A robust and trustworthy rainfall projection over the Indian landmass is vital for devising climate adaptation strategies. However, past studies show large inter-model spread in Indian Summer monsoon (ISM) rainfall projections thus calling for more detailed investigations on the underlying process. In the present study, we investigate this aspect using Coupled Model Intercomparison Project Phase 6 (CMIP6) model projections (Shared Socioeconomic Pathways, SSP5-8.5) and historical simulations. The Multi-Model Ensemble mean (MME) results show intensification of ISM rainfall at the end of the 21st century with ISM rainfall increasing by 1.6 +/- 0.8 mm/ day under SSP5-8.5 scenario. A moisture budget analysis for the MME further infers that the thermodynamic effect (TH) due to global warming plays a dominant role in enhancing ISM rainfall in the projections, with its dynamic counterpart (DY) assuming an additional contribution. It is also revealed that both DY and TH terms contribute to the inter-model uncertainty in ISM rainfall, but with DY dominating over the other this time. The inter-model uncertainty in DY and ISM rainfall changes is linked to inter-model spread in interhemispheric thermal contrast which in-turn depends on the diversity in Equilibrium Climate Sensitivity (ECS) and Global Mean Temperature (GMT) among the models. Intriguingly, when we remove the inter-model diversity in ECS through a GMT scaling, an Atlantic meridional surface temperature gradient, involving both land and ocean, emerges as a crucial driver in controlling the uncertainty in both DY and ISM rainfall changes, and drives largescale monsoon circulation changes over African and the Indian subcontinents.

Abstract Tropical rainfall plays a central role in the climate system, shaping ecosystems and societies. Here we show that recent tropical rainfall changes are primarily driven by spatial shifts in atmospheric circulation rather than thermodynamic processes, and cannot be explained by the “Wet Get Wetter” or “Warm Get Wetter” paradigms. Observations reveal a northward shift in precipitation with wetting in the western and northern equatorial Pacific, northern Indian region, and drying south of the equator in the Pacific and South America. These trends coincide with a La Niña-like sea surface temperature pattern, strengthened Walker circulation, Southern Ocean cooling, enhanced land-sea and inter-hemispheric thermal gradients, and intensification of the Indo-Pacific warm pool. Climate models largely miss the first three features, projecting instead a reduced equatorial Pacific sea surface temperature gradient, but capture large-scale thermal gradients and Indo-Pacific warm pool changes. We show that amplified land-sea thermal contrast and Indo-Pacific warm pool intensification reproduce the observed circulation and rainfall changes. Coupled sensitivity experiments further confirm that land warming and ongoing desertification in the Northern Hemisphere act as active drivers of current tropical hydroclimate changes, challenging ocean-centric assumptions in current climate models.

Despite the decisive role of Bay of Bengal Monsoon Depressions (MDs) in contributing to the Indian summer monsoon mean rainfall, the exact mechanisms and processes contributing to their prolonged residence over the Indian landmass remain still elusive. So, a comprehensive analysis on the factors affecting the inland penetration length of MDs after landfall over the Indian landmass, is presented here using MDs identified from Indian Meteorology Department weather reports over 3 decades (1991–2020). Exploration of large-scale atmospheric circulation features using ERA-5 reanalysis data shed new insights on the processes contributing to the maintenance and sustenance of land penetrating MDs. Notably, all Higher Inland Propagating (HIP) MDs were preceded by Mid-Tropospheric Cyclones (MTCs, with cyclonic circulation in the lower and mid-troposphere) over North-West (NW) India, with this entire region experiencing increased moisture flux convergence, thus facilitating the deep intrusion of MDs into the Indian landmass. In contrast, the Lower Inland Propagating (LIP) MDs experience dry air intrusion from the adjacent desert region, creating unfavorable moisture conditions and leading to their rapid dissipation. Intriguingly, the HIP MDs were further found to cluster with the westward propagating large-scale intraseasonal mode (i.e.,10–20 days). Using the updated GLDAS soil moisture reanalysis, it is further revealed that the precipitation caused by both the MTC, and the 10–20 days intraseasonal oscillation mode saturates the land surfaces before the arrival of MDs in the northwestern central Indian region during HIP events. In short, our results show that the presence of cyclonic vorticity over NW India, in association with the large-scale westward propagating (10–20 days) mode of variability, creates favorable conditions for the inland penetration of HIP events. Further, the results highlighting the importance of 10–20 days mode and its propensity to cluster with the land penetrating MDs, assume significance in a changing climate, as the subseasonal Indian monsoon rainfall variability is projected to increase in the future.

