In a rapidly changing climate, evidence-based decision-making benefits from up-to-date and timely information. Here we compile monitoring datasets (published at https://doi.org/10.5281/zenodo.15639576; Smith et al., 2025a) to produce updated estimates for key indicators of the state of the climate system: net emissions of greenhouse gases and short-lived climate forcers, greenhouse gas concentrations, radiative forcing, the Earth's energy imbalance, surface temperature changes, warming attributed to human activities, the remaining carbon budget, and estimates of global temperature extremes. This year, we additionally include indicators for sea-level rise and land precipitation change. We follow methods as closely as possible to those used in the IPCC Sixth Assessment Report (AR6) Working Group One report. The indicators show that human activities are increasing the Earth's energy imbalance and driving faster sea-level rise compared to the AR6 assessment. For the 2015–2024 decade average, observed warming relative to 1850–1900 was 1.24 [1.11 to 1.35] °C, of which 1.22 [1.0 to 1.5] °C was human-induced. The 2024-observed best estimate of global surface temperature (1.52 °C) is well above the best estimate of human-caused warming (1.36 °C). However, the 2024 observed warming can still be regarded as a typical year, considering the human-induced warming level and the state of internal variability associated with the phase of El Niño and Atlantic variability. Human-induced warming has been increasing at a rate that is unprecedented in the instrumental record, reaching 0.27 [0.2–0.4] °C per decade over 2015–2024. This high rate of warming is caused by a combination of greenhouse gas emissions being at an all-time high of 53.6±5.2 Gt CO2e yr−1 over the last decade (2014–2023), as well as reductions in the strength of aerosol cooling. Despite this, there is evidence that the rate of increase in CO2 emissions over the last decade has slowed compared to the 2000s, and depending on societal choices, a continued series of these annual updates over the critical 2020s decade could track decreases or increases in the rate of the climatic changes presented here.

Since the last couple of decades, western India has been experiencing persistent, intense rain episodes frequently during the summer monsoon season. Most of the pluvial episodes are accompanied by diverse convective systems modulated by the background monsoon circulation. As the climate warms, the changing environmental conditions affect the nature and intensity of the weather systems. This study discusses the evolving large-scale conditions under global warming, along with the recent changes in the occurrence of a special class of heavy-precipitating synoptic systems, the mid-tropospheric cyclones (MTCs). Observed particularly over the Northeast Arabian Sea, MTCs exhibit pronounced mid-level vorticity with minimal signature at the surface. Observational results suggest significant increasing trends in deep convection and heavy precipitation over western India during the summer monsoon season. The background conditions are dominated by warming in the Arabian Sea and the Indian Ocean, accompanied by strengthening of cyclonic circulation and ascending motion at mid-level over western India. An objective vortex identification using reanalysis dataset indicates a rise in the seasonal frequency and duration of heavy precipitating mid-tropospheric cyclonic systems over western India, resulting in a significant amplification of precipitation from these systems. Furthermore, outputs from seven global climate models of the Coupled Model Intercomparison Project Phase 6 (CMIP6) are used to assess the potential changes in the large-scale patterns conducive to the development and sustenance of mid-tropospheric cyclonic systems over western India with continued global warming following the Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5) scenario. The models project stronger moisture transport over western India that triggers greater moisture convergence along the Indian west coast, aided by elevated water vapor content due to local sea surface warming. We also notice an increase in seasonal mean ascent and relative vorticity, particularly, at the middle troposphere, thereby creating a favorable setting for the occurrence of MTCs and the deep convective clouds in the late 21st century. This interplay between circulation–convection–precipitation on different spatiotemporal scales over the South Asian monsoon domain carries significant implications for assessment of regional hydrological extremes in a warming climate.

