Alessandra Giannini

We integrate long-term observations of rainfall and repeat, large-scale, nationwide household surveys of nutrition and socio-economic status to assess the vulnerability of food security to climate in Senegal. We use a mixed methods approach and a vulnerability framework to explain how it is that food security is on average lower, and more variable...

In the Sahel of West Africa, food security is a top development priority. Climate shocks threaten communities that rely on a single rainy season to grow crops and raise livestock. We exploit repeat surveys collected by the World Food Programme to quantitatively assess the year-to-year dynamics of household food security. Our methodology singles out...

There is little scientific consensus on the importance of external climate forcings—including anthropogenic aerosols, volcanic aerosols, and greenhouse gases (GHG)—relative to each other and to internal variability in dictating past and future Sahel rainfall. We address this query by relating a 3-tiered multi-model mean (MMM) over the Climate Model...

Plain Language Summary The seasonal climate outlook forum for the Sudano‐Sahelian region of West Africa convenes in middle/late April at the earliest, because the statistical models currently in use to make predictions for the July–September rainy season have little skill before then. Here we show that the North American Multimodel Ensemble (NMME),...

Poster presented at the 2019 AGU Fall Meeting. Session: A31S - Seasonal to Multiseasonal Earth System Prediction and Its Applications

Prior research has shown that dry conditions tend to persist in the Sahel when El Niño develops. Yet, during the historic 2015 El Niño, Sahel summer precipitation was anomalously high particularly in the second half of the season. This seeming inconsistency motivates a re-examination of the variability of precipitation during recent El Niño years....

Recurrent convection regimes are identified during the extended West African Monsoon (WAM) season (May–Nov) using a \(k-means\) clustering of 1980–2013 NOAA daily Outgoing Longwave Radiation (OLR), and are well reproduced in 1996–2015 ECMWF week-1 reforecasts despite systematic biases. One regime of broad drying across the Sahel in the early (May–J...

Purpose of Review Knowledge of how monsoons will respond to external forcings through the twenty-first century has been confounded by incomplete theories of tropical climate and insufficient representation in climate models. This review highlights recent insights from past warm climates and historical trends that can inform our understanding of mon...

We exploit the multi-model ensemble produced by phase 5 of the Coupled Model Intercomparison Project (CMIP5) to synthesize current understanding of external forcing of Sahel rainfall change, past and future, through the lens of oceanic influence. The CMIP5 multi-model mean simulates the twentieth century evolution of Sahel rainfall, including the m...

We propose a dynamical interpretation of model projections for an end-of-century wetting in equatorial East Africa. In the current generation of global climate models, increased atmospheric moisture content associated with warming is not the dominant process explaining the increase in rainfall, as the regional circulation is only weakly convergent...

One of the most robust remote impacts of El Niño-Southern Oscillation (ENSO) is the teleconnection to tropical North Atlantic (TNA) sea surface temperature (SST) in boreal spring. However, important questions still remain open. In particular, the timing of the ENSO-TNA relationship lacks understanding. The three previously proposed mechanisms rely...

Given the uncertainties in climate model projections of Sahel precipitation, at the northern edge of the West African Monsoon, understanding the factors governing projected precipitation changes in this semiarid region is crucial. This study investigates how long-term soil moisture changes projected under climate change may feedback on projected ch...

Prior studies have highlighted West Africa as a regional hotspot of land–atmosphere coupling. This study focuses on the large-scale influence of soil moisture variability on the mean circulation and precipitation in the West African monsoon. A suite of six models from the Global Land–Atmosphere Coupling Experiment (GLACE)-CMIP5 is analyzed. In this...

We combine socio-economic data from a large-scale household survey with historical climate data to map the climate sensitivity of availability and access dimensions of food security in Mali, and infer the ways in which at-risk communities may have been impacted by persistent climatic shift. Thirty years after 1982-1984, the period of most intense d...

The small rainfall recovery observed over the Sahel, concomitant with a regional climate warming, conceals some drought features that exacerbate food security. The new rainfall features include false start and early cessation of rainy seasons, increased frequency of intense daily rainfall, increasing number of hot nights and warm days and a decreas...