Abstract Wind has a strong influence on the flight characteristics, movements, energetics, demography, life-history traits and biogeography of flying animals. With climate change affecting atmospheric circulation patterns at different time scales, understanding the links between wind and animal movements is crucial for predicting its impact on flying biodiversity. Most studies on the relationship between wind and seabird movements have, however, focused on local scales, exploring birds’ perceptive sensitivity to local wind. In this study, we examine low-level wind pattern oscillations in the Southern Indian Ocean at multiple time scales to explain the local- to large-scale movements of the Amsterdam albatross. Adult individuals exhibited smooth trajectories, strongly correlated with seasonal, intra-seasonal or interannual wind oscillations. Conversely, younger individuals displayed more erratic and exploratory movements, often being swept away by eastward moving low-pressure systems at a synoptic time scale. Our results suggest that Amsterdam albatrosses can learn and adapt to the annual and monthly low-level wind climatology and interannual variability of the Southern Indian Ocean. This also highlights the importance of investigating seabird movements in relation to broader-scale wind patterns to support their conservation in a changing climate due to human activities. A robust assessment of regional circulation response to climate change for upcoming decades could help project the impact of climate change on seabird movements and mitigate its effects.

This study investigates tropical precipitation responses to anthropogenic climate change during 1979-2024 using ERA5 reanalysis, CMIP6 simulations, and targeted sensitivity experiments. While future projections often assume the direct effect of CO₂ forcing, “Wet Get Wetter” or “Warm Get Wetter” frameworks, their validity for explaining recent observed rainfall trends remains uncertain. Clausius-Clapeyron scaling and a moisture budget analysis indicate that dynamic processes dominate recent tropical rainfall responses. Observations reveal a northward precipitation shift with wetting in the western and north equatorial Pacific, northern Indian region, and drying south of the equator in the Pacific and in South America. These trends coincide with a La Niña-like SST pattern, strengthened Walker circulation, Southern Ocean cooling, enhanced land-sea and inter-hemispheric thermal gradients, and intensification of the Indo-Pacific warm pool. CMIP6 models largely miss the first three features, projecting El Niño–like SST trends, but capture thermal gradients and Indo-Pacific warm pool intensification. Regression analysis shows that amplifying land-sea and inter-hemispheric thermal contrasts, and Indo-Pacific warm pool intensification, reproduces very well the observed circulation and rainfall changes. However, coupled sensitivity experiments highlight land warming as an active driver of tropical hydroclimate changes, challenging ocean-centric assumptions in current climate models.