The Indian Ocean Dipole (IOD) significantly influences tropical precipitation patterns, with its positive phase triggering severe floods and droughts in Indian Ocean rim countries. These climate extremes are projected to intensify under global warming. However, how the IOD will modulate the tropical precipitation and ecosystem response under warming climate remains unknown. Here, we uncover contrasting precipitation response to IOD seasonality and highlight the pivotal role of boreal summer monsoon circulation. An early-onset of the IOD during boreal spring enhances its intensity through non-linear interactions with the summer monsoon circulation, amplifying tropical precipitation responses. Conversely, a late-onset IOD exhibits weaker ocean-atmosphere feedbacks, resulting in reduced amplitude, early decay, and drought-like conditions across the tropics. Enhanced precipitation during early-onset IOD enhances the gross primary productivity over the Asian landmass, which has significant implications for food security in a region that supports the majority of the global population. Meanwhile, marine productivity in the Arabian Sea shows a substantial decline during both early and late IOD events, threatening one of the world's most productive oceanic ecosystems. Using coupled climate model projections, we demonstrate that tropical precipitation is likely to enhance with early-IOD under greenhouse warming. These findings have critical implications for the hydrological cycle, ecosystem and, socio-economic resilience in Indian Ocean rim countries.

Deciphering the rainfall trends over the Western Ghats situated along the west coast of India has been the subject of several recent studies. However, less attention is rendered, particularly to understanding the spatial characteristics of atmospheric features associated with widespread and elevation-dependent extreme rainfall occurrences over this region and this study intends to provide some insights into this aspect. This study observes a rising trend in extreme rainfall events over the Western Ghats during the 1979–2020 period, consistent with earlier investigations. The extreme rainfall events on the windward side located below and above 500 m above sea level exhibit different background circulation signatures, such as mean wind speeds of low-level jets and moist static stability. The extreme rainfall events seen below [above] 500 m above sea level occur in the backdrop of mesoscale [large-scale] monsoon circulation. A Froude number analysis further elucidates the importance of Western Ghats foothill topography in complementing the development and spatial segregation of extreme rainfall occurrences.

Arctic sea-ice decline has been accelerating under greenhouse warming. In this study, we investigate the tropical precipitation response to declining Arctic sea-ice using observations and climate model simulations. Observational evidence and idealized model experiments in which the Arctic becomes seasonally ice free under greenhouse warming reveal association between the Arctic sea-ice decline and intense precipitation events (IPEs) over South Asia. The enhanced Arctic sea-ice melt increases the mid-latitude waviness and intensifies the circumglobal teleconnection-like pattern and strengthens the subtropical high over East Asia. This, together with a La-Nina like response in the Pacific enhances mean summer monsoon precipitation over South Asia. Additionally, the enhanced energy in the tropics and the anomalous mid-latitude intrusions due to the Arctic sea-ice melt provide a conducive environment for moisture convergence and intense summer monsoon precipitation events over South Asia. Our findings reveal that, in a future warming scenario, Arctic sea-ice melt is likely a contributing factor for the amplified mean and IPEs over the South Asian region.

Mean sea level rise (MSLR) and weather extremes can drive extreme sea level (ESL) variations locally. In the Indian Ocean, ESL estimates under global warming are either absent or limited by MSLR alone or biased storm surge model simulations. Using tide gauge, machine learning, and numerical models, we identify a rapid emergence of ESL in the Indian Ocean, particularly in the equatorial region compared to off-equatorial areas. Equatorial islands will experience the one-in-a-hundred-year ESL (ESL 100 ) of the present-day annually by 2030-40 under a high-emission scenario, with delay until 2050 for the Arabian Sea coastline and the south subtropical regions. MSLR will mainly contribute to future ESL changes, with tide and surges contributing less than 10%. A median rise of 60–80 cm in ESL is anticipated by 2100, demanding coastal planning and climate adaptation strategies for a resilient coastal population.

