainy season in the region.

Main findings

● Reliance on rain-fed subsistence crop production and drought-sensitive water sources result in chronic high vulnerability to rainfall anomalies, and limited coping capacity.
● Multiple drivers contributed to the currently high, and rising, food insecurity and malnutrition levels including several years with high food prices, ongoing recovery from floods, as well as agricultural pests and diseases.
● High deforestation rates are a major driver of environmental degradation across the countries, exacerbating risk and impacts associated with drought.
● Using four different observational data products we find that droughts such as this one are expected to happen in today’s climate about once every decade. However, when we consider the effect of El Niño, we find that these droughts are twice as likely to occur in El Niño years. Thus El Nino is a key driver of the 2024 event.
● To analyse the role of human-induced climate change we first looked at the relationship between global warming and rainfall anomalies in observation-based data products. We find that as global temperatures increase, rainfall in DJF also increases. This means that in the current climate, with 1.2ºC warming, droughts such as this one are actually less likely than in a cooler, pre-industrial climate. This finding is consistent with previous studies that show wetter conditions in DJF that contrast with drying in the region earlier in the season, between the months of September and November).
● To further evaluate the role of climate change in the current drought we combined the observations with climate models. The models that passed the model evaluation do not show a significant relationship between rainfall and global warming levels with increasing global temperatures.
● The analysis also indicates that with further global warming of up to 2ºC there will be no significant change in the likelihood of low rainfall in DJF as observed in the region in early 2024.
● Repeating all the analysis for the effective precipitation, taking evapotranspiration into account and only looking at water that is actually available for plants, we find very similar results.
● In summary, our analyses show that El Nino significantly increases the likelihood of such a drought to occur, while climate change did not emerge as the significant driver influencing assessed drought in the affected countries.
● As El Nino events will continue to occur in a warming climate it is important to increase resilience to droughts that will continue to occur frequently.
● Countries in the region have varying levels of development, infrastructure, and governance systems that impact their ability to respond to the drought. For example Botswana is relatively more developed than the other countries in the study and its economy and people are less reliant on rain-fed agriculture, resulting in fewer impacts.
● Maintaining robust traditional land governance systems with appropriate integration into modern frameworks appears crucial for sustainable land management and reducing drought vulnerability to southern Africa.
● Effective early warning systems, anticipatory action, and coordinated emergency response efforts are in place, and could be further strengthened by commitments for shock responsive social protection systems.

The large riverine system powers significant portions of the affected countries’ energy through hydropower, with Brazil relying on hydro power for 80% of its electricity, Colombia 79%, Venezuela 68%, Ecuador and Peru 55%, and Bolivia 32% (USaids, 2018). The drought is significantly impacting dam capacities and energy output and led to power cuts in the region as early as June 2023. 

Scientists from Brazil, the Netherlands, the UK and the US used published peer-reviewed methods to assess whether and to what extent the drought has been influenced by climate change as well as the occurrence of El Niño, which is known to be associated with drought in the Amazon. While the drought started earlier in the west of the basin, the whole basin has been in severe or exceptional drought for the second half of the year (Fig. 1 blue outline). 

There are several ways to characterise a drought. Meteorological drought considers only low rainfall, while agricultural drought combines rainfall estimates with evapotranspiration. Increased evapotranspiration due to regional warming can play a major role in exacerbating drought impacts. In this study we assess agricultural drought as well as meteorological drought. The main variable used here to characterise agricultural drought is the Standardised Precipitation Evapotranspiration Index (SPEI) (figure 1) which uses the difference between rainfall and potential evapotranspiration to estimate the available water. The more negative the values are, the more severe the drought is classified. Meteorological drought is analysed here using an index (SPI) based on precipitation alone. 

Main findings

• Highly vulnerable populations were disproportionately affected by the drought. Small-holder farmers, indigenous-, rural- and river communities across the region were among the most vulnerable due to high poverty rates and their high dependency on agricultural food production, availability of freshwater, and import of goods via rivers. 
• Exposure to drought impacts was compounded by historical land, water, and energy management practices including deforestation, destruction of vegetation, fires, biomass burning, corporate farming, cattle ranching and other socio-climate problems which have decreased the water and moisture retention capacity of the land and thus worsened drought conditions.
• In datasets based on weather records the drought is exceptional, even in today’s climate, characterised as a 1 in 100 year event for the meteorological drought (SPI) and approx. a 1 in 50 year event in SPEI. While there is a strong drying trend in the meteorological drought, the trend in agricultural drought is even stronger meaning this agricultural drought would have been extremely rare in a cooler climate. 
• We first assess to what extent El Niño is a driver of this trend. El Niño reduced the amount of precipitation in the region by about the same amount as climate change; however, the strong drying trend was almost entirely due to increased global temperatures, so the severity of the drought currently being experienced is largely driven by climate change.
• In order to assess whether and to what extent human-induced climate change was a driver of this drought we combine observations-based data products and climate models and look at the 6 month meteorological (SPI6) drought as well as agricultural drought (SPEI6). We find that the likelihood of the meteorological drought occurring has increased by a factor of 10, while the agricultural drought has become about 30 times more likely. 
• Using the US drought monitoring classification system, based on agricultural drought, this means that what is now classified an exceptional drought (D4), would have only been a ‘severe drought’ (D2) without the effects of climate change, caused by burning fossil fuels and deforestation. 
• Unless the world rapidly stops burning fossil fuels and deforestation, these events will become even more common in the future. In a world 2°C warmer than preindustrial an event like this would become even more likely by a further factor of 4 for the agricultural drought (every 10-15 years) and a further factor of 3 for the meteorological drought (every ~30 years). 
• While all countries in the affected region have drought management plans, the recent droughts indicate a need to reform policy and better integrate proactive support for forecasts and early warnings, drought contingency plans,  sustainable water management practices and infrastructure investment to cope with future, more intense droughts. 
• These results highlight that despite ‘low confidence’ in IPCC projections for drought in the region, increasing water stress driven by human-induced climate change as well as other systemic factors continues to be a major threat for the population and requires urgent efforts for more effective water management strategies, interdisciplinary humanitarian response, and regional cooperation that includes farmers and other stakeholders in the planning.

Scientists from Iran, the Netherlands, the UK and the US used published peer-reviewed methods to assess whether and to what extent climate change influenced the 3-year drought in two regions: (1) the fertile crescent around the Euphrates and Tigris rivers, encompassing large parts of Iraq and Syria and (2) Iran. There are several ways to characterise a drought: meteorological drought considers only low rainfall, while agricultural drought combines rainfall estimates with evaporation. As increased evapotranspiration due to regional warming can play a major role in exacerbating drought impacts, we assess agricultural drought in this study. The main variable used to characterise the drought is the Standardised Precipitation Evapotranspiration Index (SPEI) which calculates the difference between rainfall and potential evapotranspiration to estimate the available water. The more negative the values are, the more severe the drought is classified. Figure 1 depicts the SPEI classification for the 36 months from July 2020 up to June 2023 over the two study regions. 

Main findings

• The drought affects a region with a highly vulnerable population due to varying degrees of fragility and conflict including war and post-war transition, rapid urbanisation in the face of limited technical capacity, and regional instability. These dynamics increased vulnerability to the impacts of drought and created a humanitarian crisis.
• The whole Euphrates and Tigris basin (ET-basin) and large parts of Iran experienced extreme and exceptional agricultural drought over the 36 months up to June 2023, making it the second-worst drought on record in both regions based on SPEI. 
• The extreme nature of the drought is not rare in the present climate (which has been warmed by 1.2°C due to burning of fossil fuels). Events of comparable severity are expected to occur at least every decade. 
• Using three different observations-based data products we find a strong trend towards more severe droughts in both regions. We find that the combination of low rainfall and high evapotranspiration as unusual as the recent conditions – that is, an event that occurred around every 5-10 years – in a world that had not been warmed 1.2°C  would be so much less severe that nowadays it would not be classified as a drought at all.
• In order to identify whether and to what extent human-induced climate change was a driver of these trends we combine observations-based data products and climate models and look at the 36-month SPEI in both regions. We find that over the ET-basin the likelihood of such a drought occurring has increased by a factor of 25 compared to a 1.2°C cooler world. Over Iran the likelihood of such a drought occurring has increased by a factor of 16 compared to a 1.2°C cooler world. 
• For both regions human-induced climate change has increased the intensity of such a drought such that it would not have been classified as a drought in a 1.2°C cooler world. Thus confirming that the observed finding is indeed caused by human-induced climate change. 
• To understand the meteorological drivers behind this change in agricultural drought we also analysed rainfall and temperature separately and found there to be little change in the likelihood and intensity of rainfall but a very large increase in temperature. We thus conclude that this strong increase in drought severity is primarily driven by the very strong increase in extreme temperatures due to the burning of fossil fuels. 
• Unless the world rapidly stops burning fossil fuels, these events will become even more common in the future. In a world 2°C warmer than preindustrial an event like this would be an exceptional drought, the worst category possible. 
• The high levels of water stress in the region today are exacerbated by limitations in technical capacity, water management, and regional cooperation. Rapid population growth, industrialization and land-use changes, dam practices and river flow management between upstream and downstream countries, aged water treatment plants, and low efficiency of irrigation water systems have contributed to a complex water crisis. Water is moreover weaponised in conflict, with water systems increasingly targeted for sabotage.
• These results highlight that despite ‘low confidence’ in IPCC projections for drought in the region, increasing water stress driven by human-induced climate change as well as other systemic factors continues to be a major threat for the population and requires urgent efforts for more effective water management strategies, interdisciplinary humanitarian response, and regional cooperation that includes farmers and other stakeholders in the planning. 

The drought has led to substantial harvest failure, poor pasture conditions, livestock losses, decreased surface water availability and human conflicts, leaving 4.35 million people in need of humanitarian assistance (NDMA, 2022). At least 180,000 refugees from Somalia and South Sudan crossed into the drought-stricken areas of Kenya and Ethiopia (UNHCR).

By January 2023, close to 9,210 MT of food commodities had been distributed and USD 7.29 million cash-based transfers had been made (OCHA, 2023). Despite some reported rains in parts of Kenya by the end of March 2023 (KMD, 2023), the drought conditions are not likely to recover quickly enough to see improvements in food security before mid-2023. 

Scientists from Kenya, Mozambique, South Africa, the United States of America, the Netherlands, Germany and the United Kingdom collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the low rainfall that led to drought, as well as the increase in evaporation due to climate change, exacerbating drought severity. 

Figure 1: Left: Drought classifications based on Standardised Precipitation Index (SPI; US Drought Monitor, 2023), reflecting the magnitudes of  precipitation deficit from Jan 2021-Dec 2022 relative to the 1980-2010 climatology in the CPC dataset. Right: Drought classifications based on Standardised Precipitation Evapotranspiration Index (SPEI), reflecting the magnitudes of precipitation deficit from Jan 2021-Dec 2022 relative to the 1980-2010 climatology in the CPC dataset. The bold black outline highlights the study region.

Figure 2: Joint distribution of 24-month precip and PET with corresponding SPEI drought classification. The solid contours indicate return periods under the joint distribution in the current climate, while the dashed contours indicate the same return periods in a 1.2°C cooler climate. The shaded contours represent different levels of drought severity. The magenta point indicates the 2022 drought event in the current climate, with a joint return period of 26 years (uncertainty: 23-37 years), while the turquoise point shows an event of the equivalent severity in a 1.2°C cooler climate.

Main findings

• The Southern part of the Horn of Africa, covering parts of southern Ethiopia, southern Somalia, and eastern Kenya (see figure 1), saw below average rainfall for the short rains (October-December) in 2020, 2021 and 2022 as well as the long rains (March-May) in 2021 and 2022. 
• As one of the world’s most impoverished regions, the Horn of Africa is home to millions of people facing chronic food and water insecurity, malnutrition, and limited access to basic services including infrastructure, health care, education, and social welfare. The ongoing drought has turned these underlying conditions into acute food insecurity for over 4 million inhabitants. 
• In order to identify whether human-induced climate change was a driver of the low rainfall, i.e the meteorological drought, we analysed rainfall over the most impacted region in the Southern Horn of Africa, covering parts of southern Ethiopia, southern Somalia, and eastern Kenya, for 24 consecutive months, from January 2021 to December 2022, as well as just the individual 2022 March-May and October-December seasons separately.
• We find that in today’s climate, which has been warmed about 1.2°C by human-induced greenhouse gas emissions,  the below-average rainfall in the March-May season is a 1 in 10 year event, a 1 in 5 year event in the short rains. For the entire 24-month period there is a 5% chance in every year for such an event to develop.
• Using two observation-based rainfall products we find there is a trend towards less rainfall in the long rains but not over the short rains, which show the opposite, a wettening. There is no trend when looking at the short and long rains combined over 24 months.
• The years of the drought also saw consecutive La Niña conditions. There is a high correlation between below-average short rains and La Niña, but there is no correlation with the long rains. When taking into account the effect of La Niña there is a trend towards wetter conditions in the short rains. 
• To formally attribute these trends to climate change and to try to quantify its contribution to the drought, we used climate models and looked at similarly low rainfall events over the same region in the model data. We found that the models show similar results to the observations: low rainfall events like those currently observed in the long rains have become about twice as likely due to human-induced climate change, while there is no attributable change when short and long rains are combined. In the short rains, models where the effect of La Niña is taken into account show that a low rainfall season like the one observed has become less likely, making the increased rainfall in the short rains attributable to human-induced climate change. 
• In order to understand whether climate change influenced not only the meteorological drought (i.e. low rainfall), but also other aspects of the drought, including the agricultural drought which influences how much water is available for plants, we also looked at the role of temperature. To do this we combined the rainfall assessment with an assessment of changes in potential evapotranspiration, i.e. how much water evaporates from soil and plants because of higher temperatures, in a multivariate analysis for the 24 months of drought.
• We found that, as a result of human-induced climate change, the combination of low rainfall and high evapotranspiration as unusual as the recent conditions would not have led to drought at all in a 1.2°C cooler world (see figure 2). In today’s climate the same event is now classified as an exceptional drought (D4, dark red in fig. 1), with major crop and pasture losses and widespread water shortages. This change in drought severity is primarily due to the strong increase in evaporative demand caused by higher temperatures. 
• Climate change has made events like the current drought much stronger and more likely; a conservative estimate is that such droughts have become about 100 times more likely.
• Fundamental to food security, health, and income, households engaged in rain-fed agriculture, agropastoralism, and pastoralism are vulnerable to drought and are among the most severely impacted groups when crop and livestock health decline. When rains fail these households are are forced to spend their limited assets on buffering losses and damages, and are consequently pushed further into poverty. State fragility and conflict, as well as the length of the drought played a significant role in worsening outcomes, especially for people in Somalia. Further, the severity of impacts linked to the long duration of the drought also raises serious questions about the length of droughts that government drought management systems and the international aid infrastructure should be prepared to handle in the future. 
• The results of the study, coupled with climate projections indicating high confidence of increased heavy precipitation and pluvial floods in the north eastern Africa region (IPCC AR6), is illustrative of the myriad of climate impacts that people and governments in this region are confronted with. Taken together, regional climate variability and the projections indicate the need to invest in adaptation strategies that are robust to both wet and dry extremes, and which can be iterated upon as climate signals emerge and future projections become more certain. 

Scientists from Argentina, Colombia, France, the United States of America, the Netherlands and the United Kingdom collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the low rainfall that led to drought, focussing on the particularly severe three months from October to December 2022.

Using published peer-reviewed methods, the team defined the event by the average precipitation during these three months for the region of largest impacts, outlined in blue in Figure 1, and analysed whether climate change altered the likelihood and intensity of the anomalously low rainfall. Given that the season was also characterised by multiple heatwaves (Rivera et al., 2022), the researchers additionally evaluated the effect of temperature, in particular, whether and to what extent climate change has influenced evapotranspiration, thereby exacerbating the drought.

Main findings

• The ongoing drought has led to severe impacts on agriculture, halving the annual harvests in wheat and soy in Argentina, which in turn is expected to lead to export deficits of 25-50%. The drought impacts hit the population on top of already high inflation and weakening local currency. In Uruguay, more than 75,000 people are suffering from lack of access to potable water; access to water for crops and livestock is also limited.
• Central South America has suffered from drought for the last three years, which saw consecutive La Niña There is a high correlation between the rainfall deficit in the study region during the months of October to December and the Niño 3.4 index. Thus, the rainfall deficit is in part driven by La Niña.
• In order to identify whether human-induced climate change was also a driver of the rainfall deficit, we analysed rainfall over the most impacted region and in 9 representative For the region as a whole, the event has a return period of 20 years, meaning it has a 5% chance of occurrence in any given year. At individual stations, it is a less common event, with return times up to 50 years.
• In the observations over the whole region we observed a trend of reduced rainfall over the last 40 years, although we cannot be confident that this trend is beyond what is expected from natural variability in the region.
• In order to identify whether the reduced rainfall is a real trend beyond natural variability that can be attributed to climate change, we looked at once in 20-year low rainfall events over the same region in climate models and found that the models show that low rainfall events decrease – ie they become wetter; the opposite of the trend observed in most weather records – although this trend is again not significant and is compatible with natural variability. Thus, we cannot attribute the low rainfall to climate change.
• This does not rule out that climate change affected other aspects of the drought. To investigate whether the high temperatures, which are in part attributable to climate change, led to a deficit in water availability, calculated as potential evapotranspiration subtracted from the rainfall, we repeated the analysis for this indicator.
• The results show that, in climate models, the increase in temperature does partly compensate for the increase in rainfall but only to offset the wettening, and does not lead to a significant climate change signal in effective precipitation..
• However, higher temperatures in the region, which have been attributed to climate change, decreased water availability in the models in late 2022, indicating that climate change probably reduced water availability over this period in the observations too, thus increasing agricultural drought, although the study cannot quantify this effect.
• This means even though the reduced rainfall is within the natural variability, consequences of drought are becoming more severe due to the strong increase in extreme heat.
• The high impact of the drought on agriculture and economic activity speaks to the need to reduce vulnerability to drought in this Measures such as improved water efficiency and management, anticipation of drought using seasonal forecasts, and insurance instruments to help farmers weather dry years could improve resilience to these types of events.

In this semi-arid region, the economy largely relies on rain-fed agriculture and pastoralism, and recurrently suffers from drought consequences which are compounded by other socio-economic factors including the war in Ukraine, follow-up impacts of the COVID pandemic on energy and crop prices, conflicts inducing population displacements and political unrest.

Scientists from Burkina Faso, France, Germany, the Netherlands, Sweden, the U.K., and the U.S. used published, peer-reviewed methods to estimate whether climate change was also a driver of the short rainy season and the delayed rainfall onset in the preceding year, 2021, leading to the current food crisis. Three characteristics over the Central Sahel region [3°W,24°E ; 14°N,16°N], shown in Figure 1, are chosen to represent impact-relevant aspects of the drought: (1) the precipitation amount in June, (2) the onset of the rainy season and (3) the duration of the rainy season.

Main findings

• A large part of the population of Central Sahel strongly depends on the annual rains and is thus chronically vulnerable to deviations from a normal season (e.g., delay in the onset of the rainy season, dry period within the rainy season, early end, etc);
• Rainfall during the wet season (June to September) in Central Sahel is highly variable from year to year, rendering sowing dates and crop development subject to large variations and significant unreliability;
• In 2021 the wet season started late in the Sahelian regions of Niger and Chad and was followed by a short – albeit intense – wet period, and a dry September. These dry months within the rainy season occurred during critical development stages for the rain-fed crops. In Niger and Burkina Faso production dropped by 36% and 10% compared with the previous five-year average, leading, in combination with other factors including the Ukraine war, to food insecurity in several countries (from Mali to Chad);
• Using three observational data sets and three indices of the characteristics of the wet season (total rainfall in June, onset, and duration), we found anomalies in the observations of all three indices, but these anomalies were not rare: the late onset and shortness of season both have a return period of about 3 years, and the low precipitation amount about 10 years. These results have relatively large uncertainties (typically a [1.5 – 13] year range) due to the high variability, the short span of datasets (~40 years) and differences across datasets used;
• From these three indices, we could not detect significant trends or a climate change influence in the 2021 rainy season. However, the large uncertainties in the observational data and subsequent difficulties in assessing climate models mean it is not possible to assess whether there is no climate change signal or whether we cannot detect it.
• To understand the influence of climate change on drivers of droughts in the region, and thereby rain-fed agriculture it is key to invest in and maintain a network of rain gauges.
• The chronic food insecurity and vulnerable economic situation of many in the region, means that even small shifts in rainfall (drought or floods) cascade and impact the already limited food supply in the Sahel. Increasing conflict and its impact on people (e.g. displacement, limiting agricultural activity and access to markets) and state fragility are also major contributors. However, food security in the Sahel is not only dictated by local factors. High global food prices exacerbate food insecurity and render the region vulnerable to future impacts of climate change on global breadbaskets.

Scientists from Switzerland, India, the Netherlands, France, the United States of America and the United Kingdom, collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the low soil moisture, both at the surface and the root zones for most crops.

Main findings

• Heat and low rainfall in West-Central Europe had far reaching impacts on a variety of sectors including human health, energy, agriculture, and municipal water supply. It was exacerbated by e.g. poor water infrastructure and leakages, and it came at a time when food and energy prices were already high resulting in compounding social and economic impacts.
• In this study, we particularly focus on the dry soils which caused severe economic and ecological impacts across the Northern Hemisphere (excluding the tropical regions) and were particularly severe in West-Central Europe. We therefore focus on these two regions, North-Hemisphere extratropics and West-Central Europe, to analyse the agricultural and ecological drought from June to August 2022.
• Observation-driven land surface models show that very low summer surface and root-zone soil moisture, such as observed in 2022, happens about once in 20 years in today’s climate in both regions.
• While the magnitude of historical trends vary between different observation-based soil moisture products, all agree that the dry conditions observed in 2022 over both regions would have been less likely to occur at the beginning of the 20th century.
• To determine the role of climate change in these observed changes, we combine the observation-based datasets with climate models and conclude that human-induced climate change increased the likelihood of the observed soil moisture drought events. The change in likelihood is larger in the observation-based data compared to the models.
• We also assessed the role of climate change in temperature and rainfall in these regions and found that the strong increase in high temperatures is the main reason for the increased drought.
• Combining all lines of evidence we find for West-Central Europe that human-induced climate change made the 2022 root zone soil moisture drought about 3-4 times more likely,  and the surface soil moisture drought about 5-6 times more likely.
• For the Northern Hemisphere extratropics, human-induced climate change made the observed soil moisture drought much more likely, by a factor of at least 20 for the root zone soil moisture and at least 5 for the surface soil moisture, but as is usually the case with hard to observe quantities, the exact numbers are uncertain.
• The models analysed also show that soil moisture drought will continue to increase with additional global warming, which is consistent with projected long-term trends in climate models as reported e.g., in the IPCC AR6.

Scientists from South Africa, Madagascar, New Zealand, India, the Netherlands, France, United States of America and the United Kingdom, collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the below-average rainfall in Southern Madagascar.

Using published peer-reviewed methods, we analysed how human-induced climate change affected the 24 month low rainfall events in the Grand Sud region of Madagascar.

Main findings

• Based on observations and climate modeling, the occurrence of poor rains as observed from July 2019 to June 2021 in Southern Madagascar has not significantly increased due to human-caused climate change. While the observations and models combine to indicate a small shift toward more droughts like the 2019-2021 event as a consequence of climate change, these trends remain overwhelmed by natural variability.
• We chose to analyse severe rainfall deficits in this study. This was because recent research found rainfall deficits were the primary driver of drought in regions of East Africa with very similar climatic properties to south-west Madagascar.
• Madagascar is one of the poorest countries of the world, with a particularly high proportion of people living below the poverty line in the south of the country. This makes it difficult for local communities to cope with any prolonged period of drought, particularly when subsistence agriculture and pastoralism in the region is rain-fed only.
• Southern Madagascar has been facing a severe food security crisis, made significantly worse by well below average rainfall from July 2019 to June 2021. This exceptional drought has affected a region with high pre-existing levels of vulnerability to food insecurity, and the impacts have been compounded by COVID-19 restrictions and pest infestations.
• The rainy seasons of both 2019/20 and 2020/21 saw just 60% of normal rainfall across the Grand Sud region. This lack of rain over the 24 months from July 2019 to June 2021 was estimated as a 1-in-135 year dry event, an event only surpassed in severity by the devastating drought of 1990-92.
• Large scale teleconnections did not significantly alter the likelihood of witnessing these exceptional rainfall deficits in southern Madagascar. While past episodes of anomalously low rainfall in the region have indeed coincided with moderate El Niño events, the severe El Niño of 1997/98 saw average levels of rain in the region, while the rainy season of 2020/21 was exceptionally dry despite coinciding with a moderate strength La Niña event.
• This result is consistent with previous research, with the IPCC’s Sixth Assessment Report concluding that any perceptible changes in drought would only emerge in this region if global mean temperatures exceed 2°C above pre-industrial levels.

Authors’ note

When we started to work on this study just two months ago Geert Jan van Oldenborgh worked with us, as always as if he was not terminally ill. He helped define the event, analysed the observational data and helped framing the study. He was not among us when it was time to check everything and draw the key conclusions. He is dearly missed not just for his wisdom, experience and integrity, but also as our friend and constant reminder why we do this.