The Sahel is one of the most vulnerable regions to climate change. Robust estimation of future changes in the Sahel monsoon is therefore essential for effective climate change adaptation. Unfortunately, state-of-the-art climate models show large uncertainties in their projections of Sahel rainfall. In this study, we use 32 models from CMIP6 to iden-tify the sources of this large intermodel spread of Sahel rainfall. By using maximum covariance analysis, we first highlight two new key drivers of this spread during boreal summer: the interhemispheric temperature gradient and equatorial Pacific sea surface temperature (SST) changes. This contrasts with previous studies, which have focused mainly on the Northern Hemisphere rather than the global scale, and in which the Pacific Ocean has been neglected in favor of the Atlantic. Next, we unravel the physical mechanisms behind these statistical relationships. First, the modulation of the interhemispheric temperature gradient across the models leads to varying latitudinal positions of the intertropical convergence zone and, consequently, varying Sahel rainfall intensity. Second, models that exhibit less warming than the multimodel mean in the equatorial Pacific, thereby projecting a less "El Nino-like" mean state, simulate enhanced precipitation over the central Sahel in the future through modulations of the Walker circulation, the tropical easterly jet, the meridional tropospheric temperature gradient, and hence regional zonal wind shear. Finally, we show that these two indices collectively explain 62% of Sahel rainfall change uncertainty: 40% due to the interhemispheric temperature gradient and 22% through equato-rial Pacific SST.

Recently, the North Tropical Atlantic (NTA) Sea Surface Temperature (SST) anomalies emerge as a key-driver in the biennial transitions of El Niño Southern Oscillation (ENSO) and by extension of the whole ENSO-Indian Summer Monsoon (ISM) system. In this context, we utilized a suite of Coupled Model Intercomparison Project Phase 6 (CMIP6) models with the Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5) and historical simulations to investigate whether the ENSO-ISM teleconnections as well as its biennial signature undergoes significant modulations in the future warming climate as mediated through the NTA SSTs. Our results reveal a pronounced increase in NTA variability under greenhouse warming, associated with an enhanced two-way teleconnection between NTA and ENSO, while the increase of ENSO variability is more modest. There is an exaggerated signature for the previous ENSO SSTs impacting boreal spring NTA SSTs, compared to a modest enhancement in NTA forcing on the following ENSO state. However, intriguingly, this later signature of NTA damping the ENSO variability seems to strengthen steadily from the historical simulation to the SSP5-8.5, implying an enhanced NTA forcing and biennial rhythm in future projections. In consonance with this emerging NTA signal, there is a significant increase in the variability of ISM rainfall by 21st century, together with a modest strengthening of the ENSO-ISM relationships in the future warming scenarios. We also noted consistent future strengthening of a biennial signature in the ENSO-ISM teleconnection. It is further inferred that the Pacific equatorial zonal SST gradient in conjunction with the NTA relative warming act as important sources for the future intensification of this biennial signal in ENSO variability and for the inter-model spread in the projections. In contrast to this, the future intensification in ISM rainfall variability and its biennial signature are not uniquely driven by these factors.

North Tropical Atlantic Sea Surface Temperature (i.e., NTA SST) anomalies emerge as a key-driver of the whole El Niño Southern Oscillation–Indian Summer Monsoon (ENSO–ISM) system. However, as the underlying physical mechanisms are not yet well understood, this study made an attempt to have deeper insights on the role of the NTA SST variability on the ISM, ENSO and their mutual relationships. The evidences from observations and a Pi-Control coupled simulation demonstrate the pronounced biennial nature of the NTA–ENSO–ISM system and suggest the precursory role of the NTA SSTs in this biennial ENSO–ISM system. As the cause-and-effect relationships are difficult to disentangle, ensembles of short coupled sensitivity experiments are conducted by imposing observed warm (cold) SST anomalies over NTA. These 1-year simulations start from various January initial conditions corresponding to strong El Niño (La Niña) events as identified from Pi-Control and subsequently impose warm (cold) SST anomalies over the NTA region after the El Niño (La Niña) peak in January. The sensitivity experiments support the hypothesis of a key role of NTA SSTs in the reversal of the ENSO conditions through their capacitor effect. They further illustrate the nonlinear characteristics of this system as cold NTA SST perturbations are more influential than warm NTA SSTs. This non-linearity brings up new perspectives on the NTA–ENSO–ISM system, as it is further reflected in the asymmetric response in the simulated ENSO–ISM, with the cold NTA perturbations initiated from the La Niña conditions showing a stronger anomalous ISM response during boreal summer, which is in contrast with the feeble ISM response in the warm NTA perturbations experiment using the El Niño initial conditions. This non-linearity of NTA–ENSO–ISM has larger implications in a global warming scenario, as the climate variability over NTA region is projected to intensify in the future.