Monsoon precipitation is the critical source of freshwater for some of the world’s most densely populated areas, yet extreme precipitation events in these regions present significant risks, including devastating floods and damage to agriculture and infrastructure. Recent events, such as the severe flooding and landslides during the 2023 North India monsoon and the 2022 Pakistan floods,1For example, https://foreignpolicy.com/2022/09/01/pakistan-flooding-crisis-climate-change-governance/ and https://www.theguardian.com/world/2023/jul/10/india-floods-new-delhi-rain-record-deaths (last assessed 30 September 2024).1 underscore the pressing need to better understand and predict these hazards. While the science of monsoons has been studied for decades, with theories centered on global dynamics and moist energy budgets to explain the zonal mean state of monsoon and factors leading to regional differences, one key theme of all these analyses is the spatiotemporal variability of rainfall from the dry to wet seasons. A key challenge is understanding and predicting extreme rainfall incidents during monsoon seasons to help mitigate dire undesired consequences.In the past two decades, nonlinear system dynamics has emerged as a novel and promising approach in climate science research, with complex network analysis becoming one of the most rapidly developing methods. Complex networks offer a powerful tool to uncover interactions among various geographic locations and teleconnection patterns, providing new insights into the behavior of monsoon systems. Since its origin in graph theory, network dynamics has evolved to focus on metrics such as centrality and community detection, which when applied to monsoon precipitation, particularly extremes, reveal coherent structures that were previously unidentified. Notably, network communities have shown strong associations with the major monsoon regions, offering fresh perspectives on monsoon dynamics.This paper synthesizes recent studies on monsoon precipitation, particularly those employing network metrics to understand key physical processes. While both statistical and dynamical models continue to struggle with predicting extreme monsoon precipitation, complex network analysis has identified new predictors related to global monsoon teleconnection patterns. These predictors address non-stationarities caused by climate variability, presenting opportunities to enhance monsoon predictions. Nonlinear system science thus holds significant potential for deepening our understanding of the spatiotemporal variability of global monsoon and extreme weather events.Finally, this paper outlines a future research agenda aimed at addressing key knowledge gaps. These include expanding the regions of study to explore region-to-region teleconnections, enhancing the physical understanding of network metrics, applying coupled networks, investigating the interannual and interdecadal variability of monsoons, and utilizing network diagnostics of climate model evaluation.

The practice of initialized subseasonal, seasonal and decadal climate prediction has matured considerably in recent years, with real-time subseasonal and decadal multi-system ensembles joining those established previously for the seasonal to multi-seasonal range. However, substantial scientific, modelling, and informational challenges remain that must be overcome in order to more fully realize the potential for such predictions to serve societal needs. This presentation will examine five such challenges that the World Climate Research Programme’s Working Group on Subseasonal to Interdecadal Prediction (WGSIP) has identified as crucial for further advancing capabilities for translating the inherent predictability of the Earth system into actionable predictive information. Surmounting these challenges will bring nearer an envisaged future in which global users have access to such information specific to individual needs, across Earth system components and on a continuum of time scales, with degrees of confidence, limitations and uncertainties clearly indicated, as well as tools to guide optimal actions.

For the first time in the latest Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), water has been the focus of dedicated chapters in both Working Group 1 (Chapter 8) and 2 (Chapter 4). Nevertheless, we argue here that water has not yet received the full attention it deserves from both scientists and policymakers for several reasons. Firstly, the historical focus on temperature change has been further increased with the use of global warming levels motivated by an aim to be consistent with current policy framings. Secondly, an increasing attention paid to extreme weather has sometimes overshadowed longer time-scale changes such as the aridification of an increasing fraction of arable land and the increasing variability of the water cycle from month to month, season to season, and year to year that also yield cascading impacts on all water use sectors. Thirdly, a stronger focus is needed on understanding the effectiveness of current and future adaptation strategies in reducing water-related climate risks. Finally, the role of water has not been adequately recognized in the assessment of mitigation strategies although the compliance with the Paris Agreement and the current pledges all require a massive deployment of land-based strategies whose feasibility and efficiency heavily depend on water resources. It is thus essential to develop a more integrated approach to water and climate change, that would allow scientists and policymakers to “close the loop” between mitigation options, water cycle changes, hydrological impacts and adaptation.