Moisture budget decomposition is performed for the Sahel (10°-20°N and 20°W-40°E) in order to understand the processes that govern regional hydroclimate variability on interannual time scales and frame them in the context of their primary ocean driver. Results show that warm conditions in the Eastern Tropical Pacific remotely force anomalously dry...

Since 1999, the increased frequency of dry conditions over East Africa, particularly during the March–May (MAM) season, has heightened concerns in a region already highly insecure about food. The underlying mechanisms, however, are still not yet fully understood. This article analyses a proxy for daily convection variations over a large region enco...

The response of the terrestrial water cycle to global warming is central to issues including water resources, agriculture and ecosystem health. Recent studies indicate that aridity, defined in terms of atmospheric supply (precipitation, P) and demand (potential evapotranspiration, E p) of water at the land surface, will increase globally in a warme...

This chapter reviews the evolution of our understanding of the causes of the late 20th century Sahel drought in the context of global climate model development. In describing, in coherent and holistic fashion, physical arguments for local and global influences on regional rainfall variability and change, it aims to make sense of current trends and...

A spatial analysis is presented that aims to synthesize the evidence for climate and social dimensions of the "regreening" of the Sahel. Using an independently constructed archival database of donor-funded interventions in Burkina Faso, Mali, Niger, and Senegal in response to the persistence of drought in the 1970s and 1980s, the spatial distributi...

The evolution of El Niño can be separated into two phases-namely, growth and mature-depending on whether the regional sea surface temperature has adjusted to the tropospheric warming in the remote tropics (tropical regions away from the central and eastern tropical Pacific Ocean). The western Sahel's main rainy season (July-September) is shown to b...

Regional information on climate change is urgently needed but often deemed unreliable. To achieve credible regional climate projections, it is essential to understand underlying physical processes, reduce model biases and evaluate their impact on projections, and adequately account for internal variability. In the tropics, where atmospheric interna...

Much scientific discussion has focused on rising greenhouse gas emissions and changing rainfall patterns in an increasingly warmer world. In fact, preventing the worst impacts of climate change on future human well-being will mean dealing with heightened flood and drought risks. The authors explain why the complex science of the shifting rainfall p...

Though public discussions of climate change are recent, they draw on older discourses. In the last decade or two, climate change impacts have been presented as a pressing concern in some places, while in others they seem less urgent. We examine the discussions of place-based climate impacts in four different regions (the Arctic, islands, deserts, a...

The unusual severity and return time of the 2005 and 2010 dry-season droughts in western Amazon is attributed partly to decadal climate fluctuations and a modest drying trend. Decadal variability of western Amazon hydroclimate is highly correlated to the Atlantic sea surface temperature (SST) north–south gradient (NSG). Shifts of dry and wet events...

Advances in our fundamental understanding of the physical climate system provided the necessary scientific underpinnings for the routine production of reliable seasonal climate forecasts and ultimately, the birth of the International Research Institute for Climate and Society (IRI). While recognizing that the successful adoption of climate informat...

Though climate change is a global process, current discussions emphasize its local impacts. A review of media representations, public opinion polls, international organization documents, and scientific reports shows that global attention to climate change is distributed unevenly, with the impacts of climate change seen as an urgent concern in some...

It is well known that the Sahel region of Africa is impacted by decadal scale variability in precipitation, driven by global sea surface temperatures. This work demonstrates that the National Center for Atmospheric Research’s Community Atmosphere Model, version 4 is capable of reproducing relationships between Sahelian precipitation variability and...

This report describes the results of a climate vulnerability mapping in Mali, West Africa. The analysis finds higher levels of vulnerability in the north, and climate projections under RCP4.5 and 8.5 suggest that vulnerability levels will increase with a southward progression over the next four decades. The study employs statistical methods such as...

Analyses of phase 5 of the Coupled Model Intercomparison Project (CMIP5) experiments show that the global monsoon is expected to increase in area, precipitation, and intensity as the climate system responds to anthropogenic forcing. Concurrently, detailed analyses for several individual monsoons indicate a redistribution of rainfall from early to l...

In the Sahel region, seasonal predictions are crucial to alleviate the impacts of climate variability on populations' livelihoods. Agricultural planning (e.g., decisions about sowing date, fertilizer application date, and choice of crop or cultivar) is based on empirical predictive indices whose accuracy to date has not been scientifically proven....

