SYLLABUS

GS-3: Conservation, environmental pollution and degradation, environmental impact assessment.

Context: A new scientific study highlights that water vapour plays a stronger role than aerosols in atmospheric heating with significant implications for climate dynamics and the Indian summer monsoon.

More on the News

• The study was published in the journal Atmospheric Research and was conducted by Aryabhatta Research Institute of Observational Sciences, Nainital and the Indian Institute of Astrophysics, Bengaluru. 

• Both institutions function under the Department of Science and Technology, Government of India.

• International collaborators included the University of Western Macedonia, Greece and Soka University, Japan.

Study Region and Data Used

• The study focuses on the Indo-Gangetic Plain, which is a global hotspot of aerosol loading.

• Aerosol loading Hotspots are regions with persistently high concentrations of atmospheric aerosols (tiny solid or liquid particles suspended in the atmosphere), measured mainly through Aerosol Optical Depth (AOD).

• Data from six AERONET (Aerosol Robotic Network) ground-based observation sites were used.

• Radiative transfer simulations were carried out using the SBDART model.

• SBDART model (Santa Barbara DISORT Atmospheric Radiative Transfer) is based on DISORT (Discrete Ordinate Radiative Transfer) algorithm and is a widely used radiative transfer model that simulates how solar (shortwave) and terrestrial (longwave) radiation interact with the Earth’s atmosphere and surface.

Key Scientific Findings

• The study found that water vapour has a greater impact on atmospheric heating than aerosols because of: 

• Natural Greenhouse Effect: Water vapour, being a Dominant Greenhouse Gas, absorbs outgoing longwave (infrared) radiation very efficiently.
• Positive Feedback Mechanism: Rising temperatures increase evaporation, forming more water vapour and enhancing heat trapping.

• The radiative effects of water vapour are strongly influenced by the presence of aerosols, and its impact is more visible at the top of the atmosphere.

• Radiative effects refer to how a substance absorbs, emits, and scatters radiation, thereby influencing Earth’s energy balance.

• Water vapour radiative effects are more intense in aerosol free atmospheres.

• Aerosol water vapour interactions significantly modulate the atmospheric radiation budget.

Climate and Policy Significance

• The findings highlight the major role of water vapour in climate feedback processes.

• Water vapour affects cloud formation, precipitation, aerosol growth and atmospheric circulation.

• The study shows that ignoring water vapour can lead to inaccurate climate projections.

• It underlines the need to consider both aerosols and water vapour in climate models.

• The results are crucial for understanding regional climate dynamics and the Indian summer monsoon.

Broader Implications

• The study strengthens scientific understanding of Earth’s radiation balance.

• It highlights water vapour as a critical positive feedback factor in global warming.

• It supports improved regional climate prediction and evidence-based climate policy formulation.