Robust projections of the Indian summer monsoon rainfall (ISMR) are critical as it provides 80% of the annual precipitation to more than 1 billion people who are very vulnerable to climate change. However, even over the his-torical period, state-of-the-art climate models have difficulties in reproducing the observed ISMR trends and are affected by a large intermodel spread, which questions the reliability of ISMR projections. Such uncertainty could come from inter-nal variability or model biases. Here, we study the impact of the latter on the historical forced change of ISMR in 34 mod-els from CMIP6. First, we show that models' biases over India do not significantly impact how they simulate the historical change of ISMR. However, we do find statistically significant relationships between ISMR historical forced changes and remote rainfall and temperature biases within the tropics by using a maximum covariance analysis (MCA). Our results highlight the key role of tropical Pacific sea surface temperature (SST) mean state biases as an important source of inter -model spread in the ISMR change. The physical mechanisms underlying these statistical relationships between ISMR change and the intermodel spread of Pacific SST biases are finally explored. We found that models having El Nino/ La Nina-like mean SST bias in the Pacific tend to exhibit El Nino/La Nina-like changes over the historical period, impacting ISMR through a shift in the Walker circulation and Rossby wave propagation across the Pacific.

<p>Robust projections of the Indian Summer Monsoon Rainfall (ISMR) are critical as it provides 80 % of the annual precipitation to more than one billion people who are very vulnerable to changes. However, even over the historical period, CMIP (Coupled Model Intercomparison Project) coupled models have difficulties to reproduce the observed ISMR trends and are affected by a large inter-model spread, which question the reliability of the ISMR projections. When studying climate response, three main sources of uncertainties exist : scenario uncertainties, internal variability and models bias. We study the impact of the latter on the historical response of ISMR of 34 models from CMIP6. First we show that model local biases over India do not impact significantly how they simulate the response of ISMR over the recent period. However, when we enlarge the analysis to the whole tropics and study the impact of regional and remote rainfall and SST biases on ISMR historical response by using a Maximum Covariance Analysis (MCA), we do find statistical significant relationships, which may provide observational constraints on future ISMR projections. Our results highlight the key-role of the temperature gradient errors between the arid regions surrounding India and the Arabian Sea on one hand, and of Pacific rainfall and SST biases on the other hand, as an important source of inter-model spread in the ISMR response. The physical mechanisms underlying these statistical relationships between ISMR response and the inter-model spread are finally explored.</p>

The Indian Ocean Dipole (IOD) is one of the dominant modes of variability of the tropical Indian Ocean and it has been suggested to have a crucial role in the teleconnection between the Indian summer monsoon and El Nino Southern Oscillation (ENSO). The main ideas at the base of the influence of the IOD on the ENSO-monsoon teleconnection include the possibility that it may strengthen summer rainfall over India, as well as the opposite, and also that it may produce a remote forcing on ENSO itself. The Indian Ocean has been experiencing a warming, larger than any other basins, since the 1950s. During these decades, the summer monsoon rainfall over India decreased and the frequency of Indian Ocean Dipole (IOD) events increased. In the future the IOD is projected to further increase in frequency and amplitude with mean conditions mimicking the characteristics of its positive phase. Still, state of the art global climate models have large biases in representing IOD and monsoon mean state and variability, with potential consequences for properties and related teleconnections projected in the future. This works collects a review study of the influence of the IOD on the ISM and its relationship with ENSO, as well as new results on IOD projections comparing CMIP5 and CMIP6 models.

