The use of a climate-type classification for assessing climate change effects in Europe from an ensemble of nine regional climate models

Making use of the Köppen–Trewartha (K–T) climate classification, we have found that a set of nine high-resolution regional climate models (RCM) are fairly capable of reproducing the current climate in Europe. The percentage of grid-point to grid-point coincidences between climate subtypes based on the control simulations and those of the Climate Research Unit (CRU) climatology varied between 73 and 82%. The best agreement with the CRU climatology corresponds to the RCM “ensemble mean”. The K–T classification was then used to elucidate scenarios of climate change for 2071–2100 under the SRES A2 emission scenario. The percentage of land grid-points with unchanged K–T subtypes ranged from 41 to 49%, while those with a shift from the current climate subtypes towards warmer or drier ones ranged from 51 to 59%. As a first approximation, one may assume that in regions with a shift of two or more climate subtypes, ecosystems might be at risk. Excluding northern Scandinavia, such regions were projected to cover about 12% of the European land area.     

Assessment of CMIP5 global model simulations and climate change projections for the 21 st century using a modified Thornthwaite climate classification

A modified Thornthwaite Climate Classification is applied to a 32-member ensemble of CMIP5 GCMs in order to 1) evaluate model performance in the historical climate and 2) assess projected climate change at the end of the 21 ^{s t} century following two greenhouse gas representative concentration pathways (RCP4.5 and RCP8.5). This classification scheme differs from the well-known Köppen approach as it uses potential evapotranspiration for thermal conditions, a moisture index for moisture conditions, and has even intervals between climate classes. The multi-model ensemble (MME) reproduces the main spatial features of the global climate reasonably well, however, in many regions the climate types are too moist. Extreme climate types, such as those found in polar and desert regions, as well as the cool- and cold-wet types of eastern North America and the warm and cool-moist types found in the southern U.S., eastern South America, central Africa and Europe are reproduced best by the MME. In contrast, the cold-dry and cold-semiarid climate types characterizing much of the high northern latitudes and the warm-wet type found in parts of Indonesia and southeast Asia are poorly represented by the MME. Regionally, most models exhibit the same sign in moisture and thermal biases, varying only in magnitude. Substantial changes in climate types are projected in both the RCP4.5 and RCP8.5 scenarios. Area coverage of torrid climate types expands by 11 % and 19 % in the RCP4.5 and RCP8.5 projections, respectively. Furthermore, a large portion of these areas in the tropics will experience thermal conditions which exceed the range of historical values and fall into a novel super torrid climate class. The greatest growth in moisture types in climate zones is among those with dry climates (moisture index values < 0) with increased areas of more than 8 % projected by the RCP8.5 MME.     

Potential impact of climate change on ecosystems of the Barents Sea Region

The EU project BALANCE (Global Change Vulnerabilities in the Barents region: Linking Arctic Natural Resources, Climate Change and Economies) aims to assess vulnerability to climate change in the Barents Sea Region. As a prerequisite the potential impact of climate change on selected ecosystems of the study area has to be quantified, which is the subject of the present paper. A set of ecosystem models was run to generate baseline and future scenarios for 1990, 2020, 2050 and 2080. The models are based on data from the Regional Climate Model (REMO), driven by a GCM which in turn is forced by the IPCC-B2 scenario. The climate change is documented by means of the Köppen climate classification. Since the multitude of models requires the effect of climate change on individual terrestrial and marine systems to be integrated, the paper concentrates on a standardised visualisation of potential impacts by use of a Geographical Information System for the timeslices 2050 and 2080. The resulting maps show that both terrestrial and marine ecosystems of the Barents region will undergo significant changes until both 2050 and 2080.     

Use of the Köppen–Trewartha climate classification to evaluate climatic refugia in statistically derived ecoregions for the People’s Republic of China

Changes in climate as projected by state-of-the-art climate models are likely to result in novel combinations of climate and topo-edaphic factors that will have substantial impacts on the distribution and persistence of natural vegetation and animal species. We have used multivariate techniques to quantify some of these changes; the method employed was the Multivariate Spatio-Temporal Clustering (MSTC) algorithm. We used the MSTC to quantitatively define ecoregions for the People’s Republic of China for historical and projected future climates. Using the Köppen–Trewartha classification system we were able to quantify some of the temperature and precipitation relationships of the ecoregions. We then tested the hypothesis that impacts to environments will be lower for ecoregions that retain their approximate geographic locations. Our results showed that climate in 2050, as projected from anthropogenic forcings using the Hadley Centre HadCM3 general circulation model, were sufficient to create novel environmental conditions even where ecoregions remained spatially stable; cluster number was found to be of paramount importance in detecting novelty. Continental-scale analyses are generally able to locate potentially static ecoregions but they may be insufficient to define the position of those reserves at a grid cell-by-grid cell basis.     