We propose a re-interpretation of the oceanic influence on the climate of the African Sahel that is consistent across observations, 20th century simulations and 21st century projections, and that resolves the uncertainty in projections of precipitation change in this region: continued warming of the global tropical oceans increases the threshold fo...

We propose a re-interpretation of the oceanic influence on the climate of the African Sahel that is consistent across observations, 20th century simulations and 21st century projections, and that resolves the uncertainty in projections of precipitation change in this region: continued warming of the global tropical oceans increases the threshold fo...

The global distribution, seasonal evolution, and underlying mechanisms for the climatological midsummer drought (MSD) are investigated using a suite of relatively high spatial and temporal resolution station observations and reanalysis data with particular focus on the Pacific coast of Central America and southern Mexico. Although the MSD of Centra...

Intra-seasonal drought episodes (extreme dry spells) are strongly linked to crop yield loss in the West African Sahel, especially when they occur at crop critical stages such as juvenile or flowering stage. This paper seeks to expose potentially predictable features in the sub-seasonal to inter-annual occurrence of “extreme dry spells” (extDS) thro...

Daily rainfall records of 39 stations spanning the different agro—climatic zones of Burkina Faso were analyzed to describe the evolution of five seasonal rainfall descriptors over time. The period from1941 to 2000, including the two most contrasted periods in the recent history of the Sahelian climate, i.e. the wet decades (1941–1970) and the dry d...

We thank many anonymous reviewers for their careful reviews and constructive suggestions in improving each paper.

We present results based on an analysis of a 2005 livelihood survey of ~2000 rural households in ~200 villages scattered across Mali, a sparsely populated, large land-locked country in West Africa, to elucidate the role of climate variability and change in shaping availability and access dimensions of food security. The Comprehensive Food Security...

Twenty-first century climate model projections show an amplification of the annual cycle in tropical precipitation with increased strength in both wet and dry seasons, but uncertainty is large and few studies have examined transition seasons. Here we analyze coupled climate model projections of global land monsoons and show a redistribution of prec...

The global monsoon system is so varied and complex that understanding and predicting its diverse behaviour remains a challenge that will occupy modellers for many years to come. Despite the difficult task ahead, an improved monsoon modelling capability has been realized through the inclusion of more detailed physics of the climate system and higher...

Twenty first century climate model projections show an amplification of the annual cycle in tropical precipitation with increased strength in both wet and dry seasons, but uncertainty is large and few studies have examined transition seasons. We analyze coupled climate model projections of global land monsoons and find a redistribution of precipita...

Application of the moist static energy framework to analyses of vertical stability and net energy in the Sahel sheds light on the divergence of projections of climate change. Two distinct mechanisms are sketched. In one, anthropogenic warming changes continental climate indirectly: warming of the oceans increases moist static energy at upper levels...

This paper focuses on one key remaining uncertainty in projections of future climate states: the projection of regional precipitation change over tropical land. It considers the specific case of the African Sahel and describes physical mechanisms of climate change in the semi-arid tropics, the margins of monsoons, sketching two possible pathways of...

In this study we explore the potential for re-insurance schemes built on regional climatic forecasts. We focus on micro-insurance contracts indexed on precipitation in 9 villages in Kenya, Tanzania (Eastern Africa) and Malawi (Southern Africa), and analyze the precipitation patterns and payouts resulting from El Niño Southern Oscillation (ENSO). Th...

Analysis of twenty-first century projections suggests an amplification of the annual cycle in tropical precipitation with enhanced wet and dry seasons and inter-hemispheric asymmetry. Studies that have included transition seasons in their analysis, e.g., for West Africa and South America, indicate weakened spring and strengthened summer precipitati...

Recurrence times for extreme drought events in the African Sahel are estimated using a classical peaks-over-threshold model. Results, which are computed for both mean seasonal rainfall and fractional area in drought, suggest that the distribution of dry extremes after about 1970 is statistically distinct from that of preceding years. This finding t...

This article was submitted without an abstract, please refer to the full-text PDF file.

This article was submitted without an abstract, please refer to the full-text PDF file.

This report is one of the deliverables for the project "Commodity Risk Management Group (ARD) seeks a qualified firm for Designing Index-Based Weather Insurance Contracts For Farmers in Central America, Terms of Reference." In this report, we document the development of eleven revised and improved standardized drought contracts, including six contr...