The relationships between south Asian monsoon and northern hemisphere subtropical deserts have generated a lot of interest in recent times as both systems, despite contrasting climates, are expected to be severely affected by anthropogenic climate change. This review envisages two pathways for the monsoon–desert relationship. The first one hypothesizes a significant influence of the monsoon on subtropical deserts whereby convection over the Indian summer monsoon region induces Rossby-wave descent to its west. The second one proposes a very different perspective by emphasizing the potential role of northern hemisphere deserts on the Indian summer monsoon either through the changes of surface heating over the subtropical deserts or by dry air intrusions from arid regions into the monsoon domain. However, most current coupled climate models struggle to simulate realistically these monsoon–desert relationships due to various reasons, as documented in this chapter, calling for advances in coupled models with improved physical parameterizations.

Understanding the factors that drive the dynamics of populations of long‐lived species presents a unique challenge for conservation management. Here, we investigated long-term change in the body condition of adult northern rockhopper penguins Eudyptes moseleyi at Amsterdam Island, southern Indian Ocean, which hosts 5–10% of the global population of this endangered species. Analysis of a long‐term dataset (1994–2016), concurrent to the population's rapid decline, revealed no trend in adult northern rockhopper penguin body condition over time at the stages considered in this study, i.e. breeding and moulting. However, body condition varied between years and sexes and part of this variation was explained by environmental factors. Males were on average in better condition than females whatever the stage and individuals on average were in better condition during the moulting compared to the breeding period. The environmental conditions [sea surface temperature anomaly (SSTa), Subtropical Indian Ocean Dipole (SIOD) and Southern Annular Mode (SAM)] appeared to impact non-linearly the body condition. Overall, females were in better condition for negative values of SAM, SIOD and SSTa. The body condition of males exhibited similar but less complex and more significant patterns, with decreasing body condition for increasing SAM, SIOD and SSTa. The absence of long-term trends in male and female body condition suggests that the very low reproductive output and declining population since 1997 is probably not the result of environmental conditions during pre-breeding and pre-moult and necessitates further research into possible drivers during the breeding season.

We explore the current (1958–2005 period) and near future (2006–2050 period) teleconnections between El Niño Southern Oscillation (ENSO), Indian Ocean Basin Mode (IOBM), and Indian Ocean Dipole (IOD) as simulated in historical and Representative Concentration Pathway (RCP8.5) simulations of 32 coupled models that participated in the phase five of Coupled Model Intercomparison Project (CMIP5). A set of 16 CMIP5 models out of 32 models, which perform best to simulate tropical climate variability in recent decades, is first selected using a robust method based on the Empirical Orthogonal Function analysis for detailed analysis. Most of these models show modest capability in reproducing the seasonal cycle of ENSO types in the current period. Further, amplitude of Indian Ocean (IO) modes is overestimated by the 16 models along with large inter-model spread. Based on these results, a subset of 9 models is formed, which simulate a realistic seasonal phase-locking of ENSO for a robust assessment of future teleconnections. No significant change in El Niño amplitude is detected in near future. However, the IOBM is projected to be weaker during late spring and early summer. The IOD is projected to be stronger during boreal summer in the future relative to the current period. We also investigate if there are any changes from historical to RCP 8.5 simulations in the strength of the IO negative feedback on ENSO with a multiple linear regression approach. The IO negative feedback strengthens significantly in the RCP8.5 scenario due to the increasing role of IOBM in speeding the transition from El Niño to La Niña, despite its reduction of amplitude. In contrast, IOD loses its predictive value in the future projections.

The Indian Ocean Dipole (IOD) is one of the dominant modes of variability of the tropical Indian Ocean and it has been suggested to have a crucial role in the teleconnection between the Indian summer monsoon and El Niño Southern Oscillation (ENSO). The main ideas at the base of the influence of the IOD on the ENSO-monsoon teleconnection include the possibility that it may strengthen summer rainfall over India, as well as the opposite, and also that it may produce a remote forcing on ENSO itself. In the future, the IOD is projected to increase in frequency and amplitude with mean conditions mimicking the characteristics of its positive phase. Still, state-of-the-art global climate models have large biases in representing the mean state and variability of both IOD and ISM, with potential consequences for their future projections. However, the characteristics of the IOD and ENSO are likely to continue in a future warmer world, with persistence of their linkage.

