Balasubramanian Govindasamy

Indian Institute of Science Bangalore | IISC · Centre for Atmospheric and Oceanic Sciences (CAOS)

Understanding the climate response to interhemispheric differences in imposed radiative forcing is crucial for solar radiative modification (SRM) investigations. While previous studies have shown that climate sensitivity to solar insolation changes imposed in the Northern (NH) versus the Southern Hemisphere (SH) is different, the underlying mechani...

Stratospheric aerosol geoengineering (SAG) is one of the several solar geoengineering options that have been proposed to counteract climate change. In the case of SAG, reflective aerosols injected into the stratosphere would reflect more sunlight and cool the planet. When assessing the potential efficacy and risks of SAG, the sensitivity of tropica...

Understanding the climate and carbon cycle response to negative CO2 emissions is important for developing climate mitigation strategies that aim to limit global warming to a specific threshold. In this study, using a coupled climate and carbon cycle model, a novel set of nine stylized simulations are conducted with cumulative emissions of 1,000 GtC...

Stratospheric aerosol geoengineering (SAG) has been proposed as one of the potential options to offset the impacts of anthropogenically induced climate change. Previous modelling studies have shown that the efficacy of the cooling via SAG increases with altitude of the aerosol layer. It has been also shown that the stratospheric heating associated...

In this review, we assess scientific evidence for tipping points in ocean and atmosphere circulations. The warming of oceans, modified wind patterns and increasing freshwater influx from melting ice hold the potential to disrupt established circulation patterns. The literature provides evidence for oceanic tipping points in the Atlantic Meridional...

This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgre...

Monsoon low pressure systems (LPS) are synoptic-scale disturbances that form along the quasi-stationary trough of the larger-scale South Asian summer monsoon, producing a large fraction of total monsoon precipitation. Here, we use an Earth system model to investigate the influence of Tibetan and Himalayan orography (THO) on mean monsoon strength an...

In this study, using the NCAR Community Earth System Model (CESM1.2.2), we investigate the changes in the characteristics of the summer monsoon low pressure systems (LPS) over India in a twenty-first century climate change simulation corresponding to the RCP8.5 scenario. A slight weakening in monsoon circulation and an increase in mean summer monso...

The stability and resilience of the Earth system and human well-being are inseparably linked1–3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, wate...

Afforestation and reduction of fossil fuel emissions are two major components of climate mitigation policies. However, their effects on the Earth's climate are different because a reduction of fossil fuel emissions directly alters the biogeochemical cycle of the climate system and modifies the physics of the atmosphere via its impact on radiation a...

Stratospheric Aerosol Geoengineering (SAG) is one of the solar geoengineering approaches that have been proposed to offset some of the impacts of anthropogenic climate change. Past studies have shown that SAG may have adverse impacts on the global hydrological cycle. Using a climate model, we quantify the sensitivity of the tropical monsoon precipi...

Previous studies have shown that climate sensitivity, defined as the global mean surface temperature change per unit radiative forcing, is smaller for solar radiative forcing compared to an equivalent CO 2 radiative forcing. We investigate the causes for this difference using the NCAR CAM4 model. The contributions to the climate feedback parameter,...

Climate records of ratios of stable water isotopes of oxygen (δ18O) are used to reconstruct the past Indian monsoon precipitation. Identifying the sources of water vapor is important in understanding the role of monsoonal circulation in the δ18O values, to aid in monsoon reconstructions. Here, using an isotope-enabled Earth system model, we estimat...

Afforestation and reduction of fossil fuel emissions are two major components of climate mitigation policies. However, their effects on the earth’s climate are different because reduction of fossil fuel emissions directly alters the biogeochemical cycle of the climate system, while afforestation causes biophysical changes in addition to changes in...

The biophysical (land surface physical characteristics) and biogeochemical (chemical characteristics) effects of land cover change (LCC) contributed substantially to the historical climate change. Future land-use activity is expected to increase to meet the growing demand for food, fiber, and energy with uncertain sign of its effect on net climate...

Climate change, land use land cover (LULC), population, industries, and sewage treatment are factors that can strongly influence river water quality. This paper uses a coupled hydrological-water quality simulation model to assess the influence of each of these drivers on the most polluted river stretch of the Ganga River. The water quality model QU...

The industrialized stretch of Kanpur is considered to be one of the most polluted stretches of the Ganga River, with untreated sewage, industrial discharge, and agricultural runoff. Risk assessment studies on water quality for future scenarios are limited for this stretch of the river. In this study, we assess the effect of climate change on water...

Climate intervention through deliberate injection of sulfate aerosols into the stratosphere is one of the proposed solar radiation modification options to counteract some of the adverse effects of climate change. Although this approach can offset global mean temperature change, several studies have shown that there will be large residual and overco...

Carbon dioxide emissions from deforestation disturbance (e.g., clear-cutting, forest fires) are in the same units as carbon dioxide emissions from fossil fuels. However, if the forest is allowed to regrow, there is a large difference between climate effects of that forest disturbance and climate effects of fossil CO 2 . In this study, using a set o...

