Tag: rainfall

IIT Kharagpur discovers Isotopes in Fossil Trees from Deccan Trap Lavas that Indicate Wetter Future Due to Global Warming

 

Deccan Trap lava hills in Western Ghats (Left) and columnar basaltic lavas (Right) which erupted 66 million years back killing dinosaurs and most life on earth.

A team of scientists from IIT Kharagpur and Academia Sinica, Taipei have indeed found evidence of triple oxygen isotopes of intertrappean fossil woods that led to very high annual rainfall during the catastrophic volcanism of Deccan trap that erupted in India about 66 million years back. The eruption drove a major mass extinction killing nearly 80% of all species of animals including the Dinosaurs. The depleted values of the oxygen isotopes suggest a higher tropical rainfall (1600 mm/y) in island India during terminal Cretaceous period. The increase in rainfall and its waning in the early Palaeocene closely follows change in palaeo-atmospheric pCO2 suggesting a possible underlying link. The inferred rainfall increase is consistent with modern climate models and palaeobotanical evidence.

Prof. Anindya Sarkar
Department of Geology and Geophysics
IIT Kharagpur 

“The available records of the atmospheric CO2 concentration and temperature over both land and ocean during the time of Deccan Trap eruption were analyzed. This was a period of cataclysm. All around the central and western India, Deccan trap lavas were erupting spewing huge amount of CO2 from deep interior of the earth thus increasing the then atmospheric CO2 concentration to as high as 1000 ppm (parts per million). The land and ocean temperatures increased by ~13°C and ~4°C respectively. It was a hot earth and unbearable for life. The rainfall, both before and after this high CO2 concentrated earth was just as normal as today. This was an ancient analogue of what our future greenhouse earth could be,” said IIT Kharagpur’s Prof. Anindya Sarkar of Geology and Geophysics who led the research.

Fossil fuel emission has increased the CO2 from pre‐industrial level of 280 ppm to ~420 ppm in 2023. Climate models suggest that a doubling of CO2 will intensify the atmospheric circulation and consequently the rainfall. Many experts, however, believe that the climate change due to such fast rate of global warming is now irreversible and another mass extinction is just imminent, added Prof. Sarkar.

66 million year old fossil trees from the lake sediments within Deccan lava flows and microscopic photograph of vascular bundles in palm tree (left), and Scanning electron microscopic image of the cellular structures of fossil palm trees (right)

The 2023 AR6 report by the Intergovernmental Panel on Climate Change (IPCC) warns if the CO2 emission and global warming continues unabated, annual wettest day precipitation will increase by manifold across all continents. Monsoonal precipitation associated with tropical cyclones over India will also increase by 40%. While these predictions are made through climate models, they can only be tested by studying the rainfall record in the past when the earth went through natural warming phase due to high CO2 emission.

The laser ablation system developed at IIT Kharagpur capable of analyzing ultra‐low quantity of rare isotopes of oxygen in silicate phases (shown by arrow)

 

“Deccan Traps are one of the most voluminous basaltic volcanic lavas erupted on Earth covering over 500,000 sq. km of the west‐central Indian subcontinent. We retrieved the past rainfall by analyzing oxygen isotopes in fossilized trees those grew around the lakes formed over the basaltic lavas of Deccan traps. It was as if an ancient forest was fossilized. These lakes were formed during the quiescent period between two successive lava flows. Known as intertrappeans, the sediments in these lakes contain abundant plant, frog and fish fossils. The trees were exceptionally well preserved and buried immediately after they fell in lake beds making them robust climate recorder,” added Prof. Sarkar.

Prof. Mao Chang Liang
Academia Sinica

“We studied very high magnification images of several palm trees from these lake sediments and found that their internal cellular structures are preserved just like modern trees,” said collaborator Prof. Mao Chang Liang from Academia Sinica.

There is considerable debate about the effect of future global warming on tropical precipitation. Interpretations from the global climate models differ due to an inadequate understanding of the processes controlling rainfall and associated feedback. The robustness of the predictions is also limited due to the lack of deep time data of precipitation in a high CO2 and warmer globe that existed in the geological past.