Accumulation of water vapor in the upper troposphere/lower stratosphere (UT/LS) over the Asian continent is a recognized feature during the boreal summer monsoon. While there has been a debate on the role of monsoon convective intensities on the UT/LS water vapor accumulations, there are ambiguities with regard to the effects of organized monsoon convection on the spatial distribution of water vapor. We provide insights into this aspect using high precision balloon measurements of water vapor from a high-elevation site Nainital (29.4° N, 79.5° E), India, located in the Himalayan foothills and satellite retrievals of water vapor from the Microwave Limb Sounder (MLS). We also use precipitation estimates from the Tropical Rainfall Measuring Mission (TRMM) satellite (i.e., merged product 3B42 and precipitation radar 3A25 estimates of rain rate and rain type viz convective/stratiform), reanalysis circulation data, as well as numerical model simulations. We first evaluate the MLS estimates of water vapor mixing ratios with in situ high precision hygrometer balloon observations over Nainital. It is seen from our analyses of the MLS data that the LS water vapor distribution is closely linked to the organization of the South Asian monsoon convection and its influence on the UT/LS circulation. This link between LS water vapor distribution and organized monsoon convection is also captured in the in situ observations on 3 August 2016. It is evidenced that periods of organized summer monsoon convective activity over the Indian subcontinent and Bay of Bengal promote divergence of water vapor flux in the UT/LS; additionally the Tibetan anticyclonic circulation causes widespread distribution of the UT/LS water vapor. In addition to the effects of Asian monsoon convection, we also note that global climate drivers such as El Niño-Southern Oscillation (ENSO), Brewer–Dobson circulation (BDC), and Quasi-Biennial Oscillation (QBO) can contribute to nearly 38% of the UT/LS water vapor variability over the Asian monsoon region. The main result of our study indicates that widespread spatial distribution and accumulation of water vapor in the LS (about 80% of total accumulation between May and August months) tend to co-occur with organized monsoon convection, intensified divergence of water vapor flux in the UT/LS and intensified Tibetan anticyclone. On the other hand, the circulation response and LS water vapor distribution to pre-monsoon localized deep convection tend to have a limited spatial scale confined to Southeast Asia. Results from model experiments suggest that the UT/LS circulation pattern to organized monsoon convection has resemblance to stationary Rossby waves forced by organized latent heating, with the westward extending response larger by about 15° longitudes as compared to that of the pre-monsoon localized deep convection.

We present high temporal (near-annually) resolved δ18O values from absolutely dated stalagmite record that represents the Indian Summer Monsoon (ISM) rainfall variations for the Indian subcontinent spanning from 207 AD to 2014 AD. This rainfall reconstruction shows ISM varaitions for four major global climatic periods viz., Roman Warm Period (RWP), Dark Ages Cold Period (DACP), Medieval Warm Period (MWP) and Little Ice Age (LIA). Cave records from different patrs of the sub-continent synchronously show enhanced precipitation during DACP. This wet period was forced by Solar-induced El-NiNo Southern Oscillation (ENSO) and Tibetan Plateau Temperature. Cliamtic conditions were wetter during LIA than that during MWP, as the former witnessed more number of wet monsoon years. However, MWP witnessed the strongest and the weakest monsoon years in the last two millennia. The direct influence of Soalr activity on the position of Inter Tropical Convergance zone (ITCZ) might have caused the observed ISM variability of MWP. Altough ISM shows largest variability during MWP, the overall monsoon state was moving towards wetter conditions, forced by ENSO. Solar induced forcings on ENSO influenced ISM during LIA. Our results suggest of non-stationary dynamical forcings over ISM during different periods in the last two millennia.