Future changes of the terrestrial ecosystem based on a dynamic vegetation model driven with RCP8.5 climate projections from 19 GCMs

Future changes of terrestrial ecosystems due to changes in atmospheric CO₂ concentration and climate are subject to a large degree of uncertainty, especially for vegetation in the Tropics. Here, we evaluate the natural vegetation response to projected future changes using an improved version of a dynamic vegetation model (CLM-CN-DV) driven with climate change projections from 19 global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The simulated equilibrium vegetation distribution under historical climate (1981–2000) has been compared with that under the projected future climate (2081–2100) scenario for Representative Concentration Pathway 8.5 (RCP8.5) to qualitatively assess how natural potential vegetation might change in the future. With one outlier excluded, the ensemble average of vegetation changes corresponding to climates of 18 GCMs shows a poleward shift of forests in northern Eurasia and North America, which is consistent with findings from previous studies. It also shows a general “upgrade” of vegetation type in the Tropics and most of the temperate zones, in the form of deciduous trees and shrubs taking over C3 grass in Europe and broadleaf deciduous trees taking over C4 grasses in Central Africa and the Amazon. LAI and NPP are projected to increase in the high latitudes, southeastern Asia, southeastern North America, and Central Africa. This results from CO₂ fertilization, enhanced water use efficiency, and in the extra-tropics warming. However, both LAI and NPP are projected to decrease in the Amazon due to drought. The competing impacts of climate change and CO₂ fertilization lead to large uncertainties in the projection of future vegetation changes in the Tropics.     

A short update on Koeppen climate shifts in Europe between 1901 and 2003

The question is investigated how far global warming in the period 1901–2003 will affect the region of Europe. For this purpose, changes of the climate zones that exist according to Koeppen will be analysed. The trends and outliers in terms of expansion and location of individual climate types are used as statistical indicators of climate change. The most important results of this study are: a) a significant increase of the extension of the climate types BS and Cr; b) a significant decrease of the extension of the climate types Dc and Ec; c) the largest changes are observed within the last two decades. These changes are discussed in relation to the mean conditions of temperature and precipitation. Moreover, significant correlations between the area extensions of climate types and the NAO index could be found.     

Changes in climate classification and extreme climate indices from a high-resolution future projection in Korea

We investigate the future changes in the climate zone and six extreme temperature indices in Korea, using the 20-km high-resolution atmospheric general circulation model (MRI-AGCM3.1S). The Trewartha and K?ppen climate classification schemes are applied, and four summer-based extreme temperature indices (i.e., summer days, tropical nights, growing degree days, and cooling degree days (CDD) and two winter-based indices (frost days and heating degree days (HDD) are analyzed. To represent significantly the change in threshold indices, the monthly mean bias is corrected in model. The model result reasonably captures the temporal and spatial distribution of the present-day extreme temperatures associated with topography. It was found that in the future climate, the area of the subtropical climate zone in Korea expands northward and increases by 21% under the Trewartha classification scheme and by 35% under the K?ppen classification scheme. The spatial change in extreme climate indices is significantly modulated by geographical characteristics in relation to land-ocean thermal inertia and topographical effects. The change is manifested more in coastal regions than in inland regions, except for that in summer days and HDD. Regions with higher indices in the present climate tend to reveal a larger increase in the future climate. The summer-based indices display an increasing trend, while the winter-based indices show a decreasing trend. The most significant increase is in tropical nights (+452%), whereas the most significant decrease is in HDD (?25%). As an important indicator of energy-saving applications, the changes in HDD and CDD are compared in terms of the frequency and intensity. The future changes in CDD reveal a higher frequency but a lower temperature than those in HDD. The more frequent changes in CDD may be due to a higher and less dispersed occurrence probability of extreme temperatures during the warm season. The greater increase in extreme temperature events during the summer season remains an important implication of projecting future changes in extreme climate events.     