Monsoon low pressure systems (LPS) during the summer monsoon season (June–September) over India are a lifeline for the agriculture‐dependent country. We use the Community Earth System Model (CESM1.2.2) to simulate the LPS characteristics (genesis, propagation direction, tracks, intensity, and precipitation) over India and the Bay of Bengal and anal...

Stratospheric aerosol injection is one of the most widely studied solar radiation modification methods to reduce some effects of anthropogenic warming. We perform idealized simulations to analyze climate response to different latitudinal and altitudinal distributions of additional stratospheric sulphate aerosols. We analyze climate response to both...

The Working Group I (WGI) contribution to the Intergovernmental Panel on Climate Change Sixth Assessment Report (AR6) assess the physical science basis of climate change. As part of that contribution, this Technical Summary (TS) is designed to bridge between the comprehensive assessment of the WGI Chapters and its Summary for Policymakers (SPM). I...

In this study, we perform idealized climate model simulations to assess the relative impacts of an increase in local black carbon (BC) aerosols (located over the Indian region) and the remote BC aerosols (located outside the Indian region) on the summer monsoon precipitation over India. We decompose the precipitation changes into fast adjustments t...

Keeping the Earth system in a stable and resilient state, to safeguard Earth's life support systems while ensuring that Earth's benefits, risks, and related responsibilities are equitably shared, constitutes the grand challenge for human development in the Anthropocene. Here, we describe a framework that the recently formed Earth Commission will us...

The South Asian summer monsoon brings copious rain to agriculture-dependent country India and bulk of the precipitation in central India is attributed to monsoon low pressure systems (LPS). Large uncertainty exists in the statistics of LPS during the historical period and in future projections. In this study, we have developed an LPS tracking appro...

Solar radiation modification has been suggested as a backup option to reduce anthropogenic warming. Marine cloud brightening (MCB) and ocean albedo modification (OAM) are two proposed approaches to intentionally reflect sunlight back to space over oceanic regions. Using the NCAR Community Earth System Model, we compare climate response to MCB and O...

The Working Group I (WGI) contribution to the Intergovernmental Panel on Climate Change Sixth Assessment Report (AR6) assess the physical science basis of climate change. As part of that contribution, this Technical Summary (TS) is designed to bridge between the comprehensive assessment of the WGI Chapters and its Summary for Policymakers (SPM). It...

The variation of stable water isotopes (δ18O, δD) in climate archives is an important proxy to understand the evolution of South Asian monsoon (SA) precipitation over the Holocene. In this study, using an isotope-enabled climate-model, we examine the responses of water isotopes in precipitation over the SA region to orbital changes in the early to...

A number of radiation modification approaches have been proposed to counteract anthropogenic warming by intentionally altering Earth's shortwave or longwave fluxes. While several previous studies have examined the climate effect of different radiation modification approaches, only a few have investigated the carbon cycle response. Our study examine...

Abstract Solar geoengineering by deliberate injection of sulfate aerosols in the stratosphere is one of the proposed options to counter anthropogenic climate warming. In this study, we focus on the effect of a specific microphysical property of sulfate aerosols in the stratosphere: hygroscopic growth—the tendency of particles to grow by accumulatin...

Reduction of surface temperatures of the planet by injecting sulfate aerosols in the stratosphere has been suggested as an option to reduce the amount of human-induced climate warming. Several previous studies have shown that for a specified amount of injection, aerosols injected at a higher altitude in the stratosphere would produce more cooling b...

Terrestrial and oceanic carbon sinks together sequester >50% of the anthropogenic emissions, and the major uncertainty in the global carbon budget is related to the terrestrial carbon cycle. Hence, it is important to understand the major drivers of the land carbon uptake to make informed decisions on climate change mitigation policies. In this pape...

Plain Language Summary Major volcanic eruptions are considered as natural analogues for stratospheric sulfate aerosol geoengineering that aims to cool the climate by increasing the burden of stratospheric sulfate aerosols. Volcanic eruptions produce a layer of sulfate aerosols that stays in the stratosphere for a couple of years, whereas geoenginee...

Using idealized climate model simulations, we investigate the effectiveness of black carbon (BC) aerosols in warming the planet relative to CO2 forcing. We find that a 60-fold increase in the BC aerosol mixing ratio from the present-day levels leads to the same equilibrium global mean surface warming (∼4.1K) as for a doubling of atmospheric CO2 con...

A multi-model-based assessment is made to assess the trends and variability in the land carbon uptake in India during the period 1901–2010. Data from nine models, used in a recent land surface model inter-comparison project called TRENDY, are used for this purpose. Our analysis is focused on the trends and variability in the net primary productivit...

Reduction of surface temperatures of the planet by injecting sulfate aerosols in the stratosphere has been suggested as an option to reduce the amount of human-induced climate warming. Several previous studies have shown that for a specified amount of injection, aerosols injected at a higher altitude in the stratosphere would produce more cooling b...