The mid-Holocene (MH) was a warmer period, similar to the end of the 21st century climate under high emission realizations. The Indus valley civilization believed to be flourished under the expense of enhanced south Asian summer monsoon precipitation associated with the northward migration of the Inter Tropical Convergence Zone (ITCZ) during the mid-Holocene (MH). However, such an enhanced precipitation is not visible over the northwest India and Pakistan belt in future projection. The role of dynamical and various teleconnection factors behind the enhanced MH precipitation over the Indus valley region is still elusive due to the limitation of course resolution modelling efforts available so far as part of the various phases of Paleoclimate Modelling Intercomparison Projects (PMIP). To overcome this limitation, we have designed high resolution Paleo-climate simulations using a state-of-the-art variable resolution global climate model (LMDZ: Laboratoire Meteorologie Dynamique and Z stand for zoom) which configured with a 35 km spatial resolution over the South Asian region. We conducted various sensitivity experiments to understand the role of dynamics and teleconnection in enhancing monsoon precipitation over the Indus valley in addition to the MH orbital conditions. Boundary conditions from the PMIP-3, CMIP5 and HadISST datasets utilized for various sensitive experiments. High resolution, clearly demonstrates value addition in simulating the enhanced MH precipitation over Northwest India and adjoining Indus basin associated with the northward migration of the ITCZ and shift in the ascending branch of Hadley cell. We explored the role of various oceanic and atmospheric factors responsible for this enhanced Indus valley precipitation through linearized moisture budget analysis and comparing the relative strength and position of Hadley cell. By further decomposing the thermodynamic and dynamic term into their advection and divergence component, we could demonstrate the role of moisture convergence due to the strengthened atmospheric circulation through the oceanic teleconnection, which additionally plays a crucial role in enhanced MH precipitation comparing to the dynamical factors. Idealized simulation with the end of 21st century warm condition with the MH orbital forcing and various teleconnection patterns affirms that the thermodynamically induced future precipitation and circulation changes, may not be adequate to make a profound shift in the northern limit of the ITCZ towards its MH locale rather producing enhanced precipitation over the north Indian ocean and localized extreme precipitation over Indian landmass. Keywords: Indus Valley civilization, Mid-Holocene, Monsoons, Teleconnection, ITCZ and Hadley circulation

The alternation of active and break phases in Indian summer monsoon (ISM) rainfall at intraseasonal timescales characterizes each ISM season. Both tropical and mid-latitude drivers influence this intraseasonal ISM variability. The circumglobal teleconnection observed in boreal summer drives intraseasonal variability across the mid-latitudes, and a two-way interaction between the ISM and the circumglobal teleconnection pattern has been hypothesized. We use causal discovery algorithms to test the ISM circumglobal teleconnection hypothesis in a causal framework. A robust causal link from the circumglobal teleconnection pattern and the North Atlantic region to ISM rainfall is identified, and we estimate the normalized causal effect (CE) of this link to be about 0.2 (a 1 standard deviation shift in the circumglobal teleconnection causes a 0.2 standard deviation shift in the ISM rainfall 1 week later). The ISM rainfall feeds back on the circumglobal teleconnection pattern, however weakly. Moreover, we identify a negative feedback between strong updraft located over India and the Bay of Bengal and the ISM rainfall acting at a biweekly timescale, with enhanced ISM rainfall following strong updraft by 1 week. This mechanism is possibly related to the boreal summer intraseasonal oscillation. The updraft has the strongest CE of 0.5, while the Madden–Julian oscillation variability has a CE of 0.2–0.3. Our results show that most of the ISM variability on weekly timescales comes from these tropical drivers, though the mid-latitude teleconnection also exerts a substantial influence. Identifying these local and remote drivers paves the way for improved subseasonal forecasts.

Tropical convective activity represents a source of predictability for mid-latitude weather in the Northern Hemisphere. In winter, the El Niño–Southern Oscillation (ENSO) is the dominant source of predictability in the tropics and extratropics, but its role in summer is much less pronounced and the exact teleconnection pathways are not well understood. Here, we assess how tropical convection interacts with mid-latitude summer circulation at different intra-seasonal timescales and how ENSO affects these interactions. First, we apply maximum covariance analysis (MCA) between tropical convective activity and mid-latitude geopotential height fields to identify the dominant modes of interaction. The first MCA mode connects the South Asian monsoon with the mid-latitude circumglobal teleconnection pattern. The second MCA mode connects the western North Pacific summer monsoon in the tropics with a wave-5 pattern centred over the North Pacific High in the mid-latitudes. We show that the MCA patterns are fairly insensitive to the selected intra-seasonal timescale from weekly to 4-weekly data. To study the potential causal interdependencies between these modes and with other atmospheric fields, we apply the causal discovery method PCMCI at different timescales. PCMCI extends standard correlation analysis by removing the confounding effects of autocorrelation, indirect links and common drivers. In general, there is a two-way causal interaction between the tropics and mid-latitudes, but the strength and sometimes sign of the causal link are timescale dependent. We introduce causal maps that show the regionally specific causal effect from each MCA mode. Those maps confirm the dominant patterns of interaction and in addition highlight specific mid-latitude regions that are most strongly connected to tropical convection. In general, the identified causal teleconnection patterns are only mildly affected by ENSO and the tropical mid-latitude linkages remain similar. Still, La Niña strengthens the South Asian monsoon generating a stronger response in the mid-latitudes, while during El Niño years the Pacific pattern is reinforced. This study paves the way for process-based validation of boreal summer teleconnections in (sub-)seasonal forecast models and climate models and therefore works towards improved sub-seasonal predictions and climate projections.