闪电活动的气候学特征研究进展

综述了闪电活动与气候和气候变化相关研究的一系列最新进展。这些研究表明全球闪电活动可以通过卫星光学方法、地面的单站舒曼共振法以及低频多站时差法进行观测,其结果指出全球闪电密度高值区主要分布在海岸地区、山地地区、中尺度气旋多发地区以及热带辐合带的辐合区内,大陆、海岛、沿海地区所发生的闪电占全球的88%,全球3个闪电密度极大值依次出现在赤道地区的非洲刚果、南美洲大陆和东南亚。大量的研究结果表明全球闪电活动是与气候和气候变化相关的,在日、5d、季、半年、年、ENSO、10a多个时间尺度上,闪电活动对温度做出了一定的正响应,但在更长时间尺度上这种敏感性似乎是减弱的。闪电活动因易于被持续监测而可以作为监测气候一些重要参数变化的有利工具。闪电活动是氮氧化物(NOx)的重要产生源,这与臭氧等温室气体以及地球辐射之间存在密切关系。在短时间尺度上,对流层上层水汽和全球闪电活动之间存在非常好的相关性。气溶胶对雷暴以及闪电活动的影响还不明确。气候变化与雷暴和闪电活动之间的相互耦合机制还有待于更多的观测和深入的研究。     

Projected Changes in Kppen Climate Types in the 21st Century over China

Future changes in the climate regimes over China as measured by the Kppen climate classification are reported in this paper. The analysis is based on a high-resolution climate change simulation conducted by a regional climate model (the Abdus Salam International Center for Theoretical Physics (ICTP) RegCM3) driven by the global model of Center for Climate System Research (CCSR)/National Institute for Environment Studies (NIES)/Frontier Research Center for Global Change (FRCGC) MIROC3.2_hires (the Model for Interdisciplinary Research on Climate) under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario. Validation of the model performances is presented first. The results show that RegCM3 reproduces the present-day distribution of the Kppen climate types well. Significant changes of the types are found in the future over China, following the simulated warming and precipitation changes. In southern China, the change is characterized by the replacement of subtropical humid (Cr) by subtropical winter-dry (Cw). A pronounced decrease of the cold climate types is found over China, e.g., tundra (Ft) over the Tibetan Plateau and sub-arctic continental (Ec) over northeast China. The changes are usually greater in the end compared with the middle of the 21st century.     

Projections of climate change impacts on central America tropical rainforest

Tropical rainforest plays an important role in the global carbon cycle, accounting for a large part of global net primary productivity and contributing to CO₂ sequestration. The objective of this work is to simulate potential changes in the rainforest biome in Central America subject to anthropogenic climate change under two emissions scenarios, RCP4.5 and RCP8.5. The use of a dynamic vegetation model and climate change scenarios is an approach to investigate, assess or anticipate how biomes respond to climate change. In this work, the Inland dynamic vegetation model was driven by the Eta regional climate model simulations. These simulations accept boundary conditions from HadGEM2-ES runs in the two emissions scenarios. The possible consequences of regional climate change on vegetation properties, such as biomass, net primary production and changes in forest extent and distribution, were investigated. The Inland model projections show reductions in tropical forest cover in both scenarios. The reduction of tropical forest cover is greater in RCP8.5. The Inland model projects biomass increases where tropical forest remains due to the CO₂ fertilization effect. The future distribution of predominant vegetation shows that some areas of tropical rainforest in Central America are replaced by savannah and grassland in RCP4.5. Inland projections under both RCP4.5 and RCP8.5 show a net primary productivity reduction trend due to significant tropical forest reduction, temperature increase, precipitation reduction and dry spell increments, despite the biomass increases in some areas of Costa Rica and Panama. This study may provide guidance to adaptation studies of climate change impacts on the tropical rainforests in Central America.     

