Central Idea

A team of scientists from IIT Kharagpur has discovered evidence of exceptionally high annual rainfall during the volcanic activity that formed the Deccan Traps in India around 66 million years ago.
Using a new technique called Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS), the researchers analyzed the isotopic composition of fossil trees from the Cretaceous period.
They determined the isotopic composition of the rainfall-derived lake water.

Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS)

NanoSIMS is an advanced analytical technique to determine the composition and distribution of elements and isotopes at a microscopic scale.
It allows for high-resolution imaging and quantitative analysis of samples.
The technique involves bombarding the sample surface with a focused beam of primary ions.
This causes the ejection of secondary ions from the sample surface.
The secondary ions are collected and analyzed using a mass spectrometer.
The mass spectrometer separates the ions based on their mass-to-charge ratio and measures their abundance.

New Technique: The team used Nanoscale Secondary Ion Mass Spectrometry to analyze oxygen isotopes in fossil trees and measure the isotopic composition of the lake water derived from rainfall.
Depleted Oxygen Isotopes: The analysis revealed depleted oxygen isotope values, indicating higher tropical rainfall in India during the terminal Cretaceous period.
Link to Paleoclimatic Changes: The increase in rainfall closely corresponded to changes in paleo-atmospheric carbon dioxide levels, suggesting a potential underlying link between the two.

Atmospheric Carbon Dioxide Concentration: The eruption of Deccan Trap lavas released a significant amount of carbon dioxide, raising atmospheric levels to as high as 1,000 ppm.
Comparison to Modern Rainfall: The data from fossil trees indicated an annual rainfall of 1,800-1,900 mm, exceeding the average modern rainfall of 1,000-1,200 mm in most parts of peninsular India.
Climate Change Predictions: The findings align with predictions made by the Intergovernmental Panel on Climate Change (IPCC) for extreme warming scenarios, suggesting a correlation between high carbon dioxide levels and increased rainfall.

Rising Carbon Dioxide Levels: Fossil fuel emissions have raised carbon dioxide levels from 280 ppm to about 420 ppm in 2023.
Impact on Rainfall: Climate models indicate that doubling carbon dioxide levels will intensify atmospheric circulation and subsequently increase rainfall.
IPCC AR6 Report: The report warns of a significant increase in the wettest day precipitation and tropical cyclone-associated rainfall if carbon dioxide emissions continue to rise unabated.

The study provides evidence of high rainfall during the volcanic activity that formed the Deccan Traps in India millions of years ago.
The findings suggest a correlation between elevated carbon dioxide levels and increased rainfall, supporting predictions made by climate models for future climate change scenarios.