Sangbaran Ghoshmaulik
Ph.D Student
IIT Kharagpur

“Getting information about the past rainfall is tricky. We used a very novel and new technique of Laser beam as well as NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) where the fossil trees were analyzed for all the three isotopes of oxygen namely, 16,17, and 18. The isotopes in the fossil trees record the isotopic composition of the lake water derived from rainfall. Analyzing isotopes of mass 17 is difficult since it occurs in extremely small quantity in natural materials. Globally there are only three or four laboratories those can reliably do this job. It took nearly four years for us to develop this method but once done the results were very startling” said Sangbaran Ghoshmaulik, a Ph.D student at IIT Kharagpur and the lead author of the paper.

The Cretaceous period represents an example of hot deep sea and land temperatures often exceeding 10 °C and 30 °C respectively and high CO2 earth. The intertrappean sediments deposited during the voluminous basaltic outpouring of end-Cretaceous Deccan volcanism in India provide a unique repository to infer the magnitude of tropical precipitation during an enhanced greenhouse period.

Prof. Sourendra Bhattacharya
Co‐author of the Paper
IIT Kharagpur

“Excepting the arid/semi‐arid regions, the modern annual rainfall over large part of peninsular India on an average is about 1000‐1200 mm. Our data suggested that these fossil trees recorded 1800‐1900 mm/year rainfall. This is exactly what the IPCC predicts in case of a future extreme 4oC warming of the planet,” said Prof. Sourendra Bhattacharya, a co‐author of the paper. The study has just been published online in prestigious Elsevier Journal Chemical Geology.

Link of the paper:
https://www.sciencedirect.com/science/article/abs/pii/S0009254123002991

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Contact person : Prof. Anindya Sarkar, Department of Geology and Geophysics, IIT Kharagpur
Email: sarkaranindya@hotmail.com

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IIT Kharagpur Study Predicts River Basin-wise Agricultural Droughts-North India Shows High Vulnerability

With inputs from Rituparna Chakraborty

Highlights:

  • The study predicts future status climate change-induced agricultural droughts across India.

  • More intense droughts in North, North-East and Central India are expected as compared to South India.

  • About 20 and 50% of the area in India is expected to face extreme and moderate agricultural droughts, respectively, by the end of the 21st century.

Farmers in India’s north, north-east and central regions may have to be more cautious of agricultural droughts in the future – reveals IIT Kharagpur study. The data shows a geographically contrasting change in future drought patterns that indicates more intense agricultural drought in north, north-east, and central India as compared to south India due to changing climate. 

The study conducted by research scholar Mayank Suman from the School of Water Resources and Dr. Rajib Maity, Associate Professor at the Department of Civil Engineering at IIT Kharagpur has been published in the Journal of Water and Climate Change. The researchers have identified vulnerable basins, out of a total of 226 sub-basins across India, considering the future agricultural drought. The area under drought is also expected to increase which might lead to about 20 to 50% of mainland India suffering from extreme to moderate agricultural drought conditions respectively, by the end of this century.

Trend of SSMI series for different future periods. The maps show the basin-wise trend of agricultural droughts in entire ‘future’ period upto 2100 and three epochs: E1 (2006-2035), E2 (2036-2070), and E3 (2071-2100) for the worst climate change scenario.

“Sub-basins in Northern India are expected to have a longer time under drought conditions followed by sub-basins in central India. Sub-basins in the Gangetic plain were also observed to exhibit high vulnerability to extreme drought conditions in future,” said Mayank Suman.

The recent studies on meteorological drought suggest more intense and frequent drought events due to changing climate.

“With climate change, air temperature is expected to increase, resulting in a drying tendency in soil moisture and streamflow along with higher and intense precipitation. The prediction of an increase in the area under drought has been made due to these probable changes. Many studies suggest that drought is expected to become more severe and frequent, and the areas under drought are expected to increase with local variation in the future,” remarked Prof. Rajib Maity.

With India’s steep dependence on agriculture and allied economies [18% of GDP, Source: Ministry of Statistics and Programme Implementation, Govt. of India, 2021], monitoring, assessment, and prediction of agricultural drought are of immense importance.