Impact of projected SST changes on summer rainfall in southeastern South America

Recent studies have shown that global warming and associated sea-surface temperature (SST) changes may trigger an important rainfall increase in southeastern South America (SESA) during the austral summer (December–January–February, DJF). The goal of this paper is to provide some insight into processes which may link global and SESA changes. For this purpose, a “two-way nesting” system coupling interactively the regional and global versions of the LMDZ4 atmospheric model is used to study the response to prescribed SST changes. The regional model is a variable-grid version of the global model, with a zoom focused over South America. An ensemble of simulations forced by distinct patterns of DJF SST changes has been carried out using a decomposition of full SST changes into their longitudinal and latitudinal components. The full SST changes are based on projections for the end of the twenty-first century from a multi-model ensemble of WCRP/CMIP3. Results confirm the presence of a major rainfall dipole structure, characterized by an increase in SESA and a decrease in the South Atlantic Convergence Zone region. Rainfall changes found in the WCRP/CMIP3 models are largely explained as a response of this dipole structure to the zonally-asymmetric (or longitudinal) component of SST changes. The rainfall response to the zonal-mean (or latitudinal) SST changes (including the global warming signal itself) shows an opposite contribution. The processes explaining the role of zonally-asymmetric SST changes involve remote effects of SST warming over the equatorial Indian and Pacific oceans inducing an atmospheric wave-train extended across the South Pacific into South America.     

Atmosphere-land surface interactions and their influence on extreme rainfall and potential abrupt climate change over southern Africa

In a changing climate, changes in rainfall variability and, in particular, extreme rainfall events are likely to be highly significant for environmentally vulnerable regions such as southern Africa. It is generally accepted that sea-surface temperatures play an important role in modulating rainfall variability, thus the majority work to date has focused on these mechanisms. However past research suggests that land surface processes are also critical for rainfall variability. In particular, work has suggested that the atmosphere-land surface feedback has been important for past abrupt climate changes, such as those which occurred over the Sahara during the mid-Holocene or, more recently, the prolonged Sahelian drought. Therefore the primary aim of this work is to undertake idealised experiments using both a regional and global climate model, to test the sensitivity of rainfall variability to land surface changes over a location where such abrupt climate changes are projected to occur in the future, namely southern Africa. In one experiment, the desert conditions currently observed over southwestern Africa were extended to cover the entire subcontinent. This is based on past research which suggests a remobilisation of sand dune activity and spatial extent under various scenarios of future anthropogenic global warming. In the second experiment, savanna conditions were imposed over all of southern Africa, representing an increase in vegetation for most areas except the equatorial regions. The results suggest that a decrease in rainfall occurs in the desert run, up to 27% of total rainfall in the regional model (relative to the control), due to a reduction in available moisture, less evaporation, less vertical uplift and therefore higher near surface pressure. This result is consistent across both the regional and global model experiments. Conversely an increase in rainfall occurs in the savanna run, because of an increase in available moisture giving an increase in latent heat and therefore surface temperature, increasing vertical uplift and lowering near surface pressure. These experiments, however, are only preliminary, and form the first stage of a wider study into how the atmosphere-land surface feedback influences rainfall extremes over southern Africa in the past (when surface i.e. vegetation conditions were very different) and in the future under various scenarios of future climate change. Future work will examine how other climate models simulate the atmosphere-land surface feedback, using more realistic vegetation types based on past and future surface conditions.     

Global climate changes and moisture conditions in the intracontinental arid zones

In order to estimate a transient response of the local hydrological cycle and vegetation cover in the African monsoon area to global climate changes, a simple two-dimensional water vapor transport model coupled with a carbon cycle model for the soil was used. The key difference from other models is that we take into account a positive feedback between the precipitation and development of the vegetation root system in the underlying surface. As our calculation shows, this feedback is responsible for a long-term transient response of local hydrological cycles to the global temperature changes. In the case of a four component vegetation system - tropical forests, savannah, semi desert and desert, (and 2 °C ocean surface water warming), a new steady-state is reached in about 1500 years.In previous works of other authors, the increase of summer precipitations during Holocene or Last Interglacial could be explained only as a result of the surface temperature increase in the intracontinental parts of Africa. However, from paleodata indicates, the temperature in the intracontinental regions of Africa rather decreased during warm epochs of geological past: Holocene optimum, Last Interglacial and middle Pliocene climatic optimum. Our simple model simulations agree with both paleoprecipitation and paleotemperature data.     