Indian Summer Monsoon (ISM) rainfall and El Niño-Southern Oscillation (ENSO) exhibit an inverse relationship during boreal summer, which is one of the roots of ISM interannual variability and its seasonal predictability. Here we document how current climate and seasonal prediction models simulate the timing and amplitude of this ISM-ENSO teleconnection. Many Coupled General Circulation Models (CGCMs) do simulate a simultaneous inverse relationship between ENSO and ISM, though with a large spread. However, most of them show significant negative correlations before ISM, which are at odd with observations. Consistent with this systematic error, simulated Niño-3.4 Sea Surface Temperature (SST) variability has erroneous high amplitude during boreal spring and ISM rainfall variability is also too strong during the first part of ISM. The role of the Indian Ocean (IO) in modulating the ISM-ENSO relationships is further investigated using dedicated experiments with the SINTEX-F2 CGCM. Decoupled tropical Pacific and IO experiments are conducted to assess the direct relationship between ISM and IO SSTs on one hand, and the specific role of IO feedback on ENSO on the other hand. The direct effect of IO SSTs on ISM is weak and insignificant at the interannual time scale in the Pacific decoupled experiment. On the other hand, IO decoupled experiments demonstrate that El Niño shifts rapidly to La Niña when ocean–atmosphere coupling is active in the whole IO or only in its western part. This IO negative feedback is mostly active during the decaying phase of El Niño, which is accompanied by a basin-wide warming in the IO, and significantly modulates the length of ENSO events in our simulations. This IO feedback operates through a modulation of the Walker circulation over the IO, which strengthens and shifts eastward an anomalous anticyclone centered on the Philippine Sea and associated easterly wind anomalies in the equatorial western Pacific during boreal winter. In turn, these atmospheric anomalies lead to a fast ENSO turnabout via oceanic adjustement processes mediated by eastward propagating upwelling Kelvin waves. An experiment in which only the SouthEast Indian Ocean (SEIO) is decoupled, demonstrates that the equatorial SST gradient in the IO during boreal winter plays a fundamental role in the efficiency of IO feedback. In this experiment, simulated ISM-ENSO lead-lag correlations match closely the observations. This success is associated with removal of erroneous SEIO SST variability during boreal winter in the SEIO decoupled experiment. Finally, it is illustrated that most CMIP5 CGCMs exhibit similar SST errors in the SEIO during boreal winter in addition to an exagerated SEIO SST variability during boreal fall.

The low-frequency evolution of Indian rainfall mean-state and associated interannual-to-decadal variability is discussed for the last 6000 years from a multi-configuration ensemble of fully coupled global transient simulations. This period is marked by a shift of Indian Summer Monsoon Rainfall (ISMR) distribution towards drier conditions, including extremes, and a contraction of the rainy season. The drying is larger in simulations with higher horizontal resolution of the atmosphere and revised land surface hydrology. Vegetation–climate interactions and the way runoff is routed to ocean modulate the timing of the monsoon onset but have negligible effects on the evolution of seasonal rainfall amounts in our modeling framework in which carbon cycling is always active. This drying trend is accompanied by changes in ISMR interannual-to-decadal variability decreasing over north and south India but increasing over central India (20°–25° N). The ISMR interannual-to-decadal variability is decomposed into six physically consistent regimes using a clustering technique to further characterize its changes and associated teleconnections. From 6 to 3.8 kyr bp, the century-to-century modulations in the frequency of occurrence associated to the regimes are asynchronous between the simulations. Orbitally-driven trends can only be detected for two regimes over the whole 6–0 kyr bp period. These two regimes reflect increased influence of ENSO on both ISMR and Indian Ocean Dipole as the inter-hemispheric energy gradient weakens. Severe long-term droughts are also shown to be a combination of long-term drying and internally generated low-frequency modulations of the interannual-to-decadal variability.