“With the extreme drought conditions having a possible adverse effect on food production in identified regions, policymakers would find our findings useful for future planning and preparedness in terms of agricultural productivity,” added Prof. Maity.

The researchers predicted the drought status using the wavelet-based drought temporal consequence modelling of meteorological drought with the best performing bias-corrected Coordinated Regional Downscaling Experiment (CORDEX) simulations, selected by Multi-Criteria Decision- Making frameworks. They used the Standardized Soil Moisture Index as the drought characterizing index alongwith most of the existing studies on meteorological droughts are analyzed using the indices, such as Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, and the Palmer Drought Severity Index.  

About IIT Kharagpur: Indian Institute of Technology Kharagpur is a higher educational institute known globally for its graduate output and affordable technology innovations. Set up in 1951 in a detention camp as an Institute of National Importance, the Institute is ranked among the top five in India and has been awarded Institute of Eminence by the Govt. of India in 2019. The key areas of research of IIT Kharagpur are Affordable Healthcare Technologies, Advanced Manufacturing, Advanced Transportation, Precision Agriculture and Food Technology, Cyberphysical Systems, Ecology & Environment, Mining, Water Resources and Architecture. The Institute is engaged in several international and national mission projects and ranks significantly in research output including 50-100 IPR filed annually and about 2000 research publications in top journals and conferences. At present, the Institute has about 750 full-time equivalent faculty members, more than 14000 students and over 70000 Alumni. For more information visit: www.iitkgp.ac.in

Media Contact: Dr. Rajib Maity, Associate Professor, Email: rajib@civil.iitkgp.ac.in, Ph: +91-3222-283442

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Climate Change Signals from North-Eastern India, the Wettest Place on Earth

In a recent study, researchers from IIT Kharagpur have observed a significant change in the rainfall in the northeast in general and specifically at the wettest place on Earth, Cherrapunji-Mawsynram.

The researchers observed rainfall changes in the past century (1901–2019) over the wettest place on the Earth and unveiled the first evidence for the signals of climate change and anthropogenic influence on rainfall changes in the region.

Image: The figure shows the study region and rainfall received at Cherrapunji and Mawsynram in the past 50 years. The spatial change in rainfall shifted the wettest place on the Earth from Cherrapunji to Mawsynram in the early 1980s.

The analysis of 119 years of rainfall data at 17 stations in Northeast India revealed that most of the stations show negative trends in rainfall, the highest in the summer monsoon and the smallest in the winter. A clear shift in the rainfall pattern is observed in the mid-1970s. This abrupt shift in the rainfall can be attributed to the climate shift that occurred in the Pacific Ocean.

The large variability and rapid warming associated with climate change in the equatorial Indian Ocean and associated atmospheric circulation patterns, and the changes in land use/land cover are the main reasons for the inter-annual variability and negative trends in the rainfall in the northeast region, particularly at Cherrapunji and Shillong.

The seasonal rainfall cycles at these locations are also found to be changed one month ahead as compared to that before 1973. The spatial shift in the rainfall from Cherrapunji to Mawsynram in the early 1980s can also be viewed as a part of the above-mentioned temporal change and the westward movement of rainfall there.

The expansion of western subtropical Pacific high is another reason for this rainfall pattern change.

“The analyses uncover signals of regional climate change in India. Since the changes in the rainfall amount would affect drinking water, irrigation, agriculture, energy production and the economy of our country, this study cautions us about the impact of imminent climate change in our country,” says researcher Dr. J Kuttippurath, Assistant Professor, Centre for Oceans, Rivers, Atmosphere and Land Sciences (CORAL). 
Northeast India houses about 64% forest, 30% under the Brahmaputra valley and the rest has steep slopes, hills and mountains. The region has the highest vegetation cover in India and is one of the 18 biodiversity hotspots of the world; indicating the importance of the region in terms of its greenery and climate change sensitivity. Agriculture and allied activities form the backbone of the economy in the region, where more than 60% of the crop area is under rain-fed agriculture.
“The northeast region is well known as the wettest region of the world because it receives nearly 2000 mm of rainfall annually, which is about three times higher than the mean annual rainfall of India. Furthermore, the population of this region mainly depends on agriculture and horticulture, which is fed by the seasonal rainfall and therefore, any change in the rainfall would alter the economy and affect the well-being of the society,” remarked Prof. Madan Kumar Jha, Professor, Dept. of Agricultural and Food Engineering.
Citation J Kuttippurath et al 2021 Environ. Res. Lett. 16 024018, Journal: Environmental Research Letters [Impact Factor: 6.09], DOI: https://doi.org/10.1088/1748-9326/abcf78