Climate change hotspots in the CMIP5 global climate model ensemble

We use a statistical metric of multi-dimensional climate change to quantify the emergence of global climate change hotspots in the CMIP5 climate model ensemble. Our hotspot metric extends previous work through the inclusion of extreme seasonal temperature and precipitation, which exert critical influence on climate change impacts. The results identify areas of the Amazon, the Sahel and tropical West Africa, Indonesia, and the Tibetan Plateau as persistent regional climate change hotspots throughout the 21st century of the RCP8.5 and RCP4.5 forcing pathways. In addition, areas of southern Africa, the Mediterranean, the Arctic, and Central America/western North America also emerge as prominent regional climate change hotspots in response to intermediate and high levels of forcing. Comparisons of different periods of the two forcing pathways suggest that the pattern of aggregate change is fairly robust to the level of global warming below approximately 2 °C of global warming (relative to the late-20th-century baseline), but not at the higher levels of global warming that occur in the late-21st-century period of the RCP8.5 pathway, with areas of southern Africa, the Mediterranean, and the Arctic exhibiting particular intensification of relative aggregate climate change in response to high levels of forcing. Although specific impacts will clearly be shaped by the interaction of climate change with human and biological vulnerabilities, our identification of climate change hotspots can help to inform mitigation and adaptation decisions by quantifying the rate, magnitude and causes of the aggregate climate response in different parts of the world.     

Application of the K?ppen classification for climatic zoning in the state of Minas Gerais, Brazil

The knowledge of the climatic conditions of a region is crucial for its agricultural development. It is also extremely important for understanding the fact that certain cultures have to develop under prevailing temperature and humidity conditions and assist in the adoption of a suitable irrigation technique, as well as its management and operationalization. The K?ppen system of climate classification is widely used for the identification of homogeneous climate zones as it considers only rainfall and temperature as the meteorological elements for classification. For this study, we used climatic databases of rainfall and temperature in a raster format, with a spatial resolution of 30″ of arc (an approximate area of 0.86?km²?pixel^?1), from 1961 to 1990. Through geoprocessing techniques, we obtained a map of climatic classification for the state of Minas Gerais. We found that the state has the following three major climatic groups: A, B and C, which correspond to tropical rainy, dry and warm temperate climates, respectively. The climate classes obtained were Aw, Am, BSh, Cwa and Cwb, with Aw, Cwa and Cwb classes occupying 99.89% of the territorial area of the state. The validation of the results showed a satisfactory agreement, with 93.75% reliability.     

ENSO nonlinearity in a warming climate

The El Niño Southern Oscillation (ENSO) is known as the strongest natural inter-annual climate signal, having widespread consequences on the global weather, climate, ecology and even on societies. Understanding ENSO variations in a changing climate is therefore of primordial interest to both the climate community and policy makers. In this study, we focus on the change in ENSO nonlinearity due to climate change. We first analysed high statistical moments of observed Sea Surface Temperatures (SST) timeseries of the tropical Pacific based on the measurement of the tails of their Probability Density Function (PDF). This allows defining relevant metrics for the change in nonlinearity observed over the last century. Based on these metrics, a zonal “see-saw” (oscillation) in nonlinearity patterns is highlighted that is associated with the change in El Niño characteristics observed in recent years. Taking advantage of the IPCC database and the different projection scenarios, it is showed that changes in El Niño statistics (or “flavour”) from a present-day climate to a warmer climate are associated with a significant change in nonlinearity patterns. In particular, in the twentieth century climate, the “conventional” eastern Pacific El Niño relates more to changes in nonlinearity than to changes in mean state whereas the central Pacific El Niño (or Modoki El Niño) is more sensitive to changes in mean state than to changes in nonlinearity. An opposite behaviour is found in a warmer climate, namely the decreasing nonlinearity in the eastern Pacific tends to make El Niño less frequent but more sensitive to mean state, whereas the increasing nonlinearity in the west tends to trigger Central Pacific El Niño more frequently. This suggests that the change in ENSO statistics due to climate change might result from changes in the zonal contrast of nonlinearity characteristics across the tropical Pacific.     

The exposure of global base metal resources to water criticality,scarcity and climate change