A comprehensive analysis of the role of Indo-Pakistan arid region (IPAR) in modulating the boreal summer heavy extreme rainfall events over monsoon core zone (MCZ over Indian subcontinent) at subseasonal to daily time scales is presented. The objective is to bring new perspectives on the dynamics of such rainfall extremes. Time-lagged composite analysis shows the clustering of Monsoon Intra-Seasonal Oscillation with monsoon rainfall daily extremes. However, our results additionally bring out the distinct role of surface thermal forcing and moist processes over IPAR as another potential and significant precursor, 16-10 days in advance, causing monsoon rainfall daily extremes over MCZ. Further analysis reveals that the warming over IPAR is initially found in the northern part of the domain, 20-15 days before the rainfall events over MCZ and is triggered by subtropical-midlatitude interactions characterized by the intrusion of a midlatitude (i.e., Eurasian) atmospheric wave train into the Asian domain. Our analysis further reveals strong moist static energy (MSE) build-up over the IPAR 12 days in advance, which is initially dominated by anomalous warming in the lower atmosphere, but with an incremental contribution of low-level specific humidity as we moved forward in time towards the rainfall event. Hydrodynamic-longwave radiative teleconnections are the primary mechanism for the persistence of the surface warming and MSE buildup over IPAR after the initial intrusion of the Eurasian wave train. The persistent warming over IPAR reinforces the land-sea contrast between the Middle East and western equatorial Indian Ocean to its south, and this subsequently leads to pressure anomalies and monsoon circulation changes through geostrophic wind adjustment, thus enhancing westerlies over Arabian Sea. All these factors lead to the development of a gigantic monsoon trough over central India thus causing the rainfall extremes over MCZ through the genesis of synoptic vortices.

This study revisits the role of subtropical deserts in the Indian Summer Monsoon (ISM) system by perturbing surface albedo over the subtropical deserts, to the west of the ISM domain in different ways, using a state-of-the-art coupled model. The analysis of up-to-date satellite datasets, atmospheric re-analyses and our control coupled simulation suggests that the model broadly reproduces the radiation budgets close to re-analyses and observed datasets. However, there are large uncertainties in the top-of-atmosphere radiation budget over the Northern Hemishere (NH) subtropical desert region during boreal summer; while the model has a rather neutral radiation budget during boreal summer over the Sahara Desert, the European Centre for Medium Range Weather Forecasts Interim reanalysis show in contrast a radiative excess throughout the NH desert region and the up-to-date satellite dataset has a clear negative radiation budget over north-eastern Sahara region and over Arabian Peninsula. Taking into account these incertitudes, our key finding is that by darkening the deserts and arid regions to the west of ISM through a negative albedo perturbation in our coupled model, the length and intensity of the rainy season over the Indian region are both significantly increased with two well-defined rainfall anomaly maxima in May–June and September–October. The ISM onset is advanced by 1 month and is characterized by a rapid northward propagation of the rainfall band over the Indian domain. Reversing the sign of our artificial albedo perturbation over the deserts in the model gives an opposite response, highlighting the robust role of the subtropical deserts in the ISM system, but the amplitude of the ISM response is also significantly larger, demonstrating nonlinearity in the monsoon-desert relationship. Additional albedo perturbation experiments further demonstrate that the whole hot subtropical deserts extending across Afro-Asian continents, and including the Sahara, plays a key-role in the ISM response. Finally, the modulations of the meridional tropospheric temperature gradient along with stronger equatorial asymmetry of mean easterly shear and moisture distribution over the Indian domain are key-factors for explaining the ISM response and its nonlinearity to the albedo perturbations over the NH subtropical deserts. Further insights from moisture budget show that the nonlinearity in advection moisture tendencies manifests in nonlinearity of the ISM response.