For millennia the Indus Valley Civilizations have learned how to manage the waters of the Indus River water system. However, climate changes could have unforeseeable effects on the region's growing population, and they could hinder short- and long-term decision making regarding the emerging needs of the energy-food-water nexus. Also, changes in aspects of the variability of monsoons and in the timing and amount of snow and glacier melt may lead to extreme events, such as droughts over the Asian plains and flooding in the neighboring Himalayas. Although global and regional climate models have advanced our knowledge about future changes in the climate system, there are still uncertainties and knowledge gaps in our understanding of the precipitation systems associated with the Asian summer monsoon and the winter and pre-monsoon western disturbances. Hence understanding the summer and winter precipitation variabilities and their connections to the hydrological cycle in the Hindu-Kush-Himalayan region in general and the Indus River Basin in particular is of utmost importance for setting baseline and future timescales.

A better understanding of precipitation dynamics in the Indian subcontinent is required since India's society depends heavily on reliable monsoon forecasts. We introduce a non-linear, multiscale approach, based on wavelets and event synchronization, for unravelling teleconnection influences on precipitation. We consider those climate patterns with the highest relevance for Indian precipitation. Our results suggest significant influences which are not well captured by only the wavelet coherence analysis, the state-of-the-art method in understanding linkages at multiple timescales. We find substantial variation across India and across timescales. In particular, El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) mainly influence precipitation in the south-east at interannual and decadal scales, respectively, whereas the North Atlantic Oscillation (NAO) has a strong connection to precipitation, particularly in the northern regions. The effect of the Pacific Decadal Oscillation (PDO) stretches across the whole country, whereas the Atlantic Multidecadal Oscillation (AMO) influences precipitation particularly in the central arid and semi-arid regions. The proposed method provides a powerful approach for capturing the dynamics of precipitation and, hence, helps improve precipitation forecasting.

This study investigates the sub-synoptic scale circulation aspects associated with the extreme rainfall event occurred over the North Indian state of Uttarakhand located in the western Himalayas (WH) during the 15–18 June 2013 period. A diagnosis based on hourly ERA5 reanalyzed circulation products archived on finer grids reveals that sustenance of heavy rains during the event period is supported by a propensity of cyclonic vorticity sources channeled toward the WH region through a narrow quasi-steady conduit in the lower troposphere from the ISM circulation. The equatorward segregating mesoscale potential vorticity (PV) structures from the quasi-stationary upper level PV anomaly (trough) during the event administered two pathways for vorticity sources. The first pathway is from the base of the trough culminating into longer horizontal conduit path from the western Arabian Sea, lending perpetual cyclonic vorticity support to the ISM environment. The second pathway is from the right flank of the trough, which promotes sustained environment of deeper mesoscale convergence zone, potentially unstable atmosphere and strong ascent over the Uttarakhand region. The convergence zone is potentially viewed as a region for strong monsoon and extratropical circulation interactions to occur on finer horizontal scales of motion, where significant vertical synchronization of positive PV advection is realized during the 16–17 June 2013 period. In addition to orographic precipitation enhancements, deeper advective synchronization noticed at sub-synoptic time periods is accredited to the nearly doubling 24-h rainfall amounts in the foothill region of Uttarakhand during the event period. The ERA5 diagnosed diabatic heating additionally indicates that precipitating systems at higher (foothill) elevations contribute to upper (lower) tropospheric heat sources.