Mining operations are vital to sustaining our modern way of life and are often located in areas that have limited water supplies or are at an increased risk of the effects of climate change. However, few studies have considered the interactions between the mining industry and water resources on a global scale. These interactions are often complex and site specific, and so an understanding of the local water contexts of individual mining projects is required before associated risks can be adequately assessed. Here, we address this important issue by providing the first quantitative assessment of the contextual water risks facing the global base metal mining industry, focusing on the location of known copper, lead, zinc and nickel resources.The relative exposure of copper, lead-zinc and nickel resources to water risks were assessed by considering a variety of spatial water indices, with each providing a different perspective of contextual water risks. Provincial data was considered for water criticality (CRIT), supply risk (SR), vulnerability to supply restrictions (VSR) and the environmental implications (EI) of water use. Additionally, watershed or sub-basin scale data for blue water scarcity (BWS), the water stress index (WSI), the available water remaining (AWaRe), basin internal evaporation recycling (BIER) ratios and the water depletion index (WDI) were also considered, as these have particular relevance for life cycle assessment and water footprint studies. All of the indices indicate that global copper resources are more exposed to water risks than lead-zinc or nickel resources, in part due to the large copper endowment of countries such as Chile and Peru that experience high water criticality, stress and scarcity. Copper resources are located in regions where water consumption is more likely to contribute to long-term decreases in water availability and also where evaporation is less likely to re-precipitate in the same drainage basin to cause surface-runoff or groundwater recharge.The global resource datasets were also assessed against regional Köppen-Geiger climate classifications for the observed period 1951–2000 and changes to 2100 using the Intergovernmental Panel on Climate Change’s A1FI, A2, B1 and B2 emission scenarios. The results indicate that regions containing copper resources are also more exposed to likely changes in climate than those containing lead-zinc or nickel resources. Overall, regions containing 27–32% (473–574 Mt Cu) of copper, 17–29% (139–241 Mt Pb + Zn) of lead-zinc and 6–13% (19–39 Mt Ni) of nickel resources may have a major climate re-classification as a result of anthropogenic climate change. A further 15–23% (262–412 Mt) of copper, 23–32% (195–270 Mt) of lead-zinc and 29–32% (84–94 Mt) of nickel are exposed to regional precipitation or temperature sub-classification changes. These climate changes are likely to alter the water balance, water quality and infrastructure risks at mining and mineral processing operations. Effective management of long-term changes to mine site water and climate risks requires the further adoption of anticipatory risk management strategies.     

Projected changes in the physical climate of the Gulf Coast and Caribbean

As the global climate warms due to increasing greenhouse gases, the regional climate of the Gulf of Mexico and Caribbean region will also change. This study presents the latest estimates of the expected changes in temperature, precipitation, tropical cyclone activity, and sea level. Changes in temperature and precipitation are derived from climate model simulations produced for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4), by comparing projections for the mid- and late-21st century to the late 20th century and assuming a “middle-of-the-road” scenario for future greenhouse gas emissions. Regional simulations from the North America Regional Climate Change Program (NARCCAP) are used to corroborate the IPCC AR4 rainfall projections over the US portion of the domain. Changes in tropical cyclones and sea level are more uncertain, and our understanding of these variables has changed more since IPCC AR4 than in the case of temperature and precipitation. For these quantities, the current state of knowledge is described based on the recent peer-reviewed literature.     

Changes in weather and climate extremes: phenomenology and empirical approaches

The terms “weather extremes” and “climate extremes” are widely used in meteorology, often in relation to climate change. This paper reviews the empirical investigations into parallel changes in extreme events and climate change published in recent years and looks at their relevance for the global energy system. Empirical investigation into the correlation of extremes with global warming covers five groups: changes in temperature, precipitation, wind (storm) extremes, tropical and extra-tropical circulation phenomena. For temperature extremes, extensive analyses demonstrate that extreme hot days and nights will likely become more frequent, and extreme cold days and nights less frequent. Intense precipitation events will likely become more frequent in most continental regions. Scientific confidence in the trends of the frequency, duration, and intensity of tropical cyclones, is still low. A poleward shift is observed for extratropical cyclones, whereas no convincing tendencies of many smaller-scale phenomena, for example, tornados, or hail, can yet be detected. All these extremes have serious implications for the energy sector.     

A global perspective on African climate

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 current challenges in African climate research and exploit our physical understanding of variability and trends to shape our outlook on future climate change. We classify the various mechanisms that have been proposed as relevant for understanding variations in African rainfall, emphasizing a “tropospheric stabilization” mechanism that is of importance on interannual time scales as well as for the future response to warming oceans. Two patterns stand out in our analysis of twentieth century rainfall variability: a drying of the monsoon regions, related to warming of the tropical oceans, and variability related to the El Niño–Southern Oscillation. The latest generation of climate models partly captures this recent continent-wide drying trend, attributing it to the combination of anthropogenic emissions of aerosols and greenhouse gases, the relative contribution of which is difficult to quantify with the existing model archive. The same climate models fail to reach a robust agreement regarding the twenty-first century outlook for African rainfall, in a future with increasing greenhouse gases and decreasing aerosol loadings. Such uncertainty underscores current limitations in our understanding of the global climate system that it is necessary to overcome if science is to support Africa in meeting its development goals.