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About IIT Kharagpur: Indian Institute of Technology Kharagpur is a higher educational institute known globally for its graduate output and affordable technology innovations. Set up in 1951 in a detention camp as an Institute of National Importance, the Institute is ranked among the top five in India and has been awarded Institute of Eminence by the Govt. of India in 2019. The key areas of research of IIT Kharagpur are Affordable Healthcare Technologies, Advanced Manufacturing, Advanced Transportation, Precision Agriculture and Food Technology, Cyberphysical Systems, Ecology & Environment, Mining, Water Resources and Architecture. The Institute is engaged in several international and national mission projects and ranks significantly in research output including 50-100 IPR filed annually and about 2000 research publications in top journals and conferences. At present, the Institute has about 750 full-time equivalent faculty members, more than 14000 students and over 70000 Alumni. For more information visit: www.iitkgp.ac.in

New Indian Monsoon Rainfall Prediction Model Developed by IIT KGP Researchers

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Researchers from Centre for Oceans, Rivers, Atmosphere and Land Sciences (CORAL) of IIT KGP have developed a new statistical model, which can be used to predict variability and trends in rainfall over different climate regions of India taking into consideration both local and remote factors causing weather change.

Many of these, local and remote, factors that affect weather conditions have been known to the scientific community. However, most weather forecast models typically consider local factors or a single factor that affects rainfall or use of statistical models of correlation to establish the impact of various factors. Because of this there used to be significant uncertainties in such predictions as each independent factor has a certain impact, which may not match with actual conditions.

“In our model we have used the multiple linear regression technique to assess contributions of different remote and local climate forcing to seasonal and regional inhomogeneity in rainfall. It removes the impact of individual factors to find the trends in rainfall. The model has three advantages; it can be used to find the contribution of individual factors to the rainfall and can be applied to estimate the trends and variability of rainfall. Apart from these, the model can predict any type of weather conditions, anywhere in the world only by changing the relevant factors affecting the changes. For instance, we have used a similar model for estimating trends in atmospheric trace gases such as ozone,” said Dr. Prijitha J. Nair, the lead researcher, who conceived and coordinated this study.

The novelty of the model has been reported through a research paper “The local and global climate forcing induced inhomogeneity of Indian rainfall” in the much-coveted Scientific Reports by the Nature.

“Our study finds that the Summer Monsoon Rainfall variability is governed by the surface temperatures of the Eastern Pacific, Central Pacific, Atlantic and the north Indian Oceans, and equatorial zonal winds. However, the winter Monsoon Rainfall variability is largely controlled by the surface temperature of the North Atlantic and extratropical oceans,” explained co-researcher Prof. Jayanarayanan Kuttippurath.

The model, which has been developed using data over a period of 38 years, has also predicted significant changes in Indian rainfall in a perspective of global climate change. The data analyses conducted during the study revealed significant positive trends (0.43mm/day/dec) in the North West for summer rainfall during the 1979–2017 period.

“There are scientific evidences of major climate shifts over centuries. These do not happen overnight but through gradual changes in weather conditions over time. The data shows there has been an incremental shift of Indian monsoon from east to west. However, this would require further studies,” said Prof. Arun Chakraborty, who supervised the research.

Dr. Hamza Varikoden, a scientist from the Indian Institute of Tropical Meteorology (IITM), Pune, and Dr. P. A. Francis, a scientist in the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad (both are from the Ministry of Earth Sciences and are renowned for their significant contributions to Indian Monsoon research), are the other researchers participated in the study.