The Himalayan glaciers are a major source of Perennial River systems in South Asia and the retreat of these glaciers under climate change could directly affect millions of people, who depend on them. In this study, we assess the glacier mass balance, area and volume changes at the basin scale for the Chandra Basin in the western Himalaya due to pro...

Anthropogenic influences and global climate change are expected to alter the land carbon stocks in the future. In this modeling study, using the NCAR Community Earth System Model (CESM), we assess the relative importance of CO2 fertilization, nitrogen deposition, climate change, and land use and land cover changes (LULCC) on the land carbon uptake...

We qualitatively and quantitatively assessed the factors related to vegetation growth using Earth system models and corroborated the results with historical climate observations. The Earth system models showed a systematic greening by the late 21st century, including increases of up to 100% in Gross Primary Production (GPP) and 60% in Leaf Area Ind...

Satellite data show increasing leaf area of vegetation due to direct factors (human land-use management) and indirect factors (such as climate change, CO2 fertilization, nitrogen deposition and recovery from natural disturbances). Among these, climate change and CO2 fertilization effects seem to be the dominant drivers. However, recent satellite da...

Earth observations collected by remote sensors provide unique information to our ever-growing knowledge of the terrestrial biosphere. Yet, retrieving information from remote sensing data requires sophisticated processing and demands a better understanding of the underlying physics. This paper reviews research efforts that lead to the developments o...

This article presents a brief account of scientific research into solar geoengineering in India in the last decade. In recent years, solar geoengineering has been proposed as an option to ameliorate the detrimental impacts of climate change in case the required emissions reductions do not take place rapidly. Hundreds of research papers have been pu...

In this study, using idealized step-forcing simulations, we examine the effective radiative forcing of CH4 relative to that of CO2 and compare the effects of CH4 and CO2 forcing on the climate system. A tenfold increase in CH4 concentration in the NCAR CAM5 climate model produces similar long term global mean surface warming (~ 1.7 K) as a one-thir...

Geoengineering has been proposed as a backup approach to rapidly cool the Earth and avoid damages associated with anthropogenic climate change. In this study, we use the NCAR Community Earth System Model to conduct a series of slab-ocean and prescribed sea surface temperature simulations to investigate the climate response to three proposed radiati...

Arctic geoengineering wherein sunlight absorption is reduced only in the Arctic has been suggested as a remedial measure to counteract the on-going rapid climate change in the Arctic. Several modeling studies have shown that Arctic geoengineering can minimize Arctic warming but will shift the Inter-tropical Convergence Zone (ITCZ) southward, unless...

To the understand future state of glaciers at river-basin scale in the Himalaya. The results of this analysis will help policy makers and downstream populations to prepare for near-future risks due to looming water scarcity & geophysical hazards.

In this study, we examine the statistics of precipitation extreme events in a model simulation of solar radiation management (SRM) geoengineering. We consider both intensity and frequency-based extreme indices for precipitation. The analysis is performed over both large-scale domains as well as regional scales (22 Giorgi land regions). We find that...

In this study, we examine the statistics of temperature extremes in a model simulation of solar radiation management (SRM) geoengineering. We consider both intensity and frequency-based extreme indices for temperature. The analysis is performed over both large-scale domains as well as regional scales (22 Giorgi land regions). We find that temperatu...

In this study, we linearize the surface energy budget equation which disentangles indirect effects (due to changes in downward short- and long-wave radiation and air temperature) from direct biophysical effects (due to changes in surface albedo, evapotranspiration and roughness length) of deforestation on land surface temperature. We apply this for...

Forests are subjected to stress from climatic and non-climatic sources. In this study, we have reported the results of inherent, as well as climate change driven vulnerability assessments for Indian forests. To assess inherent vulnerability of forests under current climate, we have used four indicators, namely biological richness, disturbance index...

An improved understanding of fresh water stored in the Himalaya is crucial for water resource management in South Asia and can be inferred from glacier mass-balance estimates. However, field investigations in the rugged Himalaya are limited to a few individual glaciers and short duration. Therefore, we have recently developed an approach that combi...

Solar geoengineering has been proposed as a backup plan to offset some aspects of anthropogenic climate change if timely CO2 emission reductions fail to materialize. Modeling studies have shown that there are trade-offs between changes in temperature and hydrological cycle in response to solar geoengineering. Here we investigate the possibility of...

Arctic geoengineering wherein sunlight absorption is reduced only in the Arctic has been suggested as a remedial measure to counteract the on-going rapid climate change in the Arctic. Several modeling studies have shown that Arctic geoengineering can minimize Arctic warming but will shift the Inter-tropical Convergence Zone (ITCZ) southward, unless...

For the first time we are providing basin wide annual mass balance series for more than two decades.

The empirical "amount effect" observed in the distribution of stable water isotope ratios in tropical precipitation is used in several studies to reconstruct past precipitation. Recent observations suggest the importance of large-scale organized convection systems on amount effect. With a series of experiments with Community Atmospheric Model versi...