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.