We review the evidence that connects drought and desertification in the Sahel with climate change past, present and future. Advances in climate modeling point to the oceans, not land, as the cause of the recent persistence of drought in the Sahel. The current generation of global climate models reproduces the spatial extent, continental in scale, a...

We describe the global climate system context in which to interpret African environmental change to support planning and implementation of policymaking action at national, regional and continental scales, and to inform the debate between proponents of mitigation v. adaptation strategies in the face of climate change. We review recent advances and c...

The outlook for Sahel precipitation in coupled simulations of the twenty-first century is very uncertain, with different models disagreeing even on the sign of the trends. Such disagreement is especially surprising in light of the robust response of the same coupled models to the twentieth-century forcings. This study presents a statistical analysi...

We describe the seasonality in the variability and predictability of Indonesian monsoonal climate, dominated by the El Niño–Southern Oscillation (ENSO) phenomenon, and interpret it in light of theories of the development of the global ENSO teleconnection which explain the evolution of the response of the tropical ocean-atmosphere to ENSO's perturba...

During 2003 and 2004 several African countries were affected by swarms of desert locust in what was the worst locust crisis in the region since 1987 – 89. Early warning systems developed by the Food and Agriculture Organization of the United Nations (FAO) were in place and alerted the international donor community of the danger of a desert locust i...

Workshop on Sahel Climate Change, Columbia University, New York, 19-21 March 2007 The Sahel transition to persistent drought in the early 1970s is an archetypal example of recent abrupt climate change. This workshop assessed the mechanisms for variability at interannual and interdecadal timescales, and discussed mechanisms of future climate change...

In recent years there has been a resurgence in modeling studies of drought in the Sahel that have conclusively demonstrated the dominant role of the oceans in pacing the interannual to interdecadal variability of climate in this semi-arid region in the 20th century. Atmosphere-only models forced with the observed record of sea surface temperature,...

Here we constitute an attempt at integrating the complexity of interactions between thermodynamic and dynamical facets of precipitation adjustments to anthropogenic forcings in the 20th century. As previously shown (Liepert et al., 2004 and Feichter et al., 2004) the aerosols in climate model simulations reduce the GHG induced increase in evaporati...

General circulation model (GCM) integrations forced by observed sea surface temperature (SST) represent the climate response to SST forcing as well as internal variability or "noise." Signal-to-noise analysis identifies the most reproducible GCM patterns of African summer precipitation related to the SST forcing. Over West Africa two of these poten...

1] The African Sahel experienced severe drying between the 1950s and the 1980s, with partial recovery since. We compare Sahel rainfall in the 20th century, pre-industrial, and increased greenhouse gases (GHG) simulations produced for the Intergovernmental Panel on Climate Change (IPCC). The simulations forced by 20th century concentrations of aeros...

The climate variability and predictability over Indonesia has been studied by using a regional climate model RegCM3 driven by a GCM ECHAM4.5 as well as the NCEP reanalysis. The model is able to simulate the seasonal and interannual variation of the regional climate, particularly the impacts of ENSO. Cross-validation against the observed precipitati...

A nine-member ensemble of simulations with a state-of-the-art atmospheric model forced only by the observed record of sea surface temperature (SST) over 1930–2000 is shown to capture the dominant patterns of variability of boreal summer African rainfall. One pattern represents variability along the Gulf of Guinea, between the equator and 10°N. It c...

The dynamical processes that contribute to the seasonal prediction of the tropical Atlantic sea-surface temperature (SST) anomalies from boreal winter into spring are explored with an atmospheric general circulation model coupled to a slab ocean. Taking advantage of the reduced-physics model that effectively isolates thermodynamic feedbacks from dy...

A comparison of rainfall variability in the semi-arid Brazilian Nordeste in observations and in two sets of model simulations leads to the conclusion that the evolving interaction between Tropical Atlantic Variability (TAV) and the El Nio-Southern Oscillation (ENSO) phenomenon can explain two puzzling features of ENSOs impact on the Nordeste: (1) t...

One dominant manifestation of Tropical Atlantic Variability (TAV) takes place in March-April-May in the form of a strong inter-hemispheric sea surface temper-ature gradient coupled to a cross-equatorial near surface atmospheric flow. The variability of this circulation pattern affects the position of the intertropical con-vergence zone and the regi...

The case is advanced that decadal variability of climate in the Pacific sector is driven by tropical atmosphere-ocean interactions and communicated to the extratropics. It is shown that tropical decadal variations in the last century could arise as a consequence of the regional subset of physics contained within an intermediate model of the El Niño...

In the last 50 years or so, the Sahel region in sub-Saharan Africa has experienced two multi-decadal wet and dry periods separated by a relatively sharp transition. The onset of the dry episode in the Sahel is associated with the start of a significant warming trend in Southern Hemisphere sea surface temperatures (SST) that persisted well into the...

We present evidence, based on an ensemble of integrations with NSIPP1 (version 1 of the atmospheric general circulation model developed at NASA's Goddard Space Flight Center in the framework of the Seasonal-to-Interannual Prediction Project) forced only by the observed record of sea surface temperature from 1930 to 2000, to suggest that variability...

The state of the tropical Atlantic climate system during the onset and development stages of an El Niño-Southern Oscillation (ENSO) event affects the strength of the ENSO teleconnection to northeastern Brazil (Nordeste) the following boreal spring. The preconditioning role of Tropical Atlantic Variability (TAV) described here advocates for the cont...

When forced with the observed record of sea surface temperature only, NSIPP, the atmospheric model developed at NASA's Goddard Space Flight Center in the framework of the Seasonal to Interannual Prediction Project, exhibits unparalleled skill at reproducing the interannual variability of northern summer precipitation over tropical Africa during 193...

The interannual variability of rainfall in the northeastern region of Brazil, or Nordeste, is known to be very strongly correlated with sea surface temperature (SST) variability, of Atlantic and Pacific origin. For this reason the potential predictability of Nordeste rainfall is high. The current generation of state-of-the-art atmospheric models ca...

The change in the location and magnitude of convection associated with Atlantic Intertropical Convergence Zone (ITCZ) is a dominant feature in the spatial expression of Tropical Atlantic Variability (TAV). However, its role in the physics of TAV is seldom discussed in the literature; indeed, the ITCZ convection is often seen merely as a passive tra...

Tropical Atlantic Variability (TAV) is dominated on interannual-to-decadal timescales by an interplay between changes in SST, wind stress, and surface heat fluxes. Its clearest manifestation usually takes place in March-April-May (MAM) in the form of a strong cross-equatorial SST gradient, which affects the position of the Intertropical Convergence...

We investigate causes of interannual variability in Atlantic Intertropical Convergence Zone (ITCZ) convection using a monthly mean global precipitation data set spanning 1979-1999. Starting from the hypothesis of two dominant influences on the ITCZ, namely, the cross-equatorial gradient in tropical Atlantic sea surface temperature (SST) and the ano...

Caribbean rainfall is affected by climate variability of Pacific and Atlantic origin, e.g. the El Nino-Southern Oscillation (ENSO) phenomenon, and variability in the North Atlantic High sea level pressure (SLP) center, respectively. During the lifetime of an ENSO cycle, the basin experiences dry and wet extremes. In the case of a warm event, the dr...

The climate of the Caribbean Islands and Central America is strongly constrained by geographical location. An important portion of the interannual variability of Caribbean rainfall can be explained by the impact on the region of the well-known large-scale patterns of Pacific and Atlantic climate variability: the El Niño-Southern Oscillation (ENSO)...

Recent developments in Tropical Atlantic Variability (TAV) identify the El Niño-Southern Oscillation (ENSO) as one of the leading factors in the interannual climate variability of the basin. An ENSO event results in Tropic-wide anomalies in the atmospheric circulation that have a direct effect on precipitation variability, as well as an indirect ef...

The El Niño-Southern Oscillation (ENSO) phenomenon and variability in the subtropical North Atlantic high sea level pressure (SLP) are known to affect rainfall in the Caribbean region. An El Niño event is associated with drier-than-average conditions during the boreal summer of year (0), and wetter-than-average conditions during the spring of year...

The goal of this dissertation is to clarify the connection between the regional scale of Caribbean rainfall variability and the large scale of the surrounding climate patterns: the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). The mechanisms by which anomalies in Caribbean climate arise are discussed: (1)